Hydrothermal Activity around the Mienhua submarine volcano in the northern margin of the Southern Okinawa Trough

Hydrothermal Activity around the Mienhua submarine volcano in the northern margin of the Southern Okinawa Trough | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Hydrothermal Activity around the Mienhua submarine volcano in the northern margin of the Southern Okinawa Trough Ching-Hui Tsai, Shu-Kun Hsu, Hsiao-Shan Lin, Song-Chuen Chen, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4913834/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract Hydrothermal vents can be detected using echo sounders. Here, we employed a deep-tow side-scan sonar and sub-bottom profiler to analyze the seabed features associated with hydrothermal activity near the Mienhua submarine volcano (MHV). The MHV is located in the northern margin of the southern Okinawa Trough back-arc basin. Our deep-tow sub-bottom profiler data show an upward hydrothermal fluid activity in the seabed, confirming the active hydrothermal circulation around the MHV. Widespread acoustic transparent zones are found in the upper strata, ascribed to the intrusion of hydrothermal fluid into high porosity sediment layers. In the area where acoustic transparent zones exist, the strata tilt towards the summit of the MHV. The strata influenced by the intrusion of hydrothermal fluids may create minor normal faults or fractures. These faults provide new hydrothermal fluid pathways to spread outwards. The weakened upper strata due to the hydrothermal fluids may finally collapse because of the gravity instability. The hydrothermal activity in the western portion of the MHV is no longer active. In contrast, the hydrothermal activity in the eastern portion of the MHV is rigorous and is associated with the widespread hydrothermal vents, gas flares and chimneys. The area of potential hydrothermal mineralization near the seabed of the MHV is estimated to be ~30 km². southern Okinawa Trough Mienhua submarine volcano hydrothermal Activity side-scan sonar sub-bottom profiler hydrothermal flare chimney Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Highlights 1. Upward migration of hydrothermal fluids has produced chimney structures and acoustic transparent zones in strata. 2. The hydrothermal activity in the western MHV is no longer active, causing strata subsidence. 3. The hydrothermal activity is strong in the eastern MHV. 1. Introduction Located along the eastern edge of the Eurasian Plate, the Okinawa Trough is an active back-arc basin caused by the subduction of the Philippine Sea Plate beneath the Eurasian Plate (Lee et al., 1980 ; Kimura, 1985 ; Letouzey and Kimura, 1986 ; Sibuet et al., 1987 , 1995 , 1998 ; Hsu et al., 2013 ; Tsai et al., 2021 ). The Okinawa Trough extends from Kyushu Island in southwest Japan to the Ilan Plain in northeast Taiwan. It can be divided into the Southern Okinawa Trough (SOT), the Middle Okinawa Trough (MOT), and the Northern Okinawa Trough (NOT). The segmentations are based on the structural boundaries of the Tokara Fault and the Kerama Gap (Kodaira et al., 1996 ; Shinjo et al., 1999 ; Fabbri et al., 2004 ; Gungor et al., 2012 ). The SOT is under a fast rifting because of the post-collision and transition from collision to subduction of the Philippine Sea Plate (Hsu, 2001 ; Tsai et al., 2021 ). However, the actual back-arc rifting of the Okinawa Trough terminates near 122 o 20’E (Tsai et al., 2021 ). To the west of 122 o 20’E, the former NE-SW trending structures of the proto-Taiwan mountain belt are still evident (Tsai et al., 2021 ). Due to the southward migration of the southern Ryukyu arc and the rollback of the Philippine Sea Plate, the back-arc region undergoes substantial tectonic extension. This extension leads to pronounced hydrothermal activity in the Southern Okinawa Trough (SOT) region, where intense interactions between geological processes drive the formation of hydrothermal systems. These systems contribute significant heat and mass transfer from the Earth's interior, fostering unique chemical and biological environments. The resulting hydrothermal vents and associated mineral deposits offer valuable insights into the dynamics of seafloor spreading and the complex interplay between tectonic stress and magmatic activity. Volcanism or hydrothermal activities are very active and mainly distributed along the central depression or in the southern portion of the SOT (Tsai et al., 2021 ). In contrast to most submarine volcanoes in the central depression of the SOT, the Mienhua Submarine Volcano (MHV) is located in the northern margin of the SOT (Fig. 1 a). The lower reaches of the Mienhua Submarine Canyon (MHC) flow through the north side of the MHV (Fig. 1 b). Seafloor rift valleys and mid-ocean ridges are tectonic landforms due to the divergent movement of Earth's tectonic plates. These features occur in geologically active regions, making them common sites for forming hydrothermal vents. Crustal fractures of faults provide pathways to facilitate the development of hydrothermal circulation. Hydrothermal circulation system observations mainly focus on hydrothermal flares (Massoth et al., 1988 ; Morton et al., 1956 ). Hydrothermal flares are generated when superheated water within the Earth's crust is expelled through vent openings due to pressure differences. During the ascent of the flare, surrounding seawater continuously mixes with the hydrothermal fluid, causing the flare to dissipate until the upward force balances with the surrounding water; at this point, the flare phenomenon dissipates laterally. In regions with active hydrothermal circulation, deep volcanic materials are carried out by the hot water, creating areas with smoke-like appearances. When hydrothermal fluids carry heavy metals such as manganese and iron, "Black Smokers" could be formed (Tivey et al., 1995 ). Black smokers are significant conduits for exchanging materials between seawater and the crust. To understand the distribution of hydrothermal activity in the SOT back-arc basin, Tsai et al. ( 2019 ) used a 38 kHz single-beam echo sounder (SBES) to observe gas bubbles out of the seabed associated with hydrothermal activity. They detected a total of 266 acoustic images indicative of active hydrothermal vents, including those in the MHV study area (marked by green dots in Fig. 1 b). Tsai et al. ( 2019 ) also noted that hydrothermal vents are mainly located along the rift axis of the Okinawa Trough. To better understand the ongoing volcanic activities, Tsai et al. ( 2021 ) conducted deep-tow sub-bottom profiler (SBP) and side-scan sonar (SSS) surveys across the entire back-arc basin of the SOT. Their results show that active volcanism in the SOT mainly occurs in the southern half of the back-arc basin. The volcanic activity occurs along several linear or branching zones roughly parallel to the trough axis. On the other hand, the northern half of the back-arc basin exhibits a little volcanic activity but features more brittle normal faults. The areas of active hydrothermal vents display high-temperature and high-pressure fluids expelling into the seawater. These fluids originate from the deep Earth and contain large amounts of minerals and chemicals. This phenomenon significantly impacts geological processes in the sea, such as volcanic activity, sedimentation, and biological ecosystems. These hydrothermal vents often appear in fissures or volcanic areas on the seafloor. The expelled hydrothermal fluids react chemically with the surrounding cold seawater, forming unique geological structures such as black smokers. Additionally, these areas attract biological communities that depend on the chemical energy from hydrothermal vents for survival, including crabs, shrimp, worms, and various microorganisms. The importance of these features in marine environments has been highlighted by Von Damm ( 1990 ), Haymon et al. ( 1993 ), Baker and German ( 2004 ), and Kelley et al. ( 2005 ). To better understand hydrothermal activities, Chen et al. ( 2018 ) and Chou et al. ( 2019 ) employed a Fiber-optical Instrumentation Towed System (FITS) to explore the flat area on the eastern side of the MHV and hilly regions on the southern side. They have identified a near-seafloor temperature anomaly of 0.2°C (from 4.4°C to 4.6°C). They also observed characteristics of hydrothermal seepage in sediment surrounded by biological communities. In contrast, although significant rocky features were found in the uplifted regions of MHV, no biological communities were observed there. Using ROV observations, Chen et al. ( 2023 ) presented two chimney structures emitting hydrothermal flares referred to as the Witch Mound and the Devil Chimney on the eastern side of MHV. Backscatter data obtained from a multi-beam echo sounder (MBES) system showed that these chimneys exhibited high backscatter intensity characteristics. The hydrothermal fluids within the sediments on the east side of MHV were analyzed and showed that the temperature of the hydrothermal fluids in this region likely surpasses 350°C (Hsu et al., 2024 ). The previous results indicate notable features of hydrothermal circulation activities in the MHV region. To provide better acoustic images, we use a deep-tow sonar system to collect side-scan sonar (SSS) and sub-bottom profiler data around the MHV (Fig. 1 c). We aim to comprehensively understand the seabed features of the hydrothermal activity of the MHV. 2. Data collection and processing 2.1 High-resolution deep-tow sonar data The deep-tow sonar data used in this study were collected from three survey cruises. These data were mainly collected using the EdgeTech 2300B deep-tow sonar system. However, Line 11 was collected using the EdgeTech 2400DSS deep-tow sonar system. The 2400DSS deep-tow sonar system operates with SSS frequencies of 120 kHz and 410 kHz, and the chirp frequency range of SBP is 1–10 kHz. The 2300B deep-tow sonar system, on the other hand, has higher SSS frequencies of 230 kHz, 540 kHz, and 850 kHz, and a SBP with a four-transducer array operating within the same frequency range of 1–10 kHz. Compared to the 2400DSS, the 2300B system offers higher-resolution seabed imagery and deeper sediment penetration. The data utilized in this study include both SSS and SBP records. Basic information regarding each survey line, numbered from 01 to 20, is provided in Table 1 . To facilitate data integration and organization, the deep-tow sonar data were renumbered from the east side of MHV to the west (Table 1 and Fig. 1 b). The deep-tow sonar instrument was towed at a speed of ~ 2 knots and deployed at approximately 30 to 50 meters above the seafloor. 2.2 Bathymetry and water column data The bathymetric data of 20-meter resolution in this study area were collected using the Atlas MD50 MBES system (Fig. 1 b) (Tsai et al., 2021 ). During the acquisition of LGD2307 and NOR2-0099 deep-tow sonar and shipborne sub-bottom profiler data, EM122 and EM712 were simultaneously operated along the survey lines. To increase the resolution of the bathymetry in the MHV study area, we conducted a detailed difference analysis on the bathymetric data between the EM122 and the EM712 systems. We compared the beam depths, and the results showed that the depth difference variance ranges from − 5 meters to 10 meters, with an average of + 2.35 meters. The depth values from the EM712 data were corrected based on the average depth difference of + 2.35 meters. Using the EM122 depth distribution as a baseline, we integrated the corrected data from both systems to produce a 5-meter grid resolution seafloor topography map. We employed Globe software (Poncelet et al., 2024 ) to compile the corrected data, generating a high-resolution seafloor topography dataset (Fig. 2 ), the foundational layer for analyzing the MHV area. Echo sounders EM122 and EM712 have also recorded the water column image (WCI) data. Being a deep-sea survey sonar, the EM122 operates at low frequencies (10.5–13.5 kHz) and employs longer pulse lengths, allowing it to probe deep waters but with lower WCI resolution. In contrast, the EM712, with its mid-frequency range (40–100 kHz) and shorter pulse lengths, provides higher WCI resolution. This study utilized the Caris software to process bathymetric data to identify and map hydrothermal vent flares. For example, the water column imagery shown in Fig. 3 a identifies hydrothermal vent flares in the central axis water column profile along the survey line (Fig. 3 b). These identified flares closely match the distribution clusters of hydrothermal vents delineated by Tsai et al. ( 2019 ) using SBES (Fig. 3 a). By examining single WCI cross-sections, this study systematically mapped the distribution and morphological characteristics of the hydrothermal vents, resulting in a detailed hydrothermal vent distribution map and their associated seafloor topography (Fig. 3 c). Interestingly, in the vicinity of the hydrothermal vent clusters east of MHV, an XBT-T5 station X10 recorded a temperature increase of 1.5°C near the seabed, which is atypical compared to other stations (Fig. 3 d). This elevated temperature persisted throughout the recording duration of the XBT (Fig. 3 e), indicating the widespread presence of hydrothermal vents in this area. 3. Seafloor morphology of MHV Morphologically, the MHV is broadly conical. The summit of the volcanic cone is located at a depth of around − 1170 meters, while its base is at approximately − 1350 meters. The volcanic cone has an elevation of about 180 meters and a spatial extent of roughly 2.9 km 2 (Figs. 2 a and 2 b). A prominent depression or a volcanic crater is observed at the summit of MHV (Fig. 2 b). This crater-like feature has a diameter of around 500 meters and a depth of approximately 80 meters, as shown in Profile pp’ of Fig. 2 c. The southern side of the crater was breached, indicating a possible erosion or collapse (Figs. 2 b and 2 c, Profile tt’). The seafloor surrounding MHV displays significant variation of morphology. To the north and south of the volcano's base, within a distance of about 0.5 km, and to the west, within about 1.5 km (the region between the black dashed lines and MHV in Fig. 2 a), the seafloor topography exhibits undulating features. In contrast, the eastern side of MHV is relatively flat. Additionally, the southern bank of MHC has collapsed, as indicated by the red dashed area in Fig. 2 a. The detailed bathymetric survey conducted in this study provides a comprehensive understanding of the MHV's morphology, highlighting its conical shape, crater-like depression, and significant morphological variation in the surrounding area. Submarine volcanoes are usually formed due to magma eruptions resulting from tectonic activity. As magma ascends, it breaks through weak spots in the crust, erupting onto the seabed. The erupted magma cools and solidifies, accumulating into a volcanic cone. Volcanic activity releases significant amounts of heat, gases, and minerals into the ocean, often associated with the formation of hydrothermal deposits (Umbgrove, 1950 ; White, 2005 ; Kase, 2010 ; Costa et al., 2017 ). Tsai et al. ( 2019 ) have identified numerous hydrothermal venting sites around the volcanic structure, primarily located on the eastern and southwestern gentle slopes of the MHV (Fig. 2 a). The XBT station X10 shows a temperature anomaly of approximately 1.5°C (Fig. 3 e) at the seafloor (marked by a star in Fig. 2 a). This study will investigate the causes of seafloor temperature anomalies through deep-tow SSS and SBP analyses. Additionally, it explores why the western side of MHV exhibits large-scale depressed topography and the absence of hydrothermal vents in this area, which instead tend to occur in more gently sloping regions. 4. Hydrothermal circulation characterized by SSS and SBP The detailed SSS images are essential to describe submarine hydrothermal vents. Figure 4 shows the deep-tow SSS observations of hydrothermal vents on the seabed of the MHV area. In contrast to sediments, rocks in SSS images appear as blocks or stripes with varying brightness and texture. These characteristics are mainly due to various rock types' different acoustic impedance properties. High-reflectivity rocks usually show bright areas, while low-reflectivity sediments appear as dark regions (Savini, 2011 ; McMullen et al., 2014; Burguera and Oliver, 2016 ). On the other hand, sediments are loose materials deposited on the seabed and have a density close to seawater, resulting in weaker sonar reflections. In SSS images, sediments are generally represented by flat or undulating terrain with lower reflectivity signals (McMullen et al., 2014). The distinction lies in those sediments, due to their loose structure and lower density, absorb more acoustic energy, resulting in lower backscatter intensity in the images (Savini, 2011 ; Burguera and Oliver, 2016 ). The SSS seabed images in Fig. 4 reveal that apart from regions with significant signal strength fluctuations due to poor instrument dynamics and localized strong backscatter signals in Zone 1 (Fig. 5 a) and Zone 2 (Fig. 6 a), the seabed in the vicinity of MHV predominantly exhibits low backscatter intensity features. This suggests that loose sediments mainly cover the surface of this area. The SBP is a useful tool to understand the shallow subsurface layers of the seabed. It involves acoustic waves (sonar) that penetrate the seabed and reflect off various sediment layers, providing detailed images of the geological structures beneath the seabed. An acoustic transparent zone could reflect hydrothermal vent areas when using a sub-bottom profiler to observe hydrothermal circulation systems. The transparent zones are characterized by the lack of clear reflection from the sediment layers in the seabed. These zones typically correspond to fine-grained sediments or fluid-saturated layers, which have a very low or no acoustic impedance contrast and produce weak or no reflection signals. The formation of transparent zones in sub-bottom profiles in hydrothermal circulation areas are multifaceted and complex. According to Germanovich et al. ( 2011 ), these transparent zones near hydrothermal vents are generally attributed to hydrothermal sediments and the accumulation of biological materials. The intense thermal and chemical activities associated with hydrothermal vents lead to the deposition of minerals such as sulfides, sulfates, and silicates, which can create porous structures that absorb sound energy. These activities influence sediment deposition in the surrounding areas, where fine particles precipitated from hydrothermal flares can settle and form distinct layers in the sediment record. Due to their fine grain size and homogeneous composition, these transparent zones may appear in the substrate profiles (Cann et al., 1997 ). Furthermore, minerals precipitated from hydrothermal fluids, such as sulfides, can form layers with different acoustic properties. If these layers are fine-grained and uniform, they might not strongly reflect sonar waves and thus appear as transparent zones in the sub-bottom profiles (Hannington et al., 1995 ). The thermal and chemical activities associated with hydrothermal vents can alter the surrounding sediments and rocks, potentially changing the physical properties of the materials. If such changes produce more homogeneous and finer-grained materials, they may form transparent zones (Stoffers et al., 1994 ; Johnson and Holmes, 1989 ). Singh et al. ( 2012 ) also noted that accumulating organic matter due to high biological productivity around the vents contributes to forming these transparent zones. In summary, the transparent zones observed in sub-bottom profiles in hydrothermal circulation areas are closely linked to hydrothermal activity, either directly or indirectly. This study focuses on the segment along Line09 where hydrothermal activity was detected (Fig. 7 ; profile location as indicated in Fig. 4 ). The SSS imagery in Fig. 7 a reveals distinct hydrothermal and chimney features on the seabed, along with multiple flare phenomena within the water column. These hydrothermal features observed beneath the SSS instrument correlate well with the stratigraphic characteristics observed in the substrate profile (Fig. 7 b). Figure 7 a shows hydrothermal activity and chimneys are prominently visible on the seabed, and multiple flare phenomena are present in the water column. This image highlights the interaction between the seabed structures and the overlying water column, indicating active hydrothermal discharge zones. The sub-bottom profile results in Fig. 7 b reveal that the shallow strata in this region appear to be influenced by hydrothermal fluids. Additionally, the maximum penetration depth of the sub-bottom profiles in this study is approximately 100 meters. To adequately highlight and differentiate the characteristics of shallow high-resolution strata affected by hydrothermal activity, the strata with no reflective signals are classified into three categories: fluid channels, transparent zones and blanking zones (Fig. 7 b). These fluids migrate upwards through minor normal faults or fractures, cutting through sedimentary layers and forming numerous fluid channels. These channels indicate pathways that allow hydrothermal fluids to ascend towards the seabed. The sub-bottom profile suggests that many fluid channels have merged, creating extensive blanking zones, especially beneath areas with numerous chimney structures (Fig. 7 a). These blanking zones are regions with weak or absent seismic reflection signals, typically caused by fluids that absorb or attenuate the acoustic energy. This phenomenon is commonly associated with hydrothermal areas where fluid saturation disrupts the reflection of sound waves. In regions of the shallow strata that the fluids have not fully penetrated, a substantial transparent zone (TZ) is formed, covered by approximately 5–6 meters of sediment (Fig. 7 b). This transparent zone is characterized by the absence of clear reflection signals, suggesting that it consists of fine-grained, homogeneous materials that do not reflect sonar waves effectively. Even in the strata where some reflection signals can still be detected (Fig. 7 b), there is evidence of fluid intrusion that reduces the impedance contrast between layers. This reduction in impedance contrast decreases the strength of layer reflection signals, indicating ongoing fluid infiltration. The gradual reduction in signal strength within these strata points to the progressive invasion of hydrothermal fluids, altering the physical properties of the layers and diminishing their ability to reflect acoustic waves effectively. By comparing images from SSS and SBP directly beneath, this study identifies the locations of hydrothermal chimneys and flare features (Fig. 7 a) occurring within sedimentary layers where hydrothermal fluids migrate upward (Fig. 7 b). These sections mostly coincide with the distribution of fluid channels, indicating the upward migration of hydrothermal fluids through the overlying sediments. The SBP data shows that sedimentary layers infiltrated by hydrothermal fluids no longer display clear layering information. Additionally, the study finds that while SSS effectively resolves the morphology of chimneys, the corresponding substrate profile exhibits cone-shaped diffraction signals with relatively weaker intensities (Fig. 7 b). This is likely due to the broader beam width of the SBP (the emission angles vary with frequency as follows: about 180° at 1 kHz, 62° at 3 kHz, and 30° at 6 kHz in the SBP mode of the EdgeTech 2300B), compounded by the influence of hydrothermal flares, thereby reducing the clarity of chimney detection. In summary, employing deep-tow sonar systems, this study effectively demonstrates the impact of deep-seated hydrothermal fluid migration on sedimentary layers near the seabed, as evidenced by their reflection characteristics in sub-bottom profiles compared with hydrothermal activity zones observed in SSS imagery. 6. The area of hydrothermal vents Hydrothermal vents typically display point-like or patchy features with strong backscatter intensity in the SSS images (e.g., Fig. 5 b, feature b1, the enlarged figure is located at the top right panel). The backscatter is due to the difference of acoustic impedance between the venting hydrothermal fluids and the surrounding seawater. Figures 5 b, 5 c, and 6 b illustrate three examples of the SSS seabed images of numerous point-like or patchy high-backscatter features. These features indicate hydrothermal seepage areas, providing exact locations of hydrothermal activity on the seabed. Feature c1 (Fig. 5 c, the enlarged figure located at the center right) shows another high-backscatter area at site X10, where a temperature anomaly was observed (Fig. 3 e). Although site X10 does not align with the previously recorded hydrothermal vent locations from the SBES (Fig. 2 ), the new data from the deep-tow SSS confirms that X10 lies within the area of strong backscatter. The studies by Chen et al. ( 2018 ) and Chou et al. ( 2019 ) observed that at locations where near-seafloor temperature increases, there are noticeable hydrothermal flares (Fig. 5 c, feature c2; enlarged view located in the bottom right panel). Hydrothermal fluid leaking into the water column is called hydrothermal flare. In the SSS water column images, flares typically appear as streaks or cloud-like features with a directional spread. This is because the fluid in the flares has a different density than the surrounding seawater, leading to an enhanced scattering signal from the sonar (Baker and German, 2004 ; German and Von Damm, 2006 ; Juniper and Sibuet, 1987 ). Many of these flares were observed in the SSS water column data in Zones 1 and 2, as described in Figs. 5 b, 5 c, and 6 b. Notably, when the towed instrument passes through hydrothermal emission areas, a continuation of the flare structure from the seabed to the water column is observed (Fig. 5 b). The pore water in the MHV hydrothermal field (the core locations for these findings are illustrated in Figs. 5 a and 5 c) has a significant decrease in magnesium ion (Mg²⁺) concentration and a substantial increase in lithium-ion (Li⁺) concentration, indicating the influence of high-temperature hydrothermal fluids (Hsu et al., 2024 ). The hydrothermal fluids in the region may have a temperature exceeding 350°C and could migrate upward through the sediments at a rate of 0.13 to 124 cm/year. Numerous hydrothermal vents have been identified on the south side of the MHV volcanic cone (Zone 3 of Fig. 4 ). These vents are characterized by significant flare features in the water column by the SSS, indicating a high intensity of hydrothermal seepage (Fig. 4 ). The hydrothermal vent images identified by the FITS (Chen et al., 2017; Chou et al., 2019 ) are also located in this area (P mark in Fig. 4 ). It is noted that no active hydrothermal vents had been detected by SBES in the western side of the MHV water column data (Fig. 2 ). However, this study's SSS images show two potential hydrothermal seepages in Zone 4 (Fig. 4 ), with flare characteristics indicating the presence of weak hydrothermal leakage (Fig. 4 ). Compared to Zone 1, Zone 2 and Zone 3, the seepage intensity in Zone 4 appears significantly weaker. This highlights that shipborne sonar systems cannot easily detect hydrothermal vents with lower intensity. 6.1 Seafloor features of hydrothermal chimneys Hydrothermal chimneys are conduits in hydrothermal circulation systems. Metal-sulfide-rich hydrothermal fluids are expelled through the chimneys. Vertical or inclined rod-like or conical features typically characterize these chimneys. Our study identified numerous black smoker features correlated to hydrothermal vents on the seabed imagery from the eastern side of MHV, specifically within Zone 1 (Fig. 5 a). According to the seabed imagery examples (Figs. 5 b and 5 c), black smokers in this area are predominantly distributed within regions marked by point-like or patchy high-backscatter signals indicative of hydrothermal vents. These black smokers usually exist in clusters. The variations in signal strength and shadow lengths in the SSS imagery suggest these black smokers have a rough appearance. When the towed SSS instrument passes directly over a black smoker, hydrothermal flares emitting into the water column can be observed (Fig. 5 b, feature b1). The black smoker Devil Chimney (Chen et al., 2023 ), is situated within the black smoker group in Zone 1, as shown in Figs. 5 a and 5 b (marked as D). Another black smoker, Witch Mound (Chen et al., 2023 ), has high-backscatter signals and hydrothermal venting but seems not to have developed into a fully formed black smoker yet (marked as W in Fig. 5 a, bottom right). The hydrothermal vent areas located west and south of MHV (Zone 2 in Fig. 4 ) present distinct characteristics of SSS seabed imagery (Fig. 6 a). The chimneys display individual mounds (Fig. 6 b). This area shows hydrothermal vents with limited distribution, characterized by point-like or patchy high-backscatter signals, but with generally lower backscatter intensity compared to the chimneys in Zone 1 (Fig. 5 b). The SSS imagery indicates that the seabed in Zone 2 is heavily covered with sediments. The chimney structures are individual mounds and do not display prominent seabed features. It is hypothesized that the hydrothermal fluids may mix with cold seawater within the sediment layer, causing the metals to precipitate as sulfides within the substratum. This process could form white smokers or diffuse flows where the fluids percolate through the seabed without forming distinct chimneys. In the hydrothermal vent area at the southern base of MHV (Zone 3 in Fig. 4 ), SSS seabed imagery reveals point-like or patchy high-backscatter signals and linear features (Fig. 4 , top right inset). However, when these sonar features are overlaid with seabed topography (Fig. 4 ), the SSS characteristics of Zone 3 primarily reflect the topographic variations rather than active black smoker structures. The hydrothermal activity in this region is likely due to fluids seeping through fractures in the near-seabed volcanic terrain of MHV. Additionally, the hydrothermal seepage areas in Zone 4 (Fig. 4 , bottom right inset) primarily reflect seabed topographic variations. No significant chimney structures have been detected in these zones, suggesting that the hydrothermal fluids might seep diffusely through the seabed without forming notable chimney features. Based on observations from the deep-tow SSS images, the hydrothermal circulation at the MHV is currently active on its eastern side, particularly in Zone 1 (Fig. 4 ). This area is characterized by considerable hydrothermal discharge and abundant black smoker structures. The seabed in this zone contains hydrothermal vents and chimney formations, indicating ongoing and vigorous hydrothermal activity. In contrast, the southwest area (Zone 2 in Fig. 4 ) and the southern volcanic cone of MHV (Zone 3 in Fig. 4 ) exhibit only localized hydrothermal activity. The hydrothermal discharge in these areas is limited, with smaller venting zones and less defined chimney structures. The SSS imagery in these regions shows hydrothermal emissions are more sporadic and less intense than in Zone 1. The limited and diffuse nature of the hydrothermal activity in Zones 2 and 3 suggests that these areas are farther from the primary hydrothermal circulation system. 6.2 Shallow strata features of hydrothermal chimneys We collected 20 deep-tow sub-bottom profiler and SSS data (Fig. 1 and Table 1 ). Here, we focus on the influence of hydrothermal activity on the shallow substrata in the MHV region. One profile crossing the central MHV body and three profiles on the eastern side are particularly shown here (Figs. 8 – 11 ; Table 1 ). The analysis elucidates the impact on shallow substrata in the presence of hydrothermal activity and chimney features in the MHV area. (a) Sub-bottom profile Line13 This profile is located on the western side of MHV and represents the closest line to the MHV summit (Fig. 1 b). From northeast to southwest, this profile shows characteristics of fluid channels and fractured geological layers between 8.5 and 8 km near the southern embankment of MHC (Fig. 8 a). The seabed exhibits significant undulations toward 8-3.5 km. It is partly covered by ~ 5 m thick sediment, and a pronounced blanking zone is observed beneath the sediment layers, which are indistinguishable (Fig. 8 a). Between 3.5 and 2.5 km, sediment layers are interrupted by large-scale fluid channels, cutting through two transparent zones (TZ-1 and TZ-2, as labelled in this study). There is a ~ 5 m thick layer of sediment in the seabed where TZ-1 exist. At 3.5 km, the seabed topography changes from steep undulation on the northeast to a gentle slope on the southwest, coinciding with the occurrence of hydrothermal venting in the water column located in the transition zone of this topographic change (Fig. 8 c; profile position within the cyan dashed box area in Fig. 8 b). Additionally, between 4 and 3 km, cone-shaped geological features of possible chimneys are observed. Comparison with the corresponding SSS data shows similar protrusions in both seabed and water column images (Fig. 8 c), though these chimney features are less distinct than those in Fig. 8 . TZ-1 is separated at ~ 1.5 km, and the geological layers on both sides show significant tilting, especially with a larger tilt angle on the northeast side (Fig. 8 d). Below this area, characteristics such as normal faults, fractures, and small-scale fluid channels are observed in the underlying layers. Within the distance between 1.5 and 0 km, the transparent zone TZ-3 is identified beneath a sediment layer of ~ 30–40 m thick. Unlike the transparent zone near the seabed on the northeast side, TZ-3 retains identifiable layer sequences, with deposition patterns and tilt angles nearly identical to the sediment layers above and below it (Fig. 8 e). (b) Sub-bottom profile Line20 This profile represents the westernmost sub-bottom profile collected in MHV as part of this project (Fig. 1 b), where no intense seabed topographic features were observed. There are also no blanking zones indicating completely indiscernible stratigraphic sequences in the subsurface (Fig. 9 a). Instead, within the distance between 10 and 7.5 km, the clear acoustic transparent zone TZ-1 exists, together with numerous fluid channels intersecting and penetrating the strata (Fig. 9 a). The TZ-1 layer is overlain by ~ 5 meters of modern sediment, but the SSS seabed and water column images in the region did not reveal any chimneys or hydrothermal flare features (Fig. 9 c; delineated by the cyan dashed box in Fig. 9 b). Towards the southwest, at ~ 5.5 km distance, three acoustic transparent zones (TZ-3, TZ-4, and TZ-5) are found. According to the subsidence or uplift reference line on this profile, the seafloor elevation within this area indicates a maximum change of approximately 60–70 m. (c) Sub-bottom profile Line08 This profile is located near the center of a hydrothermal vent on the eastern side of the MHV (Fig. 1 b). Compared to Line13 (Fig. 8 ), in the segment between 6.2 and 4.2 km of the hydrothermal activity, no blanking zones is observed (Fig. 9 ). Instead, there are fluid channel features intersecting and penetrating through the strata (Fig. 10 ). However, unlike Line20, the seabed of Line08 exhibits a feature of abundant hydrothermal vents and chimneys in the SSS imagery (Fig. 10 c, delineated by the cyan dashed box in Fig. 10 b). These features also appear in the sub-bottom profile. This indicates that the 6.2–4.2 km segment of the Line08 represents a main location where hydrothermal fluids occur in the seabed. The hydrothermal activity is vigorous, suggesting this region is in a mature stage of hydrothermal activity. The most significant difference between Line08 and other profiles on the eastern side of MHV is TZ-1 layer connects directly with the main hydrothermal body at the distance of ~ 4.2 km. The TZ-1 layer here is thinner compared to profiles on the western side of MHV (Fig. 8 and Fig. 9 ). There is no subsidence evidence in the layers beneath TZ-1. Instead, they are overlaid by ~ 5 meters thick sediment (Fig. 10 d). Besides TZ-1, the Line08 sub-bottom profile also show TZ-2 and TZ-6 acoustic transparent zones (Fig. 10 a). According to the reference line of subsidence or uplift in this section, changes in seafloor elevation near the hydrothermal activity area show a maximum downward movement of about 10–20 meters. This indicates that hydrothermal fluid flow can significantly influence dynamics of the strata. (f) Sub-bottom profile Line02 This profile is located exactly at the eastern boundary of hydrothermal vent activity on the seabed of MHV (Fig. 1 b). Compared to Line13 (Fig. 8 ), sub-bottom profile Line02 contains hydrothermal fluids which gradually ascend into the strata (Fig. 11 a). At the distance of 5 km, a small-scale hydrothermal flare is shown in the SSS imagery (Fig. 11 c; delineated by the cyan box in Fig. 11 b). Unlike other profiles, acoustic transparent zone TZ-1 is developed. However, at approximately 30–40 meters below the seabed, the sub-bottom profile show TZ-2 previously intersected by fluid channels, and TZ-6 located at 70–80 meters below the seabed (Fig. 11 d). The sedimentary layers and geological trends observed in Line02 indicate a southwestward dipping structure (Fig. 11 a) consistent with the topography. All these observations suggest that this region is in a developing stage of hydrothermal activity. Additionally, although hydrothermal activity has not completely occupied the shallow seabed on this profile, there is already a seafloor variation of ~ 5–10 meters in the central hydrothermal activity zone (Fig. 11 a). This demonstrates that within the central hydrothermal activity zones, ongoing intrusion of hydrothermal fluids continues to affect the shallower layers. 7. Integrated interpretation of the MHV morphology Here shows the interpretation from 20 northeast-southwest oriented deep-tow sub-bottom profiles and one shipboard sub-bottom profile from west to east (Figs. 12 a- 12 d; profile locations as shown in Fig. 1 b; profile information as shown in Table 1 ). Figures 12 a and 12 b are located on the west side of MHV, while Figs. 12 c and 12 d are on the east side of MHV. Additionally, the study includes results from 5 northwest-southeast oriented shipboard sub-bottom profiles (Fig. 12 e; profile locations are shown in Fig. 1 b; profile information is shown in Table 1 ). Based on 26 sub-bottom profiles, we could better understand the different geological features related to the hydrothermal activity in the seabed of the MHV region. The interpretations are as follows: Comparison with SSS seabed and water column hydrothermal features reveals that the blanking zones and transparent zone in the seabed of the MHV region are geological features caused by hydrothermal activity. As deep-seated hydrothermal activity migrates upwards through minor normal faults or fractures to form fluid channels, several transparent zones can sequentially develop. In this study, the shallowest transparent zone in the MHV area is marked as Transparent Zone-1 (TZ-1) (Fig. 12 ). As deep-seated hydrothermal activity migrates upwards and diffuse outward, these transparent zones gradually connect with the main conduit of the hydrothermal activity (see Lines 01–09 in Figs. 12 c-d). If the deep hydrothermal fluids continue to migrate upward, they will eventually penetrate the sedimentary layers, forming a blanking zone (as observed in Lines 10–17 in Figs. 12 a-c). However, suppose the upward migration of deep hydrothermal fluids stop, the layers beneath the transparent zone will not be completely invaded by the hydrothermal fluids, resulting in a geological feature where fluid channels coexist with sedimentary layers without forming a blanking zone (as observed in Lines 18–20 in Fig. 12 a). This scenario illustrates that the migration activity of deep-seated hydrothermal fluids can vary with the change in spatiotemporal conditions and affect the hydrothermal activity features near the seafloor. In the area where the TZ-1 is distributed, the strata incline towards the summit of the MHV (as seen in Lines 10–20 in Figs. 12 a-c). Besides, the integrated sub-bottom profile diagram reveals that the overall topographic gradient slopes from the northeast to the southwest. The strata beneath both flanks of the TZ-1 incline towards the blanking zone. This study indicate that the strata affected by hydrothermal activity display gradual subsidence, forming minor normal faults or fractures, creating new fluid channels, and allowing hydrothermal activity to spread around the MHV gradually. The large-scale, rugged topographic features observed on the morphology of the MHV area (Fig. 2 ) are almost located within the distribution range of the blanking zone in the sub-bottom profiles (Lines 10–17 in Figs. 12 a-c). Significant morphological undulations are also observed in most active areas of hydrothermal activity, such as the region between Lines 07 and 09 (Fig. 12 c). The persistent influence of hydrothermal intrusions has caused gradual subsidence and weakening of the sedimentary layers around MHV. Finally, large-scale mass collapse may occur because of the inability to withstand the overlying gravity. The collapsed MHC escarpment, located northeast of MHV (Fig. 2 ), could be associated with the hydrothermal activity as evidenced by the distribution of TZ-1 and fluid channels in the sub-bottom profiles between Lines 11–14 in Fig. 12 b. Since the MHV consists of igneous rocks, it maintains its high topographic feature. The hydrothermal activity has weakened the seabed of the western and southern sides of MHV. The TZ-1 is overlain by about 5 meters sediments, which constrain the formation of chimney-like structures (Line13 and Line17 in Fig. 12 a and Fig. 12 b). Therefore, almost no chimney structures are found in the seabed in the western and southern sides of MHV. In the eastern side of the MHV, numerous chimney-like features are observed (e.g. Lines 8–10 of Figs. 12 c and 12 d). The subsurface layers in this region show that deep-seated hydrothermal fluids have migrated upwards through fluid channels, near the seafloor. The deep hydrothermal activity in the MHV region is active now in the eastern side. Because of the upward migration and infiltration of these hydrothermal fluids into surrounding strata, hydrothermal processes are developing eastward (e.g. Line07 to Line02 in Figs. 12 c and 12 d). Line01 in Fig. 12 d demonstrates that the deep hydrothermal activity is at ~ 20–30 meters below the seafloor. It is inferred that the current hydrothermal activity in the eastern side of the MHV is active in the area between Line01 and Line02 (Fig. 12 d). The distribution of TZ-1 (from Lines 4 to 26 in Fig. 12 ) indicates that the sediment subsidence area is mainly due to hydrothermal activity. These areas probably consist of the recent deposition of hydrothermal minerals in the MHV region. Based on the sub-bottom profiles in Fig. 12 , the boundary of the TZ-1 distribution is delineated. 8. Discussion 8.1 Relationship between Hydrothermal Activity and Seabed Structures This study illustrates the interpretation of relevant features of hydrothermal activity in the MHV region, including hydrothermal vent distribution analyzed by chartered shipborne sonar and SSS water column imaging, as well as subsurface acoustic transparent zones, fluid channels, chimney structures, small normal faults, and fractures. Those features are superposed onto seabed topography and slope maps (Fig. 13 ). The results indicate that the hydrothermal activity in the MHV has occurred in its eastern and southwestern margins (Fig. 13 a). The eastern region is the primary zone of hydrothermal activity, where numerous and widely distributed hydrothermal vents and distinct chimney structures exist in the seabed (Fig. 13 a). In contrast, there are fewer hydrothermal activity features on the southwestern boundary (Fig. 13 a). In addition, based on the interpretation of the upper boundary of TZ-1 from sub-bottom profiles within the region, we can define the boundary of sediment subsidence in the near-seabed of the MHV (Fig. 13 b). The distribution of minor normal faults or fractures near the seabed predominantly exists along the boundary of sediment subsidence (Fig. 13 b). Furthermore, the distribution of fluid channels within the boundary of sediment subsidence makes it evident that regions with greater slope variations almost lack the presence of fluid channels (Fig. 13 b). This suggests that the areas with the most significant terrain variations in and around MHV are closely related to the distribution zone of blanking zones observed in sub-bottom profiles (Fig. 12 ). Through this analysis, the extent of collapses induced by hydrothermal activity in the near-seabed sediment layers of MHV is estimated to be an area of approximately 14 km² (Fig. 13 b). Additionally, using the southern dike of MHC on the northeast side of MHV as a natural boundary for near-seafloor hydrothermal activity within the study area, the sediment subsidence area between the boundary of subsidence and collapse is estimated to cover approximately 16 km². Based on the analysis in Fig. 13 , this study proposes that the region within the boundary of collapse is likely the earliest hydrothermal activity zone in the MHV. As deep-seated hydrothermal fluids migrated upwards and invaded surrounding sedimentary layers, the lower sedimentary layers gradually subsided. Eventually, if the upper layers cannot be sustained, significant collapses occur. The area between the boundary of collapse and subsidence is characterized by the formation of minor normal faults or fractures that were initially formed. These features intersect sedimentary layers, creating fluid channels that gradually spread outward, leading to slow subsidence of sedimentary layers. New minor normal faults or fracture systems are developing near the subsidence boundary. On the eastern side of MHV, sub-bottom profiles show the features of upward hydrothermal migration (Line01 in Fig. 12 d). Based on the characteristics and the boundary of the seabed hydrothermal activities, this study suggests that the area of the potential hydrothermal mineral deposits in MHV is approximately 30 km², located within the limit of sediment subsidence zones. Hydrothermal mineral deposits are likely found in the seabed of the eastern side of MHV because of intense hydrothermal activity. 8.2. Distribution of Recent Seabed Hydrothermal Activity in the MHV Region A comprehensive SSS image analysis shows hydrothermal vent activities are found in both the seabed and water column. Chimney structures observed in seabed profiles allow the identification of numerous seabed areas with hydrothermal potential (Fig. 14 ). Notably, the areas with chimney structures have been identified (marked with cyan stars in Fig. 14 ) on the eastern side of MHV (Fig. 14 ). These current seabed hydrothermal potential areas are distributed along the boundary of collapse zones (Fig. 14 ). This implies that after the collapse of the near-seabed layers, the migration path of the hydrothermal fluids is towards the seabed surface. The deep-seated hydrothermal fluid flows to seep out and weaken areas in terms of minor normal faults or fractures. Additionally, considering MHV as a center, it can be observed that the distribution width of the blanking zone in seabed profiles is more comprehensive to the west and narrower to the east. Similarly, the distribution width and thickness of the TZ-1 also exhibit a broader and thicker structure to the west and a narrower and thinner one to the east (Fig. 12 ). Based on this, the early-stage hydrothermal activity on the seabed initially could develop towards the western side of MHV. As continuous hydrothermal activity-induced changes in the geological layers, the upward migration of deep-seated hydrothermal fluids gradually shifted towards the current eastern side of MHV. 9. Conclusion Hydrothermal activity has significantly developed in the MHV area. The sub-bottom profiler data can reveal acoustic transparent zones related to high-porosity sedimentary layers intruded by deep hydrothermal fluids. When the deep hydrothermal fluids have migrated upwards and diffused into surrounding strata, the shallow layers become gradually homogeneous and indistinguishable in the sub-bottom profiler data. Six transparent zones are identified in the sub-bottom profiles in the MHV area. The shallowest one in the seabed is labelled as TZ-1. In the area where the TZ-1 exists, the strata tend to tilt toward the summit of the MHV. The strata affected by hydrothermal fluid activity display gradual subsidence. This process could create minor normal faults or fractures, providing hydrothermal fluid channels to spread around the MHV. In regions where the blanking zone exists, the terrain shows morphological undulation due to the progressive weakening of the strata. Finally, large-scale sedimentary layer collapses occur. One collapse has caused the missing segment of the MHC dam in the northeast side of MHV. Hydrothermal activity in the western MHV has significantly decreased; no hydrothermal gas flare is found. In contrast, the SSS images and sub-bottom profiler data show numerous active hydrothermal vents and seabed chimney features in the eastern MHV. It suggests that the seabed hydrothermal activity is now active in the eastern side of the MHV. The east boundary of the hydrothermal fluid activity in the MHV region is between Line01 and Line02. Due to past hydrothermal activity, the western and southern sides of the MHV have experienced significant sedimentary subsidence or large-scale collapses. The collapse or subsidence of strata can be a signal indicating a decrease of hydrothermal activity. Based on the analysis of bathymetric slope variations and the distribution of the TZ-1, blanking zone and fluid channels, we have identified the outline of the seabed collapses surrounding the MHV. The estimated area of the seabed collapses is approximately 14 km 2 . The strata collapse and subsidence are characteristic of the seabed influenced by hydrothermal activities. We estimate that the area of potential hydrothermal mineral deposits in the MHV seabed is approximately 30 km 2 . Declarations Author Contribution Ching-Hui Tsai, Shu-Kun Hsu, and Hsiao-Shan Lin were responsible for data processing, figure creation, and writing the manuscript.Song-Chuen Chen, Liwen Chen, Ching Hsu, and Lien-Kai Lin participated in discussions and provided suggestions.Chin-Wei Liang and Yen-Yu Cho assisted with data collection. Acknowledgement This study was mainly supported by the Geological Survey and Mining Management Agency (GSMMA), the Ministry of Economic Affairs (MOEA), and the National Science and Technology Council, Taiwan. Part support was from the National Academy of Marine Research (NAMR) of the Ocean Affairs Council (OAC), Taiwan. We extend our gratitude to the crew of the R/V Legend, R/V Ocean Researcher I (OR1), and R/V New Ocean Researcher 2 (NOR2) for their invaluable assistance in data collection. References Baker, E. T., & German, C. R. (2004). On the global distribution of hydrothermal vent fields. In Mid-Ocean Ridges: Hydrothermal Interactions Between the Lithosphere and Oceans (pp. 245-266). American Geophysical Union. Burguera, A., & Oliver, G. (2016). High-Resolution Underwater Mapping Using Side-Scan Sonar. PLOS ONE, 11(1), e0146396. https://doi.org/10.1371/journal.pone.0146396 Butterfield, D. A., McDuff, R. E., Lilley, M. D., Lupton, J. E., & Massoth, G. J. (1994). Geochemistry of hydrothermal fluids from Axial Seamount hydrothermal emissions study vent field, Juan de Fuca Ridge: subseafloor boiling and subsequent fluid-rock interaction. Journal of Geophysical Research: Solid Earth, 99(B5), 9561-9594. Cann, J. R., Blackman, D. K., Smith, D. K., McAllister, E., Janssen, B., Mello, S., Pascoe, A. R., Avgerinos, E., & Escartin, J. (1997). Corrugated slip surfaces formed at North Atlantic ridge-transform intersections. Nature, 385(6614), 329-332. Chen, H. H., Chou, Y. C., Wang, C. C., Lin, Y. H., Lin, J. M., Liao, Y. C., Chen, S. C., Wei, C. Y., Chen, J. E., & Wang, Y. (2018). Seafloor Surveys using Deep-towed Vehicles for Mineral Resource Investigation off Taiwan.Paper presented at the OCEANS 2018 MTS/IEEE Charleston. Chen, T. T., Hsu, H. H., Su, C. C., Liu, C. S., Wang, Y., Chen, S. C., & Wu, S. F. (2023). Hydrothermal characteristics of the Mienhua submarine volcano in the southernmost Okinawa trough. Marine Geophysical Research, 44(2), 10. Chou, Y. C., Wang, C. C., Chen, H. H., & Lin, Y. H. (2019). Seafloor characterization in the southernmost Okinawa Trough from underwater optical imagery. Terrestrial, Atmospheric & Oceanic Sciences, 30(5). Costa, P. M., Escartín, J., Tivey, M. A., Lin, J., & German, C. R. (2017). Submarine Volcanoes and Hydrothermal Systems. Geological Society Special Publication. Edmond, J. M., Measures, C., McDuff, R. E., Chan, L. H., Collier, R., Grant, B., Gordon, J. B., & Corliss, J. B. (1979). Ridge crest hydrothermal activity and the balances of the major and minor elements in the ocean: the Galapagos data. Earth and Planetary Science Letters, 46(1), 1-18. Fabbri, O., Monié, P., & Fournier, M. (2004). Transtensional deformation at the junction between the Okinawa trough back-arc basin and the SW Japan island arc. Geological Society of London Special Publication, 227(1), 297-312. German, C. R., & Von Damm, K. L. (2006). Hydrothermal processes. In Treatise on Geochemistry, 6, 181-222. Germanovich, L. N., Ballu, V., & Bouguet, C. (2011). Geophysical and Hydrothermal Signatures of Submarine Vent Fields. Geophysical Research Letters, 38, L15302. doi:10.1029/2011GL048337. Gungor, A., Lee, G. H., Kim, H. J., Han, H. C., Kang, M. H., Kim, J., & Sunwoo, D. (2012). Structural characteristics of the northern Okinawa Trough and adjacent areas from regional seismic reflection data: geologic and tectonic implications. Tectonophysics, 522, 198-207. Hannington, M. D., Jonasson, I. R., Herzig, P. M., & Petersen, S. (1995). Physical and chemical processes of seafloor mineralization at mid-ocean ridges. Reviews of Geophysics, 33(2), 109-135. Haymon, R., Fornari, D., Von Damm, K. L., Lilley, M., Perfit, M., Edmond, J., Shanks III, W. C., Lutz, R., Grebmeier, J., Carbotte, S. J. E., & Letters, P. S (1993). Volcanic eruption of the mid-ocean ridge along the East Pacific Rise crest at 9°45–52’N: direct submersible observations of seafloor phenomena associated with an eruption event in April 1991. Earth and Planetary Science Letters, 119(1-2), 85-101. Hsu, F. H., Su, C. C., Lin, Y. S., Lee, H. F., Chu, M. F., Lan, T., Wu, S.-F., & Chen, S. C. (2024). Geochemical indications of hydrothermal fluid through sediments within the Geolin Mounds and Mienhua Volcano hydrothermal fields, southernmost Okinawa Trough. Deep Sea Research Part I: Oceanographic Research Papers, 207, 104293. Hsu, S. K., 2001. Lithospheric structure, buoyancy and coupling across the southernmost Ryukyu subduction zone: An example of decreasing plate coupling. Earth Planet. Sci. Lett., 186, 471-478. Hsu, S. K., Yeh, Y. C., Sibuet, J. C., Doo, W. B., & Tsai, C. H. (2013). A mega-splay fault system and tsunami hazard in the southern Ryukyu subduction zone. Earth and Planetary Science Letters, 362, 99–107. Ifremer, Shom (2022). DORIS Software. SEANOE. https://doi.org/10.17882/90121 Johnson, H. P., & Holmes, M. L. (1989). Evolution and hydrothermal activity of the Juan de Fuca Ridge. Journal of Geophysical Research: Solid Earth, 94(B12), 15777-15792. Juniper, S. K., & Sibuet, M. (1987). Vent fauna on an Eiffel Tower hydrothermal edifice on the Juan de Fuca Ridge. Marine Ecology Progress Series, 40, 65-73. Kase, M. (2010). Submarine Volcanism and Associated Hydrothermal Activity and Mineral Deposits. Tokyo University Press. Kelley, D. S., Karson, J. A., Früh-Green, G. L., Yoerger, D. R., Shank, T. M., Butterfield, D. A., Hayes, J. M., Schrenk, M. O., Olson, E. J., Proskurowski, G., Jakuba, M., Bradley, A., Larson, B., Ludwig, K., Glickson, D., Buckman, K., Bradley, A. S., Brazelton, W. J., Roe, K., Elend, M. J., Delacour, A., Bernasconi, S. M., Lilley, M. D., Baross, J. A., Summons, R. E., & Sylva, S. P. (2005). A serpentinite-hosted ecosystem: the Lost City hydrothermal field. Science, 307(5714), 1428-1434. Kimura, M. (1985). Back-arc rifting in the Okinawa Trough. Marine and Petroleum Geology, 2(3), 222–240. Kodaira, S., Iwasaki, T., Urabe, T., Kanazawa, T., Egloff, F., Makris, J., & Shimamura, H. (1996). Crustal structure across the middle Ryukyu trench obtained from ocean bottom seismographic data. Tectonophysics, 263(1-4), 39–60. Lee, C. S., Shor, G. G., Bibee, L. D., Lu, R. S., & Hilde, T. (1980). Okinawa Trough: Origin of a back-arc basin. Marine Geology, 35, 219–241. Letouzey, J., & Kimura, M. (1986). The Okinawa Trough: genesis of a back-arc basin developing along a continental margin. Tectonophysics, 125(1–3), 209–230. Lin, Y. C., Lin, J. Y., Hsu, S. K., Chen, S. C., Lin, S. S., & Tsai, C. H. (2024). Gas emission characteristics and tectonic implications in the southernmost Okinawa Trough from split‐beam echo sounder observations. Journal of Geophysical Research: Oceans, 129(3), e2023JC020176. Massoth, G. J., Milburn, H. B., Hammond, S. R., Butterfield, D. A., McDuff, R. E., & Lupton, J. E. (1988). The geochemistry of submarine venting fluids at Axial Volcano, Juan de Fuca Ridge: New sampling methods and a VENTS program rationale. In Global venting, midwater, and benthic ecological processes (Vol. 84, pp. 29-59). NOAA Rockville, MD. McMullen, K. Y., Poppe, L. J., Ackerman, S. D., Blackwood, D. S., Lewit, P. G., & Parker, C. E. (2013). Sea-Floor Geology in Northeastern Block Island Sound, Rhode Island (No. 2013-1003). US Geological Survey. Morton, B. R., Taylor, G. I., & Turner, J. S. (1956). Turbulent gravitational convection from maintained and instantaneous sources. Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, 234(1196), 1-23. Poncelet, C., Billant, G., Corre, M.-P., & Saunier, A. (2024). Globe (GLobal Oceanographic Bathymetry Explorer) Software. SEANOE. https://doi.org/10.17882/70460 Savini, A. (2011). Side-Scan Sonar as a Tool for Seafloor Imagery: Examples from the Mediterranean Continental Margin. In Sonar Systems. InTech. http://dx.doi.org/10.5772/18375 Shinjo, R., Chung, S. L., Kato, Y., & Kimura, M. (1999). Geochemical and Sr-Nd isotopic characteristics of volcanic rocks from the Okinawa Trough and Ryukyu Arc: implications for the evolution of a young, intracontinental back arc basin. Journal of Geophysical Research: Solid Earth, 104, 10591–10608. Sibuet, J. C., Deffontaines, B., Hsu, S.-K., Thareau, N., LeFormal, J. P., Liu, C.-H., & Party, A. (1998). Okinawa Trough backarc basin: early tectonic and magmatic evolution. Journal of Geophysical Research: Solid Earth, 103, 30245–30267. Sibuet, J. C., Hsu, S. K., Shyu, C. T., & Liu, C. S. (1995). Structural and kinematic evolutions of the Okinawa Trough backarc basin. Backarc basins: Tectonics and magmatism, 343-379. Sibuet, J. C., Letouzey, J., Barrier, F., Charvet, J., Foucher, J. P., Hilde, T. W. C., Kimura, M., Chiao, L.-Y., Marsset, B., Muller, C., & Stephan, J. F. (1987). Back arc extension in the Okinawa trough. Journal of Geophysical Research, 92, 14041–14063. Singh, H., Shank, T., & Fornari, D. (2012). Hydrothermal Vent Geomorphology and the Influence of Geological Processes on Vent Communities. Oceanography, 25(1), 44-53. doi:10.5670/oceanog.2012.15. Sinquin, J. M., Lurton, X., Vrignaud, C., Mathieu, G., & Bisquay, H. (2016). DORIS Software: New Tool to Process Sound Velocity Profiles. Hydro International, 20, 22-25. Stoffers, P., Worthington, T. J., Hekinian, R., & Shipboard Scientific Party (1994). Hydrothermal activity and its influence on sedimentation in the Manus Basin. Marine Geology, 116(1-2), 51-82. Tivey, M. K., Humphris, S. E., Thompson, G., Hannington, M. D., & Rona, P. A. (1995). Deducing patterns of fluid flow and mixing within the TAG active hydrothermal mound using mineralogical and geochemical data. Journal of Geophysical Research: Solid Earth, 100(B7), 12527-12555. Tsai, C. H., Hsu, S. K., Chen, Y. F., Lin, H. S., Wang, S. Y., Chen, S. C., & Cho, Y. Y. (2019). Gas plumes and near-seafloor bottom current speeds of the southernmost Okinawa Trough were determined by echo sounders. Terrestrial, Atmospheric & Oceanic Sciences, 30(5). Tsai, C. H., Hsu, S. K., Chen, S. C., Wang, S. Y., Lin, L. K., Huang, P. C., Chen, K. T., Lin, H. S., Liang, C. W., & Cho, Y. Y. (2021). Active tectonics and volcanism in the southernmost Okinawa Trough back-arc basin derived from deep-towed sonar surveys. Tectonophysics, 817, 229047. https://doi.org/10.1016/j.tecto.2021.229047. Tunnicliffe, V., Juniper, S. K., & Sibuet, M. (2003). Reducing environments of the deep-sea floor. Oceanography and Marine Biology: An Annual Review, 41, 1-44. Umbgrove, J. H. F. (1950). Studies on Submarine Volcanoes. Springer. Von Damm, K. L. (1990). Seafloor hydrothermal activity: black smoker chemistry and chimneys. Annual Review of Earth and Planetary Sciences, 18(1), 173-204. White, R. S. (2005). Submarine Volcanism and Hydrothermal Activity. Marine Geology. 215(1-2), 7-20. Tables Tables 1 and 2 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Table01.png Table 1. Summary of Survey Line Information in This Study. The table below provides detailed information about the survey lines, including the SSS and SBP data collection instruments and their respective frequencies. Table02.png Table 2. Distribution of Recent Sediment Thickness Above Transparent Zone-1 (TZ-1) in Subsurface Profiles Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 17 Oct, 2024 Reviews received at journal 17 Oct, 2024 Reviews received at journal 07 Oct, 2024 Reviewers agreed at journal 15 Sep, 2024 Reviewers agreed at journal 14 Sep, 2024 Reviewers invited by journal 14 Sep, 2024 Editor assigned by journal 14 Aug, 2024 Submission checks completed at journal 14 Aug, 2024 First submitted to journal 14 Aug, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4913834","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":343952575,"identity":"7b296840-1105-44eb-a801-9b60a0d2934b","order_by":0,"name":"Ching-Hui Tsai","email":"data:image/png;base64,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","orcid":"","institution":"National Central University","correspondingAuthor":true,"prefix":"","firstName":"Ching-Hui","middleName":"","lastName":"Tsai","suffix":""},{"id":343952576,"identity":"aa773bae-f87f-4780-bbb5-232d461b51cb","order_by":1,"name":"Shu-Kun Hsu","email":"","orcid":"","institution":"National Central University","correspondingAuthor":false,"prefix":"","firstName":"Shu-Kun","middleName":"","lastName":"Hsu","suffix":""},{"id":343952578,"identity":"9bc1fe6c-2678-4a03-9c99-1eff9eca81b3","order_by":2,"name":"Hsiao-Shan Lin","email":"","orcid":"","institution":"National Central University","correspondingAuthor":false,"prefix":"","firstName":"Hsiao-Shan","middleName":"","lastName":"Lin","suffix":""},{"id":343952579,"identity":"69d200a2-6249-4541-a043-5c22d6ecb5be","order_by":3,"name":"Song-Chuen Chen","email":"","orcid":"","institution":"Ministry of Economic Affairs","correspondingAuthor":false,"prefix":"","firstName":"Song-Chuen","middleName":"","lastName":"Chen","suffix":""},{"id":343952580,"identity":"a00d03bc-be61-47fe-afd3-27817e311150","order_by":4,"name":"Liwen Chen","email":"","orcid":"","institution":"National Academy of Marine Research, Ocean Affairs Council","correspondingAuthor":false,"prefix":"","firstName":"Liwen","middleName":"","lastName":"Chen","suffix":""},{"id":343952581,"identity":"16a9b43f-d7bd-423b-a142-3fad912e6b1a","order_by":5,"name":"Chin-Wei Liang","email":"","orcid":"","institution":"National Central University","correspondingAuthor":false,"prefix":"","firstName":"Chin-Wei","middleName":"","lastName":"Liang","suffix":""},{"id":343952582,"identity":"3e78cf83-f271-4204-8eb8-29e0df14760e","order_by":6,"name":"Ching Hsu","email":"","orcid":"","institution":"National Central University","correspondingAuthor":false,"prefix":"","firstName":"Ching","middleName":"","lastName":"Hsu","suffix":""},{"id":343952583,"identity":"9f2ed9cb-3ec6-46ee-8123-36b0b18619fe","order_by":7,"name":"Lien-Kai Lin","email":"","orcid":"","institution":"National Central University","correspondingAuthor":false,"prefix":"","firstName":"Lien-Kai","middleName":"","lastName":"Lin","suffix":""},{"id":343952584,"identity":"f026c190-3a09-430f-a377-909971309771","order_by":8,"name":"Yen-Yu Cho","email":"","orcid":"","institution":"National Central University","correspondingAuthor":false,"prefix":"","firstName":"Yen-Yu","middleName":"","lastName":"Cho","suffix":""}],"badges":[],"createdAt":"2024-08-14 13:06:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4913834/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4913834/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":66381912,"identity":"0da12adb-5c3c-47ed-bff2-51983c60aa98","added_by":"auto","created_at":"2024-10-11 07:12:39","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":50007145,"visible":true,"origin":"","legend":"\u003cp\u003eStructural and Geological Framework of the Study Area. Figure 1a illustrates the distribution of normal fault systems and submarine volcanoes between the SOT and Taiwan. The study area, MHV, is located along the northeast-southwest trending extension of a normal fault system on the northern side of the rift axis of the SOT (adapted from Tsai et al., 2021). Figure 1b shows the bathymetric map of the study area and its surrounding regions. The map highlights the distribution of 20 deep-tow sonar survey lines and six shipborne sub-bottom profile lines utilized in this study. Detailed information on these survey lines is presented in Table 1. Figure 1c displays photographs of the two deep-tow sonar systems used in this study, the EdgeTech models 2400DSS and 2300B. Among these, the lines marked in yellow, namely Line02, Line08, Line13, and Line20, represent the survey lines used in this study to illustrate the interpretation of the subsurface strata profiles.\u003c/p\u003e","description":"","filename":"Fig01.png","url":"https://assets-eu.researchsquare.com/files/rs-4913834/v1/1c8ad7b010e0983fef765fce.png"},{"id":66380772,"identity":"9d9840a0-5e76-444d-b18a-752fc6f96a0d","added_by":"auto","created_at":"2024-10-11 07:04:39","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":45316929,"visible":true,"origin":"","legend":"\u003cp\u003eNew Seafloor Topography of the MHV Study Area. Figure 2a displays the seafloor topography structure of the MHV and surrounding areas with a grid resolution of 5 meters. The base of the MHV is located at an approximate depth contour of -1350 meters. Figure 2b shows the MHV volcanic cone, illustrating the crater at the volcano's summit and the fracture patterns on its southern flank. Figure 2c provides cross-sectional seafloor profiles along two directions, East-West and North-South, passing through the volcanic crater. The profiles indicate that the crater is approximately 500 meters in width and 80 meters in depth.\u003c/p\u003e","description":"","filename":"Fig02.png","url":"https://assets-eu.researchsquare.com/files/rs-4913834/v1/85644411f5186388181e695f.png"},{"id":66381914,"identity":"a5e80dfb-90a8-4ac6-877a-7637c02112ef","added_by":"auto","created_at":"2024-10-11 07:12:39","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":61440830,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution of hydrothermal vents identified by shipborne sonar in the study area. Figure 3a shows the distribution of MBES data collected during the NOR2-0099 cruise, including hydrothermal vent locations identified by Tsai et al. (2019) using SBES data. Figure 3b provides an example of a WCI captured by MBES, illustrating the appearance of hydrothermal plumes in the water column. Figure 3c maps the distribution of hydrothermal plumes identified using MBES WCI data. Figure 3d shows the temperature-depth profile from XBT data collected during the MBES surveys, with a 1.5°C temperature anomaly observed at station X10 (Figure 3e).\u003c/p\u003e","description":"","filename":"Fig03.png","url":"https://assets-eu.researchsquare.com/files/rs-4913834/v1/5e6e933c6713e1c70e8181c6.png"},{"id":66381917,"identity":"056b3748-c0d3-4fa6-a60a-345e05575d6e","added_by":"auto","created_at":"2024-10-11 07:12:40","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":58837719,"visible":true,"origin":"","legend":"\u003cp\u003eMosaic of side-scan sonar images in the MHV Area. This figure presents a mosaic of SSS images of the MHV region, with a resolution of 1 meter. The distribution of hydrothermal vents, identified through shipborne SBES and SSS water column imagery, is marked on the map. For the analysis of hydrothermal flare distribution, the area has been divided into five zones, Zones 1 ~ 4. The specific characteristics of hydrothermal activity on the seabed in Zones 1 ~ 2 are illustrated in Figures 5 ~ 6, while Zone 3 and Zone 4 are detailed in the upper right and lower right panels of the figure. The locations of \"Devil Chimney\" and \"Witch Mound,\" as identified in the study by Chen et al. (2023), are denoted as D and W, respectively, on the map. Additionally, the positions of seawater temperature anomalies and hydrothermal vents, as reported by Chen et al. (2018) and Chou et al. (2019), are marked as T and P, respectively. In Hsu et al. (2024), the geochemical analysis of sedimentary pore fluids was conducted at four core sampling stations labelled GC1, GC2, GC3, and MC. The location of X10 indicates where this study's XBT observed an increase in seabed temperature.\u003c/p\u003e","description":"","filename":"Fig04.png","url":"https://assets-eu.researchsquare.com/files/rs-4913834/v1/9f71210fbfe9a0550dabbb67.png"},{"id":66380785,"identity":"d603cb7c-fb71-4c71-9ae9-470d19e856e2","added_by":"auto","created_at":"2024-10-11 07:04:45","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":17398912,"visible":true,"origin":"","legend":"\u003cp\u003eMosaic of side-scan sonar images in Zone 1. Figure 5a displays a detailed SSS mosaic of Zone 1, showcasing a high-resolution (0.1 m) seabed image. The mosaic identifies various features associated with hydrothermal activity within the zone. Marked features include areas where hydrothermal flares and chimney structures are evident. Figures 5b and 5c present SSS profiles along specific transects in Zone 1. These profiles provide detailed views of the seabed features and serve as examples for identifying hydrothermal flares and chimney structures, demonstrating the unique sonar signatures associated with these features.\u003c/p\u003e","description":"","filename":"Fig05.png","url":"https://assets-eu.researchsquare.com/files/rs-4913834/v1/778459196960748d0ffdc339.png"},{"id":66380778,"identity":"2d26a274-2593-48e2-95b4-bab3b0ca7708","added_by":"auto","created_at":"2024-10-11 07:04:40","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":60572898,"visible":true,"origin":"","legend":"\u003cp\u003eMosaic of side-scan sonar images in Zone 2. Figure 6a presents the mosaic SSS imagery of Zone 2 with a resolution of 0.1 m. The image highlights the characteristics of hydrothermal activity on the seabed within this zone. Various features indicative of hydrothermal activity are annotated in the image. Figure 6b shows an SSS profile that identifies and exemplifies the characteristics of hydrothermal plumes, chimney structures, and other related features in this area.\u003c/p\u003e","description":"","filename":"Fig06.png","url":"https://assets-eu.researchsquare.com/files/rs-4913834/v1/63eced2272a2d8b9bb9058e6.png"},{"id":66380783,"identity":"701a14a1-f43b-4b2d-82ff-a14c532a11e8","added_by":"auto","created_at":"2024-10-11 07:04:40","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":61512052,"visible":true,"origin":"","legend":"\u003cp\u003eExample of side-scan sonar and sub-bottom profile comparison. This study uses the SSS image segment of Line09, which shows hydrothermal fluid activity on the seabed (Figure a), to compare it with the shallow sedimentary layers in the corresponding sub-bottom profile (Figure b). The image clearly shows flare features and chimney structures on the SSS, which correspond precisely to the distribution of fluid channels in the shallow sedimentary layers of the sub-bottom profile. Fluid channels are directly exposed on the seabed without sediment cover in the areas where chimney structures are distributed.\u003c/p\u003e","description":"","filename":"Fig07.png","url":"https://assets-eu.researchsquare.com/files/rs-4913834/v1/42d9b9c487a33319873ce42d.png"},{"id":66380782,"identity":"8d7fab81-abbb-456c-9b4c-7b36a255daf0","added_by":"auto","created_at":"2024-10-11 07:04:40","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":64560335,"visible":true,"origin":"","legend":"\u003cp\u003eInterpretation of sub-bottom profile for Line13. Figure (a) explains the sub-bottom profile. Figure (b) shows the 230 kHz SSS profile. Figure (c) enlarges the water column image from the SSS, positioned within the cyan dashed box in Figure (b). Figures (d) and (e) magnify specific regions of the sub-bottom profile located within the black dashed boxes in Figure (a). Each annotated feature in the figure is explained in detail in the main text.\u003c/p\u003e","description":"","filename":"Fig08.png","url":"https://assets-eu.researchsquare.com/files/rs-4913834/v1/365ffba6cfb3021d8ee6a7cf.png"},{"id":66381915,"identity":"47875282-c979-4544-b171-555f90fb9b03","added_by":"auto","created_at":"2024-10-11 07:12:40","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":40382960,"visible":true,"origin":"","legend":"\u003cp\u003eInterpretation of sub-bottom profile for Line20. Figure (a) explains the sub-bottom profile. Figure (b) shows the 230 kHz SSS profile. Figure (c) enlarges the water column image from the SSS, positioned within the cyan dashed box in Figure (b). Each annotated feature in the figure is explained in detail in the main text.\u003c/p\u003e","description":"","filename":"Fig09.png","url":"https://assets-eu.researchsquare.com/files/rs-4913834/v1/94d9aa1d30de36e48b71e9b7.png"},{"id":66380774,"identity":"065a5b58-d4b2-48c9-b5d1-f6e9ecc86589","added_by":"auto","created_at":"2024-10-11 07:04:39","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":45951812,"visible":true,"origin":"","legend":"\u003cp\u003eInterpretation of sub-bottom profiler for Line08. Figure (a) explains the sub-bottom profile. Figure (b) shows the 230 kHz SSS profile. Figure (c) enlarges the water column image from the SSS, positioned within the cyan dashed box in Figure (b). Figures (d) magnify specific regions of the sub-bottom profile located within the black dashed box in Figure (a). Each annotated feature in the figure is explained in detail in the main text.\u003c/p\u003e","description":"","filename":"Fig10.png","url":"https://assets-eu.researchsquare.com/files/rs-4913834/v1/1ab27984966b00a647bc4548.png"},{"id":66382154,"identity":"5ca5afa7-48c8-4b61-865f-e2246f2991ba","added_by":"auto","created_at":"2024-10-11 07:20:39","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":47526952,"visible":true,"origin":"","legend":"\u003cp\u003eInterpretation of sub-bottom profiler for Line02. Figure (a) explains the sub-bottom profile. Figure (b) shows the 230 kHz SSS profile. Figure (c) enlarges the water column image from the SSS, positioned within the cyan dashed box in Figure (b). Figures (d) magnify specific regions of the sub-bottom profile located within the black dashed box in Figure (a). Each annotated feature in the figure is explained in detail in the main text.\u003c/p\u003e","description":"","filename":"Fig11.png","url":"https://assets-eu.researchsquare.com/files/rs-4913834/v1/bc9cbb395880d90e567a2cda.png"},{"id":66381918,"identity":"870f796c-b691-42c8-b09a-a3e0c5eb8579","added_by":"auto","created_at":"2024-10-11 07:12:40","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":131872637,"visible":true,"origin":"","legend":"\u003cp\u003ea. Comprehensive Interpretation of Sub-bottom Profilers. This figure presents the extensive interpretation of sub-bottom profiles, where profiles numbered 1 to 21 are arranged from west to east (Figures 15a~d), and profiles numbered 22 to 26 are arranged from north to south (Figure 15e). The figure displays the stratigraphic features related to hydrothermal fluids on sub-bottom profilers. It marks the northern-southern and eastern-western boundaries of the \"Transparent Zone-1\", the stratigraphic feature most associated with seabed morphology within the study area.\u003c/p\u003e","description":"","filename":"Fig12.png","url":"https://assets-eu.researchsquare.com/files/rs-4913834/v1/da104c347e2d5f024dd1bc43.png"},{"id":66382155,"identity":"2e275eb6-37fb-494b-94c2-fd8a3705d03d","added_by":"auto","created_at":"2024-10-11 07:20:40","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":53685025,"visible":true,"origin":"","legend":"\u003cp\u003eA comprehensive diagram of hydrothermal fluid activity features in the MHV region near the seabed. The figure illustrates the analysis of water column data, seabed morphology, and shallow subsurface characteristics related to hydrothermal fluid activity within the MHV area. It is complemented by seabed topography (Figure a) and slope variation analysis results (Figure b), highlighting the extent and impact of hydrothermal fluid activity on seabed morphology within the region.\u003c/p\u003e","description":"","filename":"Fig13.png","url":"https://assets-eu.researchsquare.com/files/rs-4913834/v1/1a3b89d0f7cab4cedf0c1a97.png"},{"id":66380776,"identity":"20592880-2ba2-45df-854f-ecff797be8bd","added_by":"auto","created_at":"2024-10-11 07:04:40","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":50042372,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution map of flares and chimneys in the MHV area. The distribution of chimney structures and hydrothermal plumes on the seafloor, analyzed from side-scan sonar and sub-bottom profiler data, is marked on the side-scan sonar image (with a resolution of 1 meter). The figure clearly shows that the eastern side of the MHV area is the primary region of current seabedhydrothermal activity.\u003c/p\u003e","description":"","filename":"Fig14.png","url":"https://assets-eu.researchsquare.com/files/rs-4913834/v1/e57df950e0911cd1ca5418f6.png"},{"id":66382901,"identity":"f8456dca-1b10-4d04-868b-a8c25cf0e088","added_by":"auto","created_at":"2024-10-11 07:29:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":67088526,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4913834/v1/be14bcb1-d285-4b43-8fd2-571b49a6edba.pdf"},{"id":66380769,"identity":"13d4a856-c09a-4389-abe9-ccecc120e5a0","added_by":"auto","created_at":"2024-10-11 07:04:39","extension":"png","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":199158,"visible":true,"origin":"","legend":"\u003cp\u003eTable 1. Summary of Survey Line Information in This Study. The table below provides detailed information about the survey lines, including the SSS and SBP data collection instruments and their respective frequencies.\u003c/p\u003e","description":"","filename":"Table01.png","url":"https://assets-eu.researchsquare.com/files/rs-4913834/v1/35bcf500065b82e6b58cdd75.png"},{"id":66380771,"identity":"ece16950-6c45-4a64-9ea3-724a6a0def07","added_by":"auto","created_at":"2024-10-11 07:04:39","extension":"png","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":165608,"visible":true,"origin":"","legend":"\u003cp\u003eTable 2. Distribution of Recent Sediment Thickness Above Transparent Zone-1 (TZ-1) in Subsurface Profiles\u003c/p\u003e","description":"","filename":"Table02.png","url":"https://assets-eu.researchsquare.com/files/rs-4913834/v1/07926c5427a57a006bb8d9ef.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"Hydrothermal Activity around the Mienhua submarine volcano in the northern margin of the Southern Okinawa Trough","fulltext":[{"header":"Highlights","content":"\u003cp\u003e1. Upward migration of hydrothermal fluids has produced chimney structures and acoustic transparent zones in strata.\u003c/p\u003e\n\u003cp\u003e2. The hydrothermal activity in the western MHV is no longer active, causing strata subsidence.\u003c/p\u003e\n\u003cp\u003e3. The hydrothermal activity is strong in the eastern MHV.\u003c/p\u003e"},{"header":"1. Introduction","content":"\u003cp\u003eLocated along the eastern edge of the Eurasian Plate, the Okinawa Trough is an active back-arc basin caused by the subduction of the Philippine Sea Plate beneath the Eurasian Plate (Lee et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e1980\u003c/span\u003e; Kimura, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e1985\u003c/span\u003e; Letouzey and Kimura, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e1986\u003c/span\u003e; Sibuet et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e1987\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e1995\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e1998\u003c/span\u003e; Hsu et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Tsai et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The Okinawa Trough extends from Kyushu Island in southwest Japan to the Ilan Plain in northeast Taiwan. It can be divided into the Southern Okinawa Trough (SOT), the Middle Okinawa Trough (MOT), and the Northern Okinawa Trough (NOT). The segmentations are based on the structural boundaries of the Tokara Fault and the Kerama Gap (Kodaira et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e1996\u003c/span\u003e; Shinjo et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Fabbri et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Gungor et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). The SOT is under a fast rifting because of the post-collision and transition from collision to subduction of the Philippine Sea Plate (Hsu, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Tsai et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). However, the actual back-arc rifting of the Okinawa Trough terminates near 122\u003csup\u003eo\u003c/sup\u003e20\u0026rsquo;E (Tsai et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). To the west of 122\u003csup\u003eo\u003c/sup\u003e20\u0026rsquo;E, the former NE-SW trending structures of the proto-Taiwan mountain belt are still evident (Tsai et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Due to the southward migration of the southern Ryukyu arc and the rollback of the Philippine Sea Plate, the back-arc region undergoes substantial tectonic extension. This extension leads to pronounced hydrothermal activity in the Southern Okinawa Trough (SOT) region, where intense interactions between geological processes drive the formation of hydrothermal systems. These systems contribute significant heat and mass transfer from the Earth's interior, fostering unique chemical and biological environments. The resulting hydrothermal vents and associated mineral deposits offer valuable insights into the dynamics of seafloor spreading and the complex interplay between tectonic stress and magmatic activity. Volcanism or hydrothermal activities are very active and mainly distributed along the central depression or in the southern portion of the SOT (Tsai et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). In contrast to most submarine volcanoes in the central depression of the SOT, the Mienhua Submarine Volcano (MHV) is located in the northern margin of the SOT (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). The lower reaches of the Mienhua Submarine Canyon (MHC) flow through the north side of the MHV (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb).\u003c/p\u003e \u003cp\u003eSeafloor rift valleys and mid-ocean ridges are tectonic landforms due to the divergent movement of Earth's tectonic plates. These features occur in geologically active regions, making them common sites for forming hydrothermal vents. Crustal fractures of faults provide pathways to facilitate the development of hydrothermal circulation. Hydrothermal circulation system observations mainly focus on hydrothermal flares (Massoth et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e1988\u003c/span\u003e; Morton et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e1956\u003c/span\u003e). Hydrothermal flares are generated when superheated water within the Earth's crust is expelled through vent openings due to pressure differences. During the ascent of the flare, surrounding seawater continuously mixes with the hydrothermal fluid, causing the flare to dissipate until the upward force balances with the surrounding water; at this point, the flare phenomenon dissipates laterally. In regions with active hydrothermal circulation, deep volcanic materials are carried out by the hot water, creating areas with smoke-like appearances. When hydrothermal fluids carry heavy metals such as manganese and iron, \"Black Smokers\" could be formed (Tivey et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e1995\u003c/span\u003e). Black smokers are significant conduits for exchanging materials between seawater and the crust.\u003c/p\u003e \u003cp\u003eTo understand the distribution of hydrothermal activity in the SOT back-arc basin, Tsai et al. (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) used a 38 kHz single-beam echo sounder (SBES) to observe gas bubbles out of the seabed associated with hydrothermal activity. They detected a total of 266 acoustic images indicative of active hydrothermal vents, including those in the MHV study area (marked by green dots in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). Tsai et al. (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) also noted that hydrothermal vents are mainly located along the rift axis of the Okinawa Trough. To better understand the ongoing volcanic activities, Tsai et al. (\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) conducted deep-tow sub-bottom profiler (SBP) and side-scan sonar (SSS) surveys across the entire back-arc basin of the SOT. Their results show that active volcanism in the SOT mainly occurs in the southern half of the back-arc basin. The volcanic activity occurs along several linear or branching zones roughly parallel to the trough axis. On the other hand, the northern half of the back-arc basin exhibits a little volcanic activity but features more brittle normal faults.\u003c/p\u003e \u003cp\u003eThe areas of active hydrothermal vents display high-temperature and high-pressure fluids expelling into the seawater. These fluids originate from the deep Earth and contain large amounts of minerals and chemicals. This phenomenon significantly impacts geological processes in the sea, such as volcanic activity, sedimentation, and biological ecosystems. These hydrothermal vents often appear in fissures or volcanic areas on the seafloor. The expelled hydrothermal fluids react chemically with the surrounding cold seawater, forming unique geological structures such as black smokers. Additionally, these areas attract biological communities that depend on the chemical energy from hydrothermal vents for survival, including crabs, shrimp, worms, and various microorganisms. The importance of these features in marine environments has been highlighted by Von Damm (\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e1990\u003c/span\u003e), Haymon et al. (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e1993\u003c/span\u003e), Baker and German (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2004\u003c/span\u003e), and Kelley et al. (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2005\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTo better understand hydrothermal activities, Chen et al. (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) and Chou et al. (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) employed a Fiber-optical Instrumentation Towed System (FITS) to explore the flat area on the eastern side of the MHV and hilly regions on the southern side. They have identified a near-seafloor temperature anomaly of 0.2\u0026deg;C (from 4.4\u0026deg;C to 4.6\u0026deg;C). They also observed characteristics of hydrothermal seepage in sediment surrounded by biological communities. In contrast, although significant rocky features were found in the uplifted regions of MHV, no biological communities were observed there. Using ROV observations, Chen et al. (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) presented two chimney structures emitting hydrothermal flares referred to as the Witch Mound and the Devil Chimney on the eastern side of MHV. Backscatter data obtained from a multi-beam echo sounder (MBES) system showed that these chimneys exhibited high backscatter intensity characteristics. The hydrothermal fluids within the sediments on the east side of MHV were analyzed and showed that the temperature of the hydrothermal fluids in this region likely surpasses 350\u0026deg;C (Hsu et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe previous results indicate notable features of hydrothermal circulation activities in the MHV region. To provide better acoustic images, we use a deep-tow sonar system to collect side-scan sonar (SSS) and sub-bottom profiler data around the MHV (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec). We aim to comprehensively understand the seabed features of the hydrothermal activity of the MHV.\u003c/p\u003e"},{"header":"2. Data collection and processing","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 High-resolution deep-tow sonar data\u003c/h2\u003e \u003cp\u003eThe deep-tow sonar data used in this study were collected from three survey cruises. These data were mainly collected using the EdgeTech 2300B deep-tow sonar system. However, Line 11 was collected using the EdgeTech 2400DSS deep-tow sonar system. The 2400DSS deep-tow sonar system operates with SSS frequencies of 120 kHz and 410 kHz, and the chirp frequency range of SBP is 1\u0026ndash;10 kHz. The 2300B deep-tow sonar system, on the other hand, has higher SSS frequencies of 230 kHz, 540 kHz, and 850 kHz, and a SBP with a four-transducer array operating within the same frequency range of 1\u0026ndash;10 kHz. Compared to the 2400DSS, the 2300B system offers higher-resolution seabed imagery and deeper sediment penetration. The data utilized in this study include both SSS and SBP records. Basic information regarding each survey line, numbered from 01 to 20, is provided in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. To facilitate data integration and organization, the deep-tow sonar data were renumbered from the east side of MHV to the west (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). The deep-tow sonar instrument was towed at a speed of ~\u0026thinsp;2 knots and deployed at approximately 30 to 50 meters above the seafloor.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Bathymetry and water column data\u003c/h2\u003e \u003cp\u003eThe bathymetric data of 20-meter resolution in this study area were collected using the Atlas MD50 MBES system (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb) (Tsai et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). During the acquisition of LGD2307 and NOR2-0099 deep-tow sonar and shipborne sub-bottom profiler data, EM122 and EM712 were simultaneously operated along the survey lines. To increase the resolution of the bathymetry in the MHV study area, we conducted a detailed difference analysis on the bathymetric data between the EM122 and the EM712 systems. We compared the beam depths, and the results showed that the depth difference variance ranges from \u0026minus;\u0026thinsp;5 meters to 10 meters, with an average of +\u0026thinsp;2.35 meters. The depth values from the EM712 data were corrected based on the average depth difference of +\u0026thinsp;2.35 meters. Using the EM122 depth distribution as a baseline, we integrated the corrected data from both systems to produce a 5-meter grid resolution seafloor topography map. We employed Globe software (Poncelet et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) to compile the corrected data, generating a high-resolution seafloor topography dataset (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), the foundational layer for analyzing the MHV area.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eEcho sounders EM122 and EM712 have also recorded the water column image (WCI) data. Being a deep-sea survey sonar, the EM122 operates at low frequencies (10.5\u0026ndash;13.5 kHz) and employs longer pulse lengths, allowing it to probe deep waters but with lower WCI resolution. In contrast, the EM712, with its mid-frequency range (40\u0026ndash;100 kHz) and shorter pulse lengths, provides higher WCI resolution. This study utilized the Caris software to process bathymetric data to identify and map hydrothermal vent flares. For example, the water column imagery shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea identifies hydrothermal vent flares in the central axis water column profile along the survey line (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb). These identified flares closely match the distribution clusters of hydrothermal vents delineated by Tsai et al. (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) using SBES (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). By examining single WCI cross-sections, this study systematically mapped the distribution and morphological characteristics of the hydrothermal vents, resulting in a detailed hydrothermal vent distribution map and their associated seafloor topography (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eInterestingly, in the vicinity of the hydrothermal vent clusters east of MHV, an XBT-T5 station X10 recorded a temperature increase of 1.5\u0026deg;C near the seabed, which is atypical compared to other stations (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed). This elevated temperature persisted throughout the recording duration of the XBT (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee), indicating the widespread presence of hydrothermal vents in this area.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Seafloor morphology of MHV","content":"\u003cp\u003eMorphologically, the MHV is broadly conical. The summit of the volcanic cone is located at a depth of around \u0026minus;\u0026thinsp;1170 meters, while its base is at approximately \u0026minus;\u0026thinsp;1350 meters. The volcanic cone has an elevation of about 180 meters and a spatial extent of roughly 2.9 km\u003csup\u003e2\u003c/sup\u003e (Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea and \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). A prominent depression or a volcanic crater is observed at the summit of MHV (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). This crater-like feature has a diameter of around 500 meters and a depth of approximately 80 meters, as shown in Profile pp\u0026rsquo; of Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec. The southern side of the crater was breached, indicating a possible erosion or collapse (Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb and \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec, Profile tt\u0026rsquo;). The seafloor surrounding MHV displays significant variation of morphology. To the north and south of the volcano's base, within a distance of about 0.5 km, and to the west, within about 1.5 km (the region between the black dashed lines and MHV in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea), the seafloor topography exhibits undulating features. In contrast, the eastern side of MHV is relatively flat. Additionally, the southern bank of MHC has collapsed, as indicated by the red dashed area in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea. The detailed bathymetric survey conducted in this study provides a comprehensive understanding of the MHV's morphology, highlighting its conical shape, crater-like depression, and significant morphological variation in the surrounding area.\u003c/p\u003e \u003cp\u003eSubmarine volcanoes are usually formed due to magma eruptions resulting from tectonic activity. As magma ascends, it breaks through weak spots in the crust, erupting onto the seabed. The erupted magma cools and solidifies, accumulating into a volcanic cone. Volcanic activity releases significant amounts of heat, gases, and minerals into the ocean, often associated with the formation of hydrothermal deposits (Umbgrove, \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e1950\u003c/span\u003e; White, \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Kase, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Costa et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Tsai et al. (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) have identified numerous hydrothermal venting sites around the volcanic structure, primarily located on the eastern and southwestern gentle slopes of the MHV (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). The XBT station X10 shows a temperature anomaly of approximately 1.5\u0026deg;C (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee) at the seafloor (marked by a star in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). This study will investigate the causes of seafloor temperature anomalies through deep-tow SSS and SBP analyses. Additionally, it explores why the western side of MHV exhibits large-scale depressed topography and the absence of hydrothermal vents in this area, which instead tend to occur in more gently sloping regions.\u003c/p\u003e"},{"header":"4. Hydrothermal circulation characterized by SSS and SBP","content":"\u003cp\u003eThe detailed SSS images are essential to describe submarine hydrothermal vents. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows the deep-tow SSS observations of hydrothermal vents on the seabed of the MHV area. In contrast to sediments, rocks in SSS images appear as blocks or stripes with varying brightness and texture. These characteristics are mainly due to various rock types' different acoustic impedance properties. High-reflectivity rocks usually show bright areas, while low-reflectivity sediments appear as dark regions (Savini, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; McMullen et al., 2014; Burguera and Oliver, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eOn the other hand, sediments are loose materials deposited on the seabed and have a density close to seawater, resulting in weaker sonar reflections. In SSS images, sediments are generally represented by flat or undulating terrain with lower reflectivity signals (McMullen et al., 2014). The distinction lies in those sediments, due to their loose structure and lower density, absorb more acoustic energy, resulting in lower backscatter intensity in the images (Savini, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Burguera and Oliver, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The SSS seabed images in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e reveal that apart from regions with significant signal strength fluctuations due to poor instrument dynamics and localized strong backscatter signals in Zone 1 (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003ea) and Zone 2 (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003ea), the seabed in the vicinity of MHV predominantly exhibits low backscatter intensity features. This suggests that loose sediments mainly cover the surface of this area.\u003c/p\u003e \u003cp\u003eThe SBP is a useful tool to understand the shallow subsurface layers of the seabed. It involves acoustic waves (sonar) that penetrate the seabed and reflect off various sediment layers, providing detailed images of the geological structures beneath the seabed. An acoustic transparent zone could reflect hydrothermal vent areas when using a sub-bottom profiler to observe hydrothermal circulation systems. The transparent zones are characterized by the lack of clear reflection from the sediment layers in the seabed. These zones typically correspond to fine-grained sediments or fluid-saturated layers, which have a very low or no acoustic impedance contrast and produce weak or no reflection signals.\u003c/p\u003e \u003cp\u003eThe formation of transparent zones in sub-bottom profiles in hydrothermal circulation areas are multifaceted and complex. According to Germanovich et al. (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2011\u003c/span\u003e), these transparent zones near hydrothermal vents are generally attributed to hydrothermal sediments and the accumulation of biological materials. The intense thermal and chemical activities associated with hydrothermal vents lead to the deposition of minerals such as sulfides, sulfates, and silicates, which can create porous structures that absorb sound energy. These activities influence sediment deposition in the surrounding areas, where fine particles precipitated from hydrothermal flares can settle and form distinct layers in the sediment record. Due to their fine grain size and homogeneous composition, these transparent zones may appear in the substrate profiles (Cann et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1997\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eFurthermore, minerals precipitated from hydrothermal fluids, such as sulfides, can form layers with different acoustic properties. If these layers are fine-grained and uniform, they might not strongly reflect sonar waves and thus appear as transparent zones in the sub-bottom profiles (Hannington et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1995\u003c/span\u003e). The thermal and chemical activities associated with hydrothermal vents can alter the surrounding sediments and rocks, potentially changing the physical properties of the materials. If such changes produce more homogeneous and finer-grained materials, they may form transparent zones (Stoffers et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e1994\u003c/span\u003e; Johnson and Holmes, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e1989\u003c/span\u003e). Singh et al. (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) also noted that accumulating organic matter due to high biological productivity around the vents contributes to forming these transparent zones. In summary, the transparent zones observed in sub-bottom profiles in hydrothermal circulation areas are closely linked to hydrothermal activity, either directly or indirectly.\u003c/p\u003e \u003cp\u003eThis study focuses on the segment along Line09 where hydrothermal activity was detected (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003e; profile location as indicated in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The SSS imagery in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003ea reveals distinct hydrothermal and chimney features on the seabed, along with multiple flare phenomena within the water column. These hydrothermal features observed beneath the SSS instrument correlate well with the stratigraphic characteristics observed in the substrate profile (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003eb). Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003ea shows hydrothermal activity and chimneys are prominently visible on the seabed, and multiple flare phenomena are present in the water column. This image highlights the interaction between the seabed structures and the overlying water column, indicating active hydrothermal discharge zones. The sub-bottom profile results in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003eb reveal that the shallow strata in this region appear to be influenced by hydrothermal fluids. Additionally, the maximum penetration depth of the sub-bottom profiles in this study is approximately 100 meters. To adequately highlight and differentiate the characteristics of shallow high-resolution strata affected by hydrothermal activity, the strata with no reflective signals are classified into three categories: fluid channels, transparent zones and blanking zones (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003eb).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThese fluids migrate upwards through minor normal faults or fractures, cutting through sedimentary layers and forming numerous fluid channels. These channels indicate pathways that allow hydrothermal fluids to ascend towards the seabed. The sub-bottom profile suggests that many fluid channels have merged, creating extensive blanking zones, especially beneath areas with numerous chimney structures (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003ea). These blanking zones are regions with weak or absent seismic reflection signals, typically caused by fluids that absorb or attenuate the acoustic energy. This phenomenon is commonly associated with hydrothermal areas where fluid saturation disrupts the reflection of sound waves. In regions of the shallow strata that the fluids have not fully penetrated, a substantial transparent zone (TZ) is formed, covered by approximately 5\u0026ndash;6 meters of sediment (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003eb). This transparent zone is characterized by the absence of clear reflection signals, suggesting that it consists of fine-grained, homogeneous materials that do not reflect sonar waves effectively. Even in the strata where some reflection signals can still be detected (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003eb), there is evidence of fluid intrusion that reduces the impedance contrast between layers. This reduction in impedance contrast decreases the strength of layer reflection signals, indicating ongoing fluid infiltration. The gradual reduction in signal strength within these strata points to the progressive invasion of hydrothermal fluids, altering the physical properties of the layers and diminishing their ability to reflect acoustic waves effectively.\u003c/p\u003e \u003cp\u003eBy comparing images from SSS and SBP directly beneath, this study identifies the locations of hydrothermal chimneys and flare features (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003ea) occurring within sedimentary layers where hydrothermal fluids migrate upward (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003eb). These sections mostly coincide with the distribution of fluid channels, indicating the upward migration of hydrothermal fluids through the overlying sediments. The SBP data shows that sedimentary layers infiltrated by hydrothermal fluids no longer display clear layering information. Additionally, the study finds that while SSS effectively resolves the morphology of chimneys, the corresponding substrate profile exhibits cone-shaped diffraction signals with relatively weaker intensities (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003eb). This is likely due to the broader beam width of the SBP (the emission angles vary with frequency as follows: about 180\u0026deg; at 1 kHz, 62\u0026deg; at 3 kHz, and 30\u0026deg; at 6 kHz in the SBP mode of the EdgeTech 2300B), compounded by the influence of hydrothermal flares, thereby reducing the clarity of chimney detection. In summary, employing deep-tow sonar systems, this study effectively demonstrates the impact of deep-seated hydrothermal fluid migration on sedimentary layers near the seabed, as evidenced by their reflection characteristics in sub-bottom profiles compared with hydrothermal activity zones observed in SSS imagery.\u003c/p\u003e"},{"header":"6. The area of hydrothermal vents","content":"\u003cp\u003eHydrothermal vents typically display point-like or patchy features with strong backscatter intensity in the SSS images (e.g., Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003eb, feature b1, the enlarged figure is located at the top right panel). The backscatter is due to the difference of acoustic impedance between the venting hydrothermal fluids and the surrounding seawater. Figures\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003eb, \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003ec, and \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003eb illustrate three examples of the SSS seabed images of numerous point-like or patchy high-backscatter features. These features indicate hydrothermal seepage areas, providing exact locations of hydrothermal activity on the seabed. Feature c1 (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003ec, the enlarged figure located at the center right) shows another high-backscatter area at site X10, where a temperature anomaly was observed (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee). Although site X10 does not align with the previously recorded hydrothermal vent locations from the SBES (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), the new data from the deep-tow SSS confirms that X10 lies within the area of strong backscatter. The studies by Chen et al. (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) and Chou et al. (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) observed that at locations where near-seafloor temperature increases, there are noticeable hydrothermal flares (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003ec, feature c2; enlarged view located in the bottom right panel).\u003c/p\u003e \u003cp\u003eHydrothermal fluid leaking into the water column is called hydrothermal flare. In the SSS water column images, flares typically appear as streaks or cloud-like features with a directional spread. This is because the fluid in the flares has a different density than the surrounding seawater, leading to an enhanced scattering signal from the sonar (Baker and German, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; German and Von Damm, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Juniper and Sibuet, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e1987\u003c/span\u003e). Many of these flares were observed in the SSS water column data in Zones 1 and 2, as described in Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003eb, \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003ec, and \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003eb. Notably, when the towed instrument passes through hydrothermal emission areas, a continuation of the flare structure from the seabed to the water column is observed (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003eb).\u003c/p\u003e \u003cp\u003eThe pore water in the MHV hydrothermal field (the core locations for these findings are illustrated in Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003ea and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003ec) has a significant decrease in magnesium ion (Mg\u0026sup2;⁺) concentration and a substantial increase in lithium-ion (Li⁺) concentration, indicating the influence of high-temperature hydrothermal fluids (Hsu et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The hydrothermal fluids in the region may have a temperature exceeding 350\u0026deg;C and could migrate upward through the sediments at a rate of 0.13 to 124 cm/year.\u003c/p\u003e \u003cp\u003eNumerous hydrothermal vents have been identified on the south side of the MHV volcanic cone (Zone 3 of Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). These vents are characterized by significant flare features in the water column by the SSS, indicating a high intensity of hydrothermal seepage (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The hydrothermal vent images identified by the FITS (Chen et al., 2017; Chou et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) are also located in this area (P mark in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). It is noted that no active hydrothermal vents had been detected by SBES in the western side of the MHV water column data (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). However, this study's SSS images show two potential hydrothermal seepages in Zone 4 (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), with flare characteristics indicating the presence of weak hydrothermal leakage (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Compared to Zone 1, Zone 2 and Zone 3, the seepage intensity in Zone 4 appears significantly weaker. This highlights that shipborne sonar systems cannot easily detect hydrothermal vents with lower intensity.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e6.1 Seafloor features of hydrothermal chimneys\u003c/h2\u003e \u003cp\u003eHydrothermal chimneys are conduits in hydrothermal circulation systems. Metal-sulfide-rich hydrothermal fluids are expelled through the chimneys. Vertical or inclined rod-like or conical features typically characterize these chimneys. Our study identified numerous black smoker features correlated to hydrothermal vents on the seabed imagery from the eastern side of MHV, specifically within Zone 1 (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003ea). According to the seabed imagery examples (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003eb and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003ec), black smokers in this area are predominantly distributed within regions marked by point-like or patchy high-backscatter signals indicative of hydrothermal vents. These black smokers usually exist in clusters. The variations in signal strength and shadow lengths in the SSS imagery suggest these black smokers have a rough appearance. When the towed SSS instrument passes directly over a black smoker, hydrothermal flares emitting into the water column can be observed (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003eb, feature b1). The black smoker Devil Chimney (Chen et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), is situated within the black smoker group in Zone 1, as shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003ea and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003eb (marked as D). Another black smoker, Witch Mound (Chen et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), has high-backscatter signals and hydrothermal venting but seems not to have developed into a fully formed black smoker yet (marked as W in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003ea, bottom right).\u003c/p\u003e \u003cp\u003eThe hydrothermal vent areas located west and south of MHV (Zone 2 in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) present distinct characteristics of SSS seabed imagery (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003ea). The chimneys display individual mounds (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003eb). This area shows hydrothermal vents with limited distribution, characterized by point-like or patchy high-backscatter signals, but with generally lower backscatter intensity compared to the chimneys in Zone 1 (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003eb). The SSS imagery indicates that the seabed in Zone 2 is heavily covered with sediments. The chimney structures are individual mounds and do not display prominent seabed features. It is hypothesized that the hydrothermal fluids may mix with cold seawater within the sediment layer, causing the metals to precipitate as sulfides within the substratum. This process could form white smokers or diffuse flows where the fluids percolate through the seabed without forming distinct chimneys.\u003c/p\u003e \u003cp\u003eIn the hydrothermal vent area at the southern base of MHV (Zone 3 in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), SSS seabed imagery reveals point-like or patchy high-backscatter signals and linear features (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, top right inset). However, when these sonar features are overlaid with seabed topography (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), the SSS characteristics of Zone 3 primarily reflect the topographic variations rather than active black smoker structures. The hydrothermal activity in this region is likely due to fluids seeping through fractures in the near-seabed volcanic terrain of MHV. Additionally, the hydrothermal seepage areas in Zone 4 (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, bottom right inset) primarily reflect seabed topographic variations. No significant chimney structures have been detected in these zones, suggesting that the hydrothermal fluids might seep diffusely through the seabed without forming notable chimney features.\u003c/p\u003e \u003cp\u003eBased on observations from the deep-tow SSS images, the hydrothermal circulation at the MHV is currently active on its eastern side, particularly in Zone 1 (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). This area is characterized by considerable hydrothermal discharge and abundant black smoker structures. The seabed in this zone contains hydrothermal vents and chimney formations, indicating ongoing and vigorous hydrothermal activity. In contrast, the southwest area (Zone 2 in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) and the southern volcanic cone of MHV (Zone 3 in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) exhibit only localized hydrothermal activity. The hydrothermal discharge in these areas is limited, with smaller venting zones and less defined chimney structures. The SSS imagery in these regions shows hydrothermal emissions are more sporadic and less intense than in Zone 1. The limited and diffuse nature of the hydrothermal activity in Zones 2 and 3 suggests that these areas are farther from the primary hydrothermal circulation system.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e6.2 Shallow strata features of hydrothermal chimneys\u003c/h2\u003e \u003cp\u003eWe collected 20 deep-tow sub-bottom profiler and SSS data (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Here, we focus on the influence of hydrothermal activity on the shallow substrata in the MHV region. One profile crossing the central MHV body and three profiles on the eastern side are particularly shown here (Figs.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e11\u003c/span\u003e; Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The analysis elucidates the impact on shallow substrata in the presence of hydrothermal activity and chimney features in the MHV area.\u003c/p\u003e \u003cp\u003e(a) Sub-bottom profile Line13\u003c/p\u003e \u003cp\u003eThis profile is located on the western side of MHV and represents the closest line to the MHV summit (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). From northeast to southwest, this profile shows characteristics of fluid channels and fractured geological layers between 8.5 and 8 km near the southern embankment of MHC (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e8\u003c/span\u003ea). The seabed exhibits significant undulations toward 8-3.5 km. It is partly covered by ~\u0026thinsp;5 m thick sediment, and a pronounced blanking zone is observed beneath the sediment layers, which are indistinguishable (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e8\u003c/span\u003ea). Between 3.5 and 2.5 km, sediment layers are interrupted by large-scale fluid channels, cutting through two transparent zones (TZ-1 and TZ-2, as labelled in this study). There is a\u0026thinsp;~\u0026thinsp;5 m thick layer of sediment in the seabed where TZ-1 exist. At 3.5 km, the seabed topography changes from steep undulation on the northeast to a gentle slope on the southwest, coinciding with the occurrence of hydrothermal venting in the water column located in the transition zone of this topographic change (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e8\u003c/span\u003ec; profile position within the cyan dashed box area in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e8\u003c/span\u003eb).\u003c/p\u003e \u003cp\u003eAdditionally, between 4 and 3 km, cone-shaped geological features of possible chimneys are observed. Comparison with the corresponding SSS data shows similar protrusions in both seabed and water column images (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e8\u003c/span\u003ec), though these chimney features are less distinct than those in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e8\u003c/span\u003e. TZ-1 is separated at ~\u0026thinsp;1.5 km, and the geological layers on both sides show significant tilting, especially with a larger tilt angle on the northeast side (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e8\u003c/span\u003ed). Below this area, characteristics such as normal faults, fractures, and small-scale fluid channels are observed in the underlying layers. Within the distance between 1.5 and 0 km, the transparent zone TZ-3 is identified beneath a sediment layer of ~\u0026thinsp;30\u0026ndash;40 m thick. Unlike the transparent zone near the seabed on the northeast side, TZ-3 retains identifiable layer sequences, with deposition patterns and tilt angles nearly identical to the sediment layers above and below it (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e8\u003c/span\u003ee).\u003c/p\u003e \u003cp\u003e(b) Sub-bottom profile Line20\u003c/p\u003e \u003cp\u003eThis profile represents the westernmost sub-bottom profile collected in MHV as part of this project (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb), where no intense seabed topographic features were observed. There are also no blanking zones indicating completely indiscernible stratigraphic sequences in the subsurface (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e9\u003c/span\u003ea). Instead, within the distance between 10 and 7.5 km, the clear acoustic transparent zone TZ-1 exists, together with numerous fluid channels intersecting and penetrating the strata (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e9\u003c/span\u003ea). The TZ-1 layer is overlain by ~\u0026thinsp;5 meters of modern sediment, but the SSS seabed and water column images in the region did not reveal any chimneys or hydrothermal flare features (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e9\u003c/span\u003ec; delineated by the cyan dashed box in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e9\u003c/span\u003eb). Towards the southwest, at ~\u0026thinsp;5.5 km distance, three acoustic transparent zones (TZ-3, TZ-4, and TZ-5) are found. According to the subsidence or uplift reference line on this profile, the seafloor elevation within this area indicates a maximum change of approximately 60\u0026ndash;70 m.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e(c) Sub-bottom profile Line08\u003c/p\u003e \u003cp\u003eThis profile is located near the center of a hydrothermal vent on the eastern side of the MHV (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). Compared to Line13 (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e8\u003c/span\u003e), in the segment between 6.2 and 4.2 km of the hydrothermal activity, no blanking zones is observed (Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e9\u003c/span\u003e). Instead, there are fluid channel features intersecting and penetrating through the strata (Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e10\u003c/span\u003e). However, unlike Line20, the seabed of Line08 exhibits a feature of abundant hydrothermal vents and chimneys in the SSS imagery (Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e10\u003c/span\u003ec, delineated by the cyan dashed box in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e10\u003c/span\u003eb). These features also appear in the sub-bottom profile. This indicates that the 6.2\u0026ndash;4.2 km segment of the Line08 represents a main location where hydrothermal fluids occur in the seabed. The hydrothermal activity is vigorous, suggesting this region is in a mature stage of hydrothermal activity.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe most significant difference between Line08 and other profiles on the eastern side of MHV is TZ-1 layer connects directly with the main hydrothermal body at the distance of ~\u0026thinsp;4.2 km. The TZ-1 layer here is thinner compared to profiles on the western side of MHV (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e8\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e9\u003c/span\u003e). There is no subsidence evidence in the layers beneath TZ-1. Instead, they are overlaid by ~\u0026thinsp;5 meters thick sediment (Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e10\u003c/span\u003ed). Besides TZ-1, the Line08 sub-bottom profile also show TZ-2 and TZ-6 acoustic transparent zones (Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e10\u003c/span\u003ea). According to the reference line of subsidence or uplift in this section, changes in seafloor elevation near the hydrothermal activity area show a maximum downward movement of about 10\u0026ndash;20 meters. This indicates that hydrothermal fluid flow can significantly influence dynamics of the strata.\u003c/p\u003e \u003cp\u003e(f) Sub-bottom profile Line02\u003c/p\u003e \u003cp\u003eThis profile is located exactly at the eastern boundary of hydrothermal vent activity on the seabed of MHV (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). Compared to Line13 (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e8\u003c/span\u003e), sub-bottom profile Line02 contains hydrothermal fluids which gradually ascend into the strata (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e11\u003c/span\u003ea). At the distance of 5 km, a small-scale hydrothermal flare is shown in the SSS imagery (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e11\u003c/span\u003ec; delineated by the cyan box in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e11\u003c/span\u003eb). Unlike other profiles, acoustic transparent zone TZ-1 is developed. However, at approximately 30\u0026ndash;40 meters below the seabed, the sub-bottom profile show TZ-2 previously intersected by fluid channels, and TZ-6 located at 70\u0026ndash;80 meters below the seabed (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e11\u003c/span\u003ed). The sedimentary layers and geological trends observed in Line02 indicate a southwestward dipping structure (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e11\u003c/span\u003ea) consistent with the topography. All these observations suggest that this region is in a developing stage of hydrothermal activity. Additionally, although hydrothermal activity has not completely occupied the shallow seabed on this profile, there is already a seafloor variation of ~\u0026thinsp;5\u0026ndash;10 meters in the central hydrothermal activity zone (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e11\u003c/span\u003ea). This demonstrates that within the central hydrothermal activity zones, ongoing intrusion of hydrothermal fluids continues to affect the shallower layers.\u003c/p\u003e \u003c/div\u003e"},{"header":"7. Integrated interpretation of the MHV morphology","content":"\u003cp\u003eHere shows the interpretation from 20 northeast-southwest oriented deep-tow sub-bottom profiles and one shipboard sub-bottom profile from west to east (Figs.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ea-\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ed; profile locations as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb; profile information as shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Figures\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ea and \u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003eb are located on the west side of MHV, while Figs.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ec and \u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ed are on the east side of MHV. Additionally, the study includes results from 5 northwest-southeast oriented shipboard sub-bottom profiles (Fig.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ee; profile locations are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb; profile information is shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Based on 26 sub-bottom profiles, we could better understand the different geological features related to the hydrothermal activity in the seabed of the MHV region. The interpretations are as follows:\u003c/p\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eComparison with SSS seabed and water column hydrothermal features reveals that the blanking zones and transparent zone in the seabed of the MHV region are geological features caused by hydrothermal activity. As deep-seated hydrothermal activity migrates upwards through minor normal faults or fractures to form fluid channels, several transparent zones can sequentially develop. In this study, the shallowest transparent zone in the MHV area is marked as Transparent Zone-1 (TZ-1) (Fig.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003e).\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eAs deep-seated hydrothermal activity migrates upwards and diffuse outward, these transparent zones gradually connect with the main conduit of the hydrothermal activity (see Lines 01\u0026ndash;09 in Figs.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ec-d). If the deep hydrothermal fluids continue to migrate upward, they will eventually penetrate the sedimentary layers, forming a blanking zone (as observed in Lines 10\u0026ndash;17 in Figs.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ea-c). However, suppose the upward migration of deep hydrothermal fluids stop, the layers beneath the transparent zone will not be completely invaded by the hydrothermal fluids, resulting in a geological feature where fluid channels coexist with sedimentary layers without forming a blanking zone (as observed in Lines 18\u0026ndash;20 in Fig.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ea). This scenario illustrates that the migration activity of deep-seated hydrothermal fluids can vary with the change in spatiotemporal conditions and affect the hydrothermal activity features near the seafloor.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eIn the area where the TZ-1 is distributed, the strata incline towards the summit of the MHV (as seen in Lines 10\u0026ndash;20 in Figs.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ea-c). Besides, the integrated sub-bottom profile diagram reveals that the overall topographic gradient slopes from the northeast to the southwest. The strata beneath both flanks of the TZ-1 incline towards the blanking zone. This study indicate that the strata affected by hydrothermal activity display gradual subsidence, forming minor normal faults or fractures, creating new fluid channels, and allowing hydrothermal activity to spread around the MHV gradually.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe large-scale, rugged topographic features observed on the morphology of the MHV area (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) are almost located within the distribution range of the blanking zone in the sub-bottom profiles (Lines 10\u0026ndash;17 in Figs.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ea-c). Significant morphological undulations are also observed in most active areas of hydrothermal activity, such as the region between Lines 07 and 09 (Fig.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ec). The persistent influence of hydrothermal intrusions has caused gradual subsidence and weakening of the sedimentary layers around MHV. Finally, large-scale mass collapse may occur because of the inability to withstand the overlying gravity. The collapsed MHC escarpment, located northeast of MHV (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), could be associated with the hydrothermal activity as evidenced by the distribution of TZ-1 and fluid channels in the sub-bottom profiles between Lines 11\u0026ndash;14 in Fig.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003eb. Since the MHV consists of igneous rocks, it maintains its high topographic feature.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe hydrothermal activity has weakened the seabed of the western and southern sides of MHV. The TZ-1 is overlain by about 5 meters sediments, which constrain the formation of chimney-like structures (Line13 and Line17 in Fig.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ea and Fig.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003eb). Therefore, almost no chimney structures are found in the seabed in the western and southern sides of MHV.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eIn the eastern side of the MHV, numerous chimney-like features are observed (e.g. Lines 8\u0026ndash;10 of Figs.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ec and \u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ed). The subsurface layers in this region show that deep-seated hydrothermal fluids have migrated upwards through fluid channels, near the seafloor. The deep hydrothermal activity in the MHV region is active now in the eastern side. Because of the upward migration and infiltration of these hydrothermal fluids into surrounding strata, hydrothermal processes are developing eastward (e.g. Line07 to Line02 in Figs.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ec and \u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ed). Line01 in Fig.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ed demonstrates that the deep hydrothermal activity is at ~\u0026thinsp;20\u0026ndash;30 meters below the seafloor. It is inferred that the current hydrothermal activity in the eastern side of the MHV is active in the area between Line01 and Line02 (Fig.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ed).\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe distribution of TZ-1 (from Lines 4 to 26 in Fig.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003e) indicates that the sediment subsidence area is mainly due to hydrothermal activity. These areas probably consist of the recent deposition of hydrothermal minerals in the MHV region. Based on the sub-bottom profiles in Fig.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003e, the boundary of the TZ-1 distribution is delineated.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e"},{"header":"8. Discussion","content":"\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e8.1 Relationship between Hydrothermal Activity and Seabed Structures\u003c/h2\u003e \u003cp\u003eThis study illustrates the interpretation of relevant features of hydrothermal activity in the MHV region, including hydrothermal vent distribution analyzed by chartered shipborne sonar and SSS water column imaging, as well as subsurface acoustic transparent zones, fluid channels, chimney structures, small normal faults, and fractures. Those features are superposed onto seabed topography and slope maps (Fig.\u0026nbsp;\u003cspan refid=\"Fig18\" class=\"InternalRef\"\u003e13\u003c/span\u003e). The results indicate that the hydrothermal activity in the MHV has occurred in its eastern and southwestern margins (Fig.\u0026nbsp;\u003cspan refid=\"Fig18\" class=\"InternalRef\"\u003e13\u003c/span\u003ea). The eastern region is the primary zone of hydrothermal activity, where numerous and widely distributed hydrothermal vents and distinct chimney structures exist in the seabed (Fig.\u0026nbsp;\u003cspan refid=\"Fig18\" class=\"InternalRef\"\u003e13\u003c/span\u003ea). In contrast, there are fewer hydrothermal activity features on the southwestern boundary (Fig.\u0026nbsp;\u003cspan refid=\"Fig18\" class=\"InternalRef\"\u003e13\u003c/span\u003ea).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn addition, based on the interpretation of the upper boundary of TZ-1 from sub-bottom profiles within the region, we can define the boundary of sediment subsidence in the near-seabed of the MHV (Fig.\u0026nbsp;\u003cspan refid=\"Fig18\" class=\"InternalRef\"\u003e13\u003c/span\u003eb). The distribution of minor normal faults or fractures near the seabed predominantly exists along the boundary of sediment subsidence (Fig.\u0026nbsp;\u003cspan refid=\"Fig18\" class=\"InternalRef\"\u003e13\u003c/span\u003eb). Furthermore, the distribution of fluid channels within the boundary of sediment subsidence makes it evident that regions with greater slope variations almost lack the presence of fluid channels (Fig.\u0026nbsp;\u003cspan refid=\"Fig18\" class=\"InternalRef\"\u003e13\u003c/span\u003eb). This suggests that the areas with the most significant terrain variations in and around MHV are closely related to the distribution zone of blanking zones observed in sub-bottom profiles (Fig.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003e). Through this analysis, the extent of collapses induced by hydrothermal activity in the near-seabed sediment layers of MHV is estimated to be an area of approximately 14 km\u0026sup2; (Fig.\u0026nbsp;\u003cspan refid=\"Fig18\" class=\"InternalRef\"\u003e13\u003c/span\u003eb). Additionally, using the southern dike of MHC on the northeast side of MHV as a natural boundary for near-seafloor hydrothermal activity within the study area, the sediment subsidence area between the boundary of subsidence and collapse is estimated to cover approximately 16 km\u0026sup2;.\u003c/p\u003e \u003cp\u003eBased on the analysis in Fig.\u0026nbsp;\u003cspan refid=\"Fig18\" class=\"InternalRef\"\u003e13\u003c/span\u003e, this study proposes that the region within the boundary of collapse is likely the earliest hydrothermal activity zone in the MHV. As deep-seated hydrothermal fluids migrated upwards and invaded surrounding sedimentary layers, the lower sedimentary layers gradually subsided. Eventually, if the upper layers cannot be sustained, significant collapses occur. The area between the boundary of collapse and subsidence is characterized by the formation of minor normal faults or fractures that were initially formed. These features intersect sedimentary layers, creating fluid channels that gradually spread outward, leading to slow subsidence of sedimentary layers. New minor normal faults or fracture systems are developing near the subsidence boundary. On the eastern side of MHV, sub-bottom profiles show the features of upward hydrothermal migration (Line01 in Fig.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003ed).\u003c/p\u003e \u003cp\u003eBased on the characteristics and the boundary of the seabed hydrothermal activities, this study suggests that the area of the potential hydrothermal mineral deposits in MHV is approximately 30 km\u0026sup2;, located within the limit of sediment subsidence zones. Hydrothermal mineral deposits are likely found in the seabed of the eastern side of MHV because of intense hydrothermal activity.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e8.2. Distribution of Recent Seabed Hydrothermal Activity in the MHV Region\u003c/h2\u003e \u003cp\u003eA comprehensive SSS image analysis shows hydrothermal vent activities are found in both the seabed and water column. Chimney structures observed in seabed profiles allow the identification of numerous seabed areas with hydrothermal potential (Fig.\u0026nbsp;\u003cspan refid=\"Fig19\" class=\"InternalRef\"\u003e14\u003c/span\u003e). Notably, the areas with chimney structures have been identified (marked with cyan stars in Fig.\u0026nbsp;\u003cspan refid=\"Fig19\" class=\"InternalRef\"\u003e14\u003c/span\u003e) on the eastern side of MHV (Fig.\u0026nbsp;\u003cspan refid=\"Fig19\" class=\"InternalRef\"\u003e14\u003c/span\u003e). These current seabed hydrothermal potential areas are distributed along the boundary of collapse zones (Fig.\u0026nbsp;\u003cspan refid=\"Fig19\" class=\"InternalRef\"\u003e14\u003c/span\u003e). This implies that after the collapse of the near-seabed layers, the migration path of the hydrothermal fluids is towards the seabed surface. The deep-seated hydrothermal fluid flows to seep out and weaken areas in terms of minor normal faults or fractures.\u003c/p\u003e\u003cp\u003eAdditionally, considering MHV as a center, it can be observed that the distribution width of the blanking zone in seabed profiles is more comprehensive to the west and narrower to the east. Similarly, the distribution width and thickness of the TZ-1 also exhibit a broader and thicker structure to the west and a narrower and thinner one to the east (Fig.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e12\u003c/span\u003e). Based on this, the early-stage hydrothermal activity on the seabed initially could develop towards the western side of MHV. As continuous hydrothermal activity-induced changes in the geological layers, the upward migration of deep-seated hydrothermal fluids gradually shifted towards the current eastern side of MHV.\u003c/p\u003e \u003c/div\u003e"},{"header":"9. Conclusion","content":"\u003cp\u003eHydrothermal activity has significantly developed in the MHV area. The sub-bottom profiler data can reveal acoustic transparent zones related to high-porosity sedimentary layers intruded by deep hydrothermal fluids. When the deep hydrothermal fluids have migrated upwards and diffused into surrounding strata, the shallow layers become gradually homogeneous and indistinguishable in the sub-bottom profiler data. Six transparent zones are identified in the sub-bottom profiles in the MHV area. The shallowest one in the seabed is labelled as TZ-1.\u003c/p\u003e \u003cp\u003eIn the area where the TZ-1 exists, the strata tend to tilt toward the summit of the MHV. The strata affected by hydrothermal fluid activity display gradual subsidence. This process could create minor normal faults or fractures, providing hydrothermal fluid channels to spread around the MHV. In regions where the blanking zone exists, the terrain shows morphological undulation due to the progressive weakening of the strata. Finally, large-scale sedimentary layer collapses occur. One collapse has caused the missing segment of the MHC dam in the northeast side of MHV.\u003c/p\u003e \u003cp\u003eHydrothermal activity in the western MHV has significantly decreased; no hydrothermal gas flare is found. In contrast, the SSS images and sub-bottom profiler data show numerous active hydrothermal vents and seabed chimney features in the eastern MHV. It suggests that the seabed hydrothermal activity is now active in the eastern side of the MHV. The east boundary of the hydrothermal fluid activity in the MHV region is between Line01 and Line02. Due to past hydrothermal activity, the western and southern sides of the MHV have experienced significant sedimentary subsidence or large-scale collapses. The collapse or subsidence of strata can be a signal indicating a decrease of hydrothermal activity.\u003c/p\u003e \u003cp\u003eBased on the analysis of bathymetric slope variations and the distribution of the TZ-1, blanking zone and fluid channels, we have identified the outline of the seabed collapses surrounding the MHV. The estimated area of the seabed collapses is approximately 14 km\u003csup\u003e2\u003c/sup\u003e. The strata collapse and subsidence are characteristic of the seabed influenced by hydrothermal activities. We estimate that the area of potential hydrothermal mineral deposits in the MHV seabed is approximately 30 km\u003csup\u003e2\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eChing-Hui Tsai, Shu-Kun Hsu, and Hsiao-Shan Lin were responsible for data processing, figure creation, and writing the manuscript.Song-Chuen Chen, Liwen Chen, Ching Hsu, and Lien-Kai Lin participated in discussions and provided suggestions.Chin-Wei Liang and Yen-Yu Cho assisted with data collection.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThis study was mainly supported by the Geological Survey and Mining Management Agency (GSMMA), the Ministry of Economic Affairs (MOEA), and the National Science and Technology Council, Taiwan. Part support was from the National Academy of Marine Research (NAMR) of the Ocean Affairs Council (OAC), Taiwan. We extend our gratitude to the crew of the R/V Legend, R/V Ocean Researcher I (OR1), and R/V New Ocean Researcher 2 (NOR2) for their invaluable assistance in data collection.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBaker, E. T., \u0026amp; German, C. R. (2004). On the global distribution of hydrothermal vent fields. In Mid-Ocean Ridges: Hydrothermal Interactions Between the Lithosphere and Oceans (pp. 245-266). American Geophysical Union.\u003c/li\u003e\n\u003cli\u003eBurguera, A., \u0026amp; Oliver, G. (2016). High-Resolution Underwater Mapping Using Side-Scan Sonar. PLOS ONE, 11(1), e0146396. https://doi.org/10.1371/journal.pone.0146396\u003c/li\u003e\n\u003cli\u003eButterfield, D. A., McDuff, R. E., Lilley, M. D., Lupton, J. E., \u0026amp; Massoth, G. J. (1994). Geochemistry of hydrothermal fluids from Axial Seamount hydrothermal emissions study vent field, Juan de Fuca Ridge: subseafloor boiling and subsequent fluid-rock interaction. Journal of Geophysical Research: Solid Earth, 99(B5), 9561-9594.\u003c/li\u003e\n\u003cli\u003eCann, J. R., Blackman, D. K., Smith, D. K., McAllister, E., Janssen, B., Mello, S., Pascoe, A. R., Avgerinos, E., \u0026amp; Escartin, J. (1997). Corrugated slip surfaces formed at North Atlantic ridge-transform intersections. Nature, 385(6614), 329-332.\u003c/li\u003e\n\u003cli\u003eChen, H. H., Chou, Y. C., Wang, C. C., Lin, Y. H., Lin, J. M., Liao, Y. C., Chen, S. C., Wei, C. Y., Chen, J. E., \u0026amp; Wang, Y. (2018). Seafloor Surveys using Deep-towed Vehicles for Mineral Resource Investigation off Taiwan.Paper presented at the OCEANS 2018 MTS/IEEE Charleston.\u003c/li\u003e\n\u003cli\u003eChen, T. T., Hsu, H. H., Su, C. C., Liu, C. S., Wang, Y., Chen, S. C., \u0026amp; Wu, S. F. (2023). Hydrothermal characteristics of the Mienhua submarine volcano in the southernmost Okinawa trough. Marine Geophysical Research, 44(2), 10.\u003c/li\u003e\n\u003cli\u003eChou, Y. C., Wang, C. C., Chen, H. H., \u0026amp; Lin, Y. H. (2019). Seafloor characterization in the southernmost Okinawa Trough from underwater optical imagery. Terrestrial, Atmospheric \u0026amp; Oceanic Sciences, 30(5).\u003c/li\u003e\n\u003cli\u003eCosta, P. M., Escart\u0026iacute;n, J., Tivey, M. A., Lin, J., \u0026amp; German, C. R. (2017). Submarine Volcanoes and Hydrothermal Systems. Geological Society Special Publication.\u003c/li\u003e\n\u003cli\u003eEdmond, J. M., Measures, C., McDuff, R. E., Chan, L. H., Collier, R., Grant, B., Gordon, J. B., \u0026amp; Corliss, J. B. (1979). Ridge crest hydrothermal activity and the balances of the major and minor elements in the ocean: the Galapagos data. Earth and Planetary Science Letters, 46(1), 1-18.\u003c/li\u003e\n\u003cli\u003eFabbri, O., Moni\u0026eacute;, P., \u0026amp; Fournier, M. (2004). Transtensional deformation at the junction between the Okinawa trough back-arc basin and the SW Japan island arc. Geological Society of London Special Publication, 227(1), 297-312.\u003c/li\u003e\n\u003cli\u003eGerman, C. R., \u0026amp; Von Damm, K. L. (2006). Hydrothermal processes. In Treatise on Geochemistry, 6, 181-222.\u003c/li\u003e\n\u003cli\u003eGermanovich, L. N., Ballu, V., \u0026amp; Bouguet, C. (2011). Geophysical and Hydrothermal Signatures of Submarine Vent Fields. Geophysical Research Letters, 38, L15302. doi:10.1029/2011GL048337.\u003c/li\u003e\n\u003cli\u003eGungor, A., Lee, G. H., Kim, H. J., Han, H. C., Kang, M. H., Kim, J., \u0026amp; Sunwoo, D. (2012). Structural characteristics of the northern Okinawa Trough and adjacent areas from regional seismic reflection data: geologic and tectonic implications. Tectonophysics, 522, 198-207.\u003c/li\u003e\n\u003cli\u003eHannington, M. D., Jonasson, I. R., Herzig, P. M., \u0026amp; Petersen, S. (1995). Physical and chemical processes of seafloor mineralization at mid-ocean ridges. Reviews of Geophysics, 33(2), 109-135.\u003c/li\u003e\n\u003cli\u003eHaymon, R., Fornari, D., Von Damm, K. L., Lilley, M., Perfit, M., Edmond, J., Shanks III, W. C., Lutz, R., Grebmeier, J., Carbotte, S. J. E., \u0026amp; Letters, P. S (1993). Volcanic eruption of the mid-ocean ridge along the East Pacific Rise crest at 9\u0026deg;45\u0026ndash;52\u0026rsquo;N: direct submersible observations of seafloor phenomena associated with an eruption event in April 1991. Earth and Planetary Science Letters, 119(1-2), 85-101.\u003c/li\u003e\n\u003cli\u003eHsu, F. H., Su, C. C., Lin, Y. S., Lee, H. F., Chu, M. F., Lan, T., Wu, S.-F., \u0026amp; Chen, S. C. (2024). Geochemical indications of hydrothermal fluid through sediments within the Geolin Mounds and Mienhua Volcano hydrothermal fields, southernmost Okinawa Trough. Deep Sea Research Part I: Oceanographic Research Papers, 207, 104293.\u003c/li\u003e\n\u003cli\u003eHsu, S. K., 2001. Lithospheric structure, buoyancy and coupling across the southernmost Ryukyu subduction zone: An example of decreasing plate coupling. Earth Planet. Sci. Lett., 186, 471-478.\u003c/li\u003e\n\u003cli\u003eHsu, S. K., Yeh, Y. C., Sibuet, J. C., Doo, W. B., \u0026amp; Tsai, C. H. (2013). A mega-splay fault system and tsunami hazard in the southern Ryukyu subduction zone. Earth and Planetary Science Letters, 362, 99\u0026ndash;107.\u003c/li\u003e\n\u003cli\u003eIfremer, Shom (2022). DORIS Software. SEANOE. https://doi.org/10.17882/90121\u003c/li\u003e\n\u003cli\u003eJohnson, H. P., \u0026amp; Holmes, M. L. (1989). Evolution and hydrothermal activity of the Juan de Fuca Ridge. Journal of Geophysical Research: Solid Earth, 94(B12), 15777-15792.\u003c/li\u003e\n\u003cli\u003eJuniper, S. K., \u0026amp; Sibuet, M. (1987). Vent fauna on an Eiffel Tower hydrothermal edifice on the Juan de Fuca Ridge. Marine Ecology Progress Series, 40, 65-73.\u003c/li\u003e\n\u003cli\u003eKase, M. (2010). Submarine Volcanism and Associated Hydrothermal Activity and Mineral Deposits. Tokyo University Press.\u003c/li\u003e\n\u003cli\u003eKelley, D. S., Karson, J. A., Früh-Green, G. L., Yoerger, D. R., Shank, T. M., Butterfield, D. A., Hayes, J. M., Schrenk, M. O., Olson, E. J., Proskurowski, G., Jakuba, M., Bradley, A., Larson, B., Ludwig, K., Glickson, D., Buckman, K., Bradley, A. S., Brazelton, W. J., Roe, K., Elend, M. J., Delacour, A., Bernasconi, S. M., Lilley, M. D., Baross, J. A., Summons, R. E., \u0026amp; Sylva, S. P. (2005). A serpentinite-hosted ecosystem: the Lost City hydrothermal field. Science, 307(5714), 1428-1434.\u003c/li\u003e\n\u003cli\u003eKimura, M. (1985). Back-arc rifting in the Okinawa Trough. Marine and Petroleum Geology, 2(3), 222\u0026ndash;240.\u003c/li\u003e\n\u003cli\u003eKodaira, S., Iwasaki, T., Urabe, T., Kanazawa, T., Egloff, F., Makris, J., \u0026amp; Shimamura, H. (1996). Crustal structure across the middle Ryukyu trench obtained from ocean bottom seismographic data. Tectonophysics, 263(1-4), 39\u0026ndash;60.\u003c/li\u003e\n\u003cli\u003eLee, C. S., Shor, G. G., Bibee, L. D., Lu, R. S., \u0026amp; Hilde, T. (1980). Okinawa Trough: Origin of a back-arc basin. Marine Geology, 35, 219\u0026ndash;241.\u003c/li\u003e\n\u003cli\u003eLetouzey, J., \u0026amp; Kimura, M. (1986). The Okinawa Trough: genesis of a back-arc basin developing along a continental margin. Tectonophysics, 125(1\u0026ndash;3), 209\u0026ndash;230.\u003c/li\u003e\n\u003cli\u003eLin, Y. C., Lin, J. Y., Hsu, S. K., Chen, S. C., Lin, S. S., \u0026amp; Tsai, C. H. (2024). Gas emission characteristics and tectonic implications in the southernmost Okinawa Trough from split‐beam echo sounder observations. Journal of Geophysical Research: Oceans, 129(3), e2023JC020176.\u003c/li\u003e\n\u003cli\u003eMassoth, G. J., Milburn, H. B., Hammond, S. R., Butterfield, D. A., McDuff, R. E., \u0026amp; Lupton, J. E. (1988). The geochemistry of submarine venting fluids at Axial Volcano, Juan de Fuca Ridge: New sampling methods and a VENTS program rationale. In Global venting, midwater, and benthic ecological processes (Vol. 84, pp. 29-59). NOAA Rockville, MD.\u003c/li\u003e\n\u003cli\u003eMcMullen, K. Y., Poppe, L. J., Ackerman, S. D., Blackwood, D. S., Lewit, P. G., \u0026amp; Parker, C. E. (2013). Sea-Floor Geology in Northeastern Block Island Sound, Rhode Island (No. 2013-1003). US Geological Survey.\u003c/li\u003e\n\u003cli\u003eMorton, B. R., Taylor, G. I., \u0026amp; Turner, J. S. (1956). Turbulent gravitational convection from maintained and instantaneous sources. Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, 234(1196), 1-23.\u003c/li\u003e\n\u003cli\u003ePoncelet, C., Billant, G., Corre, M.-P., \u0026amp; Saunier, A. (2024). Globe (GLobal Oceanographic Bathymetry Explorer) Software. SEANOE. https://doi.org/10.17882/70460\u003c/li\u003e\n\u003cli\u003eSavini, A. (2011). Side-Scan Sonar as a Tool for Seafloor Imagery: Examples from the Mediterranean Continental Margin. In Sonar Systems. InTech. http://dx.doi.org/10.5772/18375\u003c/li\u003e\n\u003cli\u003eShinjo, R., Chung, S. L., Kato, Y., \u0026amp; Kimura, M. (1999). Geochemical and Sr-Nd isotopic characteristics of volcanic rocks from the Okinawa Trough and Ryukyu Arc: implications for the evolution of a young, intracontinental back arc basin. Journal of Geophysical Research: Solid Earth, 104, 10591\u0026ndash;10608.\u003c/li\u003e\n\u003cli\u003eSibuet, J. C., Deffontaines, B., Hsu, S.-K., Thareau, N., LeFormal, J. P., Liu, C.-H., \u0026amp; Party, A. (1998). Okinawa Trough backarc basin: early tectonic and magmatic evolution. Journal of Geophysical Research: Solid Earth, 103, 30245\u0026ndash;30267.\u003c/li\u003e\n\u003cli\u003eSibuet, J. C., Hsu, S. K., Shyu, C. T., \u0026amp; Liu, C. S. (1995). Structural and kinematic evolutions of the Okinawa Trough backarc basin. Backarc basins: Tectonics and magmatism, 343-379.\u003c/li\u003e\n\u003cli\u003eSibuet, J. C., Letouzey, J., Barrier, F., Charvet, J., Foucher, J. P., Hilde, T. W. C., Kimura, M., Chiao, L.-Y., Marsset, B., Muller, C., \u0026amp; Stephan, J. F. (1987). Back arc extension in the Okinawa trough. Journal of Geophysical Research, 92, 14041\u0026ndash;14063.\u003c/li\u003e\n\u003cli\u003eSingh, H., Shank, T., \u0026amp; Fornari, D. (2012). Hydrothermal Vent Geomorphology and the Influence of Geological Processes on Vent Communities. Oceanography, 25(1), 44-53. doi:10.5670/oceanog.2012.15.\u003c/li\u003e\n\u003cli\u003eSinquin, J. M., Lurton, X., Vrignaud, C., Mathieu, G., \u0026amp; Bisquay, H. (2016). DORIS Software: New Tool to Process Sound Velocity Profiles. Hydro International, 20, 22-25.\u003c/li\u003e\n\u003cli\u003eStoffers, P., Worthington, T. J., Hekinian, R., \u0026amp; Shipboard Scientific Party (1994). Hydrothermal activity and its influence on sedimentation in the Manus Basin. Marine Geology, 116(1-2), 51-82.\u003c/li\u003e\n\u003cli\u003eTivey, M. K., Humphris, S. E., Thompson, G., Hannington, M. D., \u0026amp; Rona, P. A. (1995). Deducing patterns of fluid flow and mixing within the TAG active hydrothermal mound using mineralogical and geochemical data. Journal of Geophysical Research: Solid Earth, 100(B7), 12527-12555.\u003c/li\u003e\n\u003cli\u003eTsai, C. H., Hsu, S. K., Chen, Y. F., Lin, H. S., Wang, S. Y., Chen, S. C., \u0026amp; Cho, Y. Y. (2019). Gas plumes and near-seafloor bottom current speeds of the southernmost Okinawa Trough were determined by echo sounders. Terrestrial, Atmospheric \u0026amp; Oceanic Sciences, 30(5).\u003c/li\u003e\n\u003cli\u003eTsai, C. H., Hsu, S. K., Chen, S. C., Wang, S. Y., Lin, L. K., Huang, P. C., Chen, K. T., Lin, H. S., Liang, C. W., \u0026amp; Cho, Y. Y. (2021). Active tectonics and volcanism in the southernmost Okinawa Trough back-arc basin derived from deep-towed sonar surveys. Tectonophysics, 817, 229047. https://doi.org/10.1016/j.tecto.2021.229047.\u003c/li\u003e\n\u003cli\u003eTunnicliffe, V., Juniper, S. K., \u0026amp; Sibuet, M. (2003). Reducing environments of the deep-sea floor. Oceanography and Marine Biology: An Annual Review, 41, 1-44.\u003c/li\u003e\n\u003cli\u003eUmbgrove, J. H. F. (1950). Studies on Submarine Volcanoes. Springer.\u003c/li\u003e\n\u003cli\u003eVon Damm, K. L. (1990). Seafloor hydrothermal activity: black smoker chemistry and chimneys. Annual Review of Earth and Planetary Sciences, 18(1), 173-204.\u003c/li\u003e\n\u003cli\u003eWhite, R. S. (2005). Submarine Volcanism and Hydrothermal Activity. Marine Geology. 215(1-2), 7-20.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 and 2 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"terrestrial-atmospheric-and-oceanic-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"taoj","sideBox":"Learn more about [Terrestrial, Atmospheric and Oceanic Sciences](https://link.springer.com/journal/44195)","snPcode":"44195","submissionUrl":"https://submission.springernature.com/new-submission/44195/3","title":"Terrestrial, Atmospheric and Oceanic Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Open","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"southern Okinawa Trough, Mienhua submarine volcano, hydrothermal Activity, side-scan sonar, sub-bottom profiler, hydrothermal flare, chimney","lastPublishedDoi":"10.21203/rs.3.rs-4913834/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4913834/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eHydrothermal vents can be detected using echo sounders. Here, we employed a deep-tow side-scan sonar and sub-bottom profiler to analyze the seabed features associated with hydrothermal activity near the Mienhua submarine volcano (MHV). The MHV is located in the northern margin of the southern Okinawa Trough back-arc basin. Our deep-tow sub-bottom profiler data show an upward hydrothermal fluid activity in the seabed, confirming the active hydrothermal circulation around the MHV. Widespread acoustic transparent zones are found in the upper strata, ascribed to the intrusion of hydrothermal fluid into high porosity sediment layers. In the area where acoustic transparent zones exist, the strata tilt towards the summit of the MHV. The strata influenced by the intrusion of hydrothermal fluids may create minor normal faults or fractures. These faults provide new hydrothermal fluid pathways to spread outwards. The weakened upper strata due to the hydrothermal fluids may finally collapse because of the gravity instability. The hydrothermal activity in the western portion of the MHV is no longer active. In contrast, the hydrothermal activity in the eastern portion of the MHV is rigorous and is associated with the widespread hydrothermal vents, gas flares and chimneys. The area of potential hydrothermal mineralization near the seabed of the MHV is estimated to be ~30 km².\u003c/p\u003e","manuscriptTitle":"Hydrothermal Activity around the Mienhua submarine volcano in the northern margin of the Southern Okinawa Trough","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-10-11 07:04:34","doi":"10.21203/rs.3.rs-4913834/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-10-17T15:17:50+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-10-17T14:53:15+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-10-07T10:16:12+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"121536928936580633977614207671667016071","date":"2024-09-16T01:40:28+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"66447272661169694772402996389342561276","date":"2024-09-14T08:22:34+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-09-14T06:05:32+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-08-14T14:33:46+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-08-14T14:33:23+00:00","index":"","fulltext":""},{"type":"submitted","content":"Terrestrial, Atmospheric and Oceanic Sciences","date":"2024-08-14T13:02:56+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"terrestrial-atmospheric-and-oceanic-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"taoj","sideBox":"Learn more about [Terrestrial, Atmospheric and Oceanic Sciences](https://link.springer.com/journal/44195)","snPcode":"44195","submissionUrl":"https://submission.springernature.com/new-submission/44195/3","title":"Terrestrial, Atmospheric and Oceanic Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Open","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f113ba27-817c-4f2a-a07e-095068f271f9","owner":[],"postedDate":"October 11th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-05-31T11:23:15+00:00","versionOfRecord":[],"versionCreatedAt":"2024-10-11 07:04:34","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4913834","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4913834","identity":"rs-4913834","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}