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The western continental margin of India and the adjacent deep ocean basins were formed by break-up and separation among India, Seychelles and Madagascar since the Late Cretaceous. The initial India-Madagascar separation and the subsequent India-Seychelles separation are believed to have been caused by the Marion hotspot at ~90 Ma and the Reunion hotspot at ~68.5 Ma, respectively. These geodynamic events resulted in the formation of several bathymetric highs that probably represent imprints of these volcanic events. In the present study these bathymetric high features were mapped comprehensively to understand their morphotectonic characteristics, using a fresh set of multibeam bathymetry, sea-surface gravity and magnetic anomalies, complemented by the available multichannel seismic reflection sections. A high-resolution bathymetric map of the southwestern continental margin of India and the adjoining deep offshore regions has been generated to decipher detailed morphological configuration and distribution of prominent undersea bathymetric features. We also carried out detailed morphometric analysis of these features to deduce the morphological parameters. A total of 33 individual bathymetric high features were identified and classified as seamounts, hills, knolls, guyots and plateaus based on the standardization of undersea feature names published by Intergovernmental Oceanographic Commission (IOC) and International Hydrographic Organization (IHO) in 2013. Multichannel seismic reflection, sea-surface gravity and magnetic data were used to describe the sub-seafloor configuration and qualitative interpretation of the geophysical signatures associated with the bathymetric highs. Interpretation of the multichannel seismic reflection sections suggest that some of these identified features are extrusive in nature, while others are intrusive. These features are associated with characteristic gravity highs superimposed over regional negative anomalies and complex negative and positive magnetic anomalies. The study results suggest that the genesis of the bathymetric highs mapped in the study area could be attributed to the hotspot volcanism, caused by the Marion or Reunion hotspots. We infer that the features in the southwestern continental margin of India closer to the Alleppey-Trivandrum Terrace Complex might have been created by the Marion hotspot volcanism, while those in the Laccadive Basin and eastern sector of the Laccadive Plateau might have been formed by Reunion hotspot volcanism.

In this paper, we investigate the wave attenuation by mangroves using modified 2D Nonlinear Shallow Water Equations. Numerically, we solve the model using a staggered finite volume method that is free from damping error. Further, several benchmark tests are performed to show the robustness of our numerical model. Then, we implement our numerical model to investigate the effects of mangroves in the wave attenuation caused by tsunamis in Manila Bay. The bathymetry profile of Manila Bay used in this study is obtained from the General Bathymetric Chart of the Oceans (GEBCO). Numerical results show that the presence of mangroves can reduce ocean waves near the coast. Simulations on varying density and width of mangrove forest quantify how much the tsunami wave height can be reduced. The results of this work may guide the policymakers of the Philippines in deciding the best strategy in rehabilitating Manila Bay.

An extensive system of tidal channels, starting with Jinshan Trough in the east, is located along the north shore of Hangzhou Bay, China. This contribution investigates the morphological evolution of Jinshan Trough by using 17 bathymetric charts from a series covering a period of 51 years from 1960 to 2011. Three stages of evolution during this period are distinguishable based on the morphology and annual mean volume data. The first stage (1960–1987) is characterized by extension of the trough; the second stage (1987–1996) is a relatively stable period with some adjustments in the trough morphology; the third stage (1996–2011) is marked by the processes of erosion and deposition in the beginning of the period and a subsequent slow erosion process. Spatio-temporal variability of the trough was evaluated by using empirical orthogonal function (EOF) analysis. The first eigenfunction indicates that erosion is the main evolution process and there exists three stages similar to those distinguished from volume variations. The second eigenfunction mainly reflects erosion and deposition in the northwest part of the trough located in the flood tidal current shadow area of the artificial headland in Jinshan. The third eigenfunction mainly reflects annual fluctuations of erosion and deposition in the side slope at the artificial headland in Jinshan. A particularly intense erosion process occurred between 1996 and 1998. The major effects on morphological evolution in Jinshan Trough from 1960 to 2011 were investigated and tentative conclusions were presented. Continuous coastal reclamations in Jinshan had the most pronounced effect on the morphological evolution during the first and the second stages. The storm surge had a pronounced effect on the evolution at the beginning of the third stage.

Mapping bathymetric change is a core task for a wide range of navigation, research, monitoring, and design applications. Satellite-derived bathymetry (SDB) can support this activity, particularly when using data from a platform, like the Sentinel-2A/B twin mission of the Copernicus programme, which provides routine and repetitive image acquisition at 10 m spatial resolution. As a result, SDB can expand on the temporal and spatial scope of more conventional mapping methods, such as lidar (or multi-beam). In this study, we use SDB, in comparison with high-resolution airborne lidar bathymetry (ALB), to quantify bathymetric changes at two inlets in North Carolina following the impacts of the devastating Hurricane Florence in September 2018. A recently developed multi-temporal SDB model that overcomes problems associated with turbidity and noise effects (whitecaps, ships, cloud shadows, etc.) is used with Sentinel-2 imagery. We identify bathymetric changes in shallow areas with navigation channels in two of the most dynamic inlets in the Outer Banks, Oregon and Hatteras. Multiple lidar surveys are used to validate the SDB method and for an assessment of accuracy and vertical uncertainty. The multi-temporal SDB products and ALB both show similar results in the erosion/accretion patterns. Comparing the change determined from the two methods, gives a median absolute error of ~0.5 m of SDB compared with ALB, with bias of ±0.2 m for depths ≤7 m; errors that are equivalent to those associated with the SDB estimated absolute depths. The composited SDB yields greater spatial coverage than lidar because it can retrieve data in areas where the lidar mission may have been constrained by turbidity or surf, and also because of the 300-km swath width. The Sentinel-2 constellation provides five-day revisit at the equator (more frequent at higher latitudes), allowing rapid construction of a bathymetric map as well as developing an archive for retrospective analysis. By implementing the multi-temporal turbidity correction, SDB based on Sentinel-2 may substantially enhance existing survey methods for change detection and support operational and recursive coastal monitoring on local to regional scales., This research was supported by the Sen2Coast Project (RTI 2018-098784-J-I00) funded by the Spanish Ministry of Science, Innovation and Universities (MCIU), the Spanish State Research Agency (AEI) and the European Regional Development Fund (ERDF). Support was also provided by the National Oceanic and Atmospheric Administration (NOAA).

In a recent paper, Ve et al. (2021) present sediment budget and morphological change in the Red River Delta under increasing human interferences. However, there are some fundamental flaws associated with applying kriging interpolation technique, sequential bathymetric charts and assessing elevation change between subsequent bathymetric surveys. In addition, their approach to calculating sediment budget is also inaccuracy caused by unreliable inferences. Consequently, their results contradict our current understanding of the Red River sediment dispersal system.

Shallow coastal areas of oceans, seas and lakes pose significant remote sensing and navigational challenges due to the transient nature of bathymetric features that characterize these areas (e.g., shoals and shoaling). Seabed data/maps often represent these areas as “white ribbon” zones, where sparse data coverage presents a particular challenge to defining and enforcing sustainable use of marine resources. Given the lengthy perimeter of coastlines, there is a need for cost-efficient methods for producing high resolution maps of shallow areas. The research described here compares airborne light detection and ranging (LiDAR) with shipboard acoustic surveys around the Kvarken Archipelago of the northern Baltic Sea. The Kvarken Archipelago includes a unique, brackish shallow water marine environment with a number of moraines. The landscape of the area is characterised by fields of ridged, washboard-like De Geer moraines. The moraines combined with an ongoing glacio-isostatic uplift typical of the area, lead into succession of the elevated structures from the seafloor to land, where present seabed structures will rise on land in future. The ongoing modification of the environment by both climatic and geologic forces contributes to complex geomorphic and ecological feedback systems operating on a range of spatial and temporal scales. Airborne LiDAR can provide high resolution remote sensing data on shallow coastal areas. The technology is especially effective in areas with very shoal waters, like those found along the Finnish coast. LiDAR enables continuous detection of topographic (elevation) and bathymetric (depth) data and can thus generate continuous maps of transition zones between continental and marine areas. Environmental conditions such as water clarity and ice cover can affect LiDAR depth detection capabilities; these conditions require complementary accuracy assessment strategies. As LiDAR cannot determine detailed information on seafloor surface substrate, and anything on subsurface substrate type, geological conditions are determined through the application of acoustic-seismic methods, sediment sampling and underwater video. Data from LiDAR surveys provide a detailed topographic and bathymetric map of the study area up to water depths of 14 m. The seabed bathymetry model shows a series of elevated, narrow, elongate features that appear throughout the study area. These parallel ridges represent the uppermost geomorphic features of the seafloor. Interpretation of acoustic bathymetric surveys indicates that these ridges are De Geer moraines. The general orientation of these moraines differs from that associated with older features of the northern Kvarken Archipelago. Eroded remnants of older De Geer moraines are overprinted at a high angle by the younger landforms. De Geer moraines in the study area thus represent two phases of deglaciation and finally the eastward ice-sheet/ice edge retreat. The combined approach of using LiDAR and acoustic bathymetric data provides new insights into past glacial dynamics of the Kvarken Archipelago and the Gulf of Bothnia.

The marine geophysical investigations carried out in the Eastern Arabian Sea revealed the presence of a bathymetric high feature, referred to as the Sagar Kanya Seamount. The preliminary morphology and geophysical characteristics of this feature were studied along a single transect by earlier researchers, however, a detailed geophysical mapping over the entire extent of this feature is still awaited. The present study aims for such a detailed investigation on the Sagar Kanya Seamount and its adjacent regions using newly acquired high-resolution multibeam bathymetry data, complemented with sea surface magnetic and gravity data. Bathymetric map reveals the presence of well-defined bathymetric high features constituting three seamounts connected with structural high/ridge-like features, together representing a large nearly elliptical bathymetric high complex surrounding a region of nearly flat seafloor, referred to as the Sagar Kanya Bathymetric High Complex (SKBHC). The overall morphology of this feature closely resembles with the shape of a submarine volcanic caldera. The gravity anomalies over this feature are mostly correlatable with topography; elliptical-shaped gravity highs are associated with bathymetric highs and gravity lows are associated with the enclosed flat seafloor. Some magnetic anomalies observed over the SKBHC are correlatable with the topographic highs, while others are observed over the flat seafloor. The magnetic anomalies are interpreted as features of post-caldera volcanism. In view of the proximity of this feature to the Reunion hotspot track, and the tectonic framework of the region, the genesis of the SKBHC is attributed to the Reunion hotspot volcanism.

Five small islands offshore of the State of Kuwait in the northern Arabian Gulf (Miskan, Awhah, Kubbar, Qaruh, and Umm Al-Maradem) occur in differing structural settings and have evolved in a dynamic environment of shifting fluvial depocenters, fluctuating Holocene sea level, and variable tidal conditions. As a first step in reconstructing the origin and evolution of the islands, bathymetric charts, historical photographs, topographic profiles, and sediment samples were used to investigate their geomorphology and sedimentary environments. The subaerial portion of the islands varies in area from 0.04 to 0.57 km2. The plan-shape ellipticity ranges from nearly circular (0.10) to oval-shaped (0.54). The northern two islands (Miskan and Awhah) experience mesotidal conditions and are situated on a shallow platform (

Sea-level fluctuations are a dominant mechanism that control coastal environmental changes through time. This is especially the case for the successive regressions and transgressions over the last interglacial cycle, which have shaped the deposition, preservation and erosion patterns of unconsolidated sediments currently submerged on continental shelves. The current study focuses on creating an integrated marine and terrestrial geophysical and litho-stratigraphic framework of the coastal zone of Hadera, north-central Israel. This research presents a case study, investigating the changing sedimentological units in the study area. Analysis suggest these represent various coastal environments and were deposited during times of lower than present sea level and during the later stages of the Holocene transgression. A multi-disciplinary approach was applied by compiling existing elevation raster grids, bathymetric charts, one hundred lithological borehole data-sets, and a 110 km-long sub-bottom geophysical survey. Based on seismic stratigraphic analysis, observed geometries, and reflective appearances, six bounding surfaces and seven seismic units were identified and characterized. These seismic units have been correlated with the available borehole data to produce a chronologically constrained lithostratigraphy for the area. This approach allowed us to propose a relationship between the lithological units and sea-level change and thus enable the reconstruction of Hadera coastal evolution over the last ~ 100 ka. This reconstruction suggests that the stratigraphy is dominated by lowstand aeolian and fluvial terrestrial environments, subsequently transgressed during the Holocene. The results of this study provide a valuable framework for future national strategic shallow-water infrastructure construction and also for the possible locations of past human settlements in relation to coastal evolution through time.

Using bathymetry and altimetric gravity anomalies, a 1° × 1° lithospheric effective elastic thickness (T e) model over the Louisville Ridge and its adjacent regions is calculated using the moving window admittance technique. For comparison, three bathymetry models are used: general bathymetric charts of the oceans, SIO V15.1, and BAT_VGG. The results show that BAT_VGG is more suitable for calculating T e than the other two models. T e along the Louisville Ridge was re-evaluated. The southeast of the ridge has a medium T e of 10–20 km, while T e increases dramatically seaward of the Tonga-Kermadec trench as a result of the collision of the Pacific and Indo-Australian plates.

Bathymetric echosounder mapping and seafloor observations using a remotely operated vehicle were conducted on the Miyako-Sone platform, located northeast of Miyako-jima, Ryukyu Islands, northwestern Pacific Ocean. This study aims to unravel the origin and development of the Miyako-Sone platform, a key field to reconstruct the biogeographic evolution and the geologic history of the Ryukyu Islands. The resulting high-resolution bathymetric map reveals details of the seafloor geomorphology, including the spatial distribution of submerged terraces on the platform. We report herein the discovery of a submerged reef (the Miyako-Sone reef) on the platform whose top is at a water depth of 56 m, extending in a north–south direction for up to 1 km and with a minimum width of 500 m. The reef consists of a central depression and a concentric marginal ridge; topographic features analogous to “spurs and grooves” are recognized along the outer margin of the marginal ridge. The Miyako-Sone reef was drowned during a period of global postglacial sea-level rise between ~ 11–12 ka which may coincide with MWP-1B at ~ 11.5 ka. The increase in sea surface temperature in the Ryukyu Islands at ~ 11 ka shows that the Miyako-Sone reef formed during the final stage of the cooler postglacial period. Part of the Miyako-Sone platform was likely a land bridge for the migration of terrestrial organisms from Okinawa-jima to Miyako-jima during low sea-level stands after the deposition of the Ryukyu Group.

Long period magnetotelluric (LMT) data are generally used as the prime tool to shed light on the conductivity of the deep crust and upper mantle structure. Naturally, LMT data are sensitive to the influence of highly conductive bodies even at far distances. Sea water constitutes the main widespread electrical conductor at shallow levels of the Earth's crust. Its low resistivity values, around 0.25 Ωm, contrast sharply with most geological structures of solid earth. Consequently, the presence of irregular continental borders and varying bathymetries significantly influences LMT parameter, such as phase tensor and tipper vectors. This effect is especially important in areas where large and small oceans are connected by narrow gateways. The Gibraltar Strait (southern Spain) connects the vast Atlantic Ocean with the irregular and relatively small Mediterranean Sea. Several 3D models have been developed in the region nearby the Strait, some featuring a roughly simplified geological structure, to show the influence of seawater on tipper and phase tensor. Here, detailed bathymetry (General Bathymetric Chart of the Oceans, GEBCO) including the coastline is considered in a model that enables us to analyze the influence of the Strait of Gibraltar on LMT data. We stress the significance of the Sea for LMT data interpretation and the development of 3D conductivity models, especially in regions involving complex coastline geometries and bathymetry near narrow straits. Forward modeling studies are essential to accurately appraise the sea influence, which may mask 3D geological structures.

The results of a numerical assessment of the wave energy in the Iberian North and West coast are presented. The implemented system uses the WAVEWATCH III model for wave generation and swell propagation, covering the entire North Atlantic basin, and the SWAN model for wave generation and propagation in the coastal areas. WAVEWATCH III provides the wave boundary conditions for the areas simulated by SWAN, which in turn provides the boundary conditions for the high resolution areas. Although there are results available for the Portuguese west coast and Spanish northwestern coast, they use different approaches and wind forcing data, and the present paper presents a consistent approach to identify differences among the various areas, by modelling them with the same models and using the same wind forcing and parameterizations of the SWAN model. The wind fields used in both models are from Era-Interim, a global atmospheric reanalysis data set produced by the European Centre for Medium-Range Weather Forecasts and the bathymetry used in high resolution areas are from the General Bathymetric Chart of the Oceans. The model results are validated with various buoy's significant wave height, mean wave period and mean wave direction. Results are presented of the average wave power spatial distribution in the coarse SWAN domain for each month of the three years, and for the high resolution areas the spatial distribution wave energy is provided for winter and summer.

We investigated submerged ruins from the 1923 Nebukawa landslide, which was caused by the 1923 Kanto earthquake. The on-land areas affected by the landslide have been restored and evidence of the landslide is mostly gone, but huge structures that appear to be man-made have been observed by divers on the seafloor near the area of the landslide. We used a fish finder designed for leisure use and other low-cost equipment to conduct a marine acoustic survey. Because the affected area off Nebukawa is close to shore and shallow and the tools were sufficiently lightweight, we were able to use an inflatable raft for the survey. We created a bathymetric map and side-scan images showing features of the landslide mass and scattered huge structures exposed on the seafloor. After the acoustic investigations, we conducted a diving investigation and were able to ascertain that the structures were made of concrete and were most likely parts of the old Nebukawa station. The ruins were displaced about 260 to 320 m horizontally from the original station location (to 110–170 m offshore) and were mixed with coarse rock fragments from the landslide mass. The distribution of bottom materials suggests that the landslide struck the seafloor and then traveled as far as 460 m offshore from the coastline. The landslide had an equivalent coefficient of friction (H/L) of about 0.15, indicating high mobility. The landslide probably transformed into a turbulent flow mixed with basal sandy sediments, which propelled the debris farther offshore.

A new high resolution bathymetric map of the Levant Basin between Israel and the Eratosthenes Seamount reveals previously undetected folds, faults and channels. The map facilitates a regional map-view analysis of structures that were previously examined only in cross section. The systematic mapping of morpho-structural elements in the entire basin is followed by a kinematic interpretation that distinguished between two main processes sculpting the seabed from bottom and top: salt tectonics and sediment transport. We show that the contractional domain related to salt tectonics is far more complex than previously thought. Ridges, previously interpreted as contractional folds are, in fact, surficial undulations of the seabed reminiscent of sediment waves. Moreover, other folds previously interpreted as downdip contraction of the westward gliding Plio-Quaternary section are, in some parts of the basin, caused by updip climbing of this section eastwards as a result of the regional pattern of salt flow away from the Nile Cone. In the context of sediment transport, we show that the northern Sinai continental slope is covered by a dense net of turbidite channels, whereas the Levant slope has no channels at all. Particularly interesting is the Levant Turbidite Channel, described and named here for the first time. This feature begins at the southeastern corner of the Mediterranean at water depths of ~ 1100 m, continues along the valley between the Sinai and Levant slopes, and reaches the deepest part of the basin, in water depths of ~ 2500 m, northeast of the Eratosthenes seamount. However, this prominent feature cannot be explained by the current drainage, consisting of two minor rivers that enter the basin at that point, and thus most likely reflects periods of wetter climate and/or lower sea-level, when these rivers were more active and possibly connected to the submarine channel system.

High-resolution and high-density 2-D multichannel seismic data, combined with high-precision multibeam bathymetric map, are utilized to investigate the characteristics and distribution of submarine landslides in the middle of the northern continental slope, South China Sea. In the region, a series of 19 downslope-extending submarine canyons are developed. The canyons are kilometers apart, and separated by inter-canyon sedimentary ridges. Numerous submarine landslides, bounded by headscarps and basal glide surfaces, are identified on the seismic profiles by their distorted to chaotic reflections. Listric faults and rotational blocks in head areas and compressional folds and inverse faults at the toes of the landslides are possibly developed. Three types of submarine landslides, i.e., creeps, slumps, and landslide complexes, are recognized. These landslides are mostly distributed in the head areas and on the flanks of the canyons. As the most widespread landslides in the region, creeps are usually composed of multiple laterally-coalesced creep bodies, in which the boundaries of singular component creep bodies are difficult to delineate. In addition, a total of 77 landslides are defined, including 61 singular slumps and 16 landslide complexes that consist of two or more component landslides. Statistics show that most landslides are of a small dimension (0.53–18.09 km² in area) and a short runout distance (less than 3.5 km). Regional and local slope gradients and rheological behavior of the displaced materials might play important roles in the generation and distribution of the submarine landslides. A conceptual model for the co-evolution of the canyons and the associated landslides in the study area is presented. In the model it is assumed that the canyons are initiated from gullies created by landslides on steeper sites of the continental slope. The nascent canyons would then experience successive retrogressive landsliding events to extend upslope; at the same time canyon downcutting or incision would steepen the canyon walls to induce more landslides.

A comprehensive inventory of High Arctic cross-shelf troughs is compiled from International Bathymetric Chart of the Arctic Ocean (IBCAO) bathymetric data (v. 3.0). The location of 75 cross-shelf troughs is presented alongside a synthesis of their key physiographic characteristics and available glacial-geological evidence. The troughs are interpreted to have been occupied intermittently and eroded by marine-terminating ice streams that traversed the shelf during at least one, and often many Quaternary full-glacial periods. Considerable variation in cross-shelf trough physiography exists in the High Arctic; trough lengths range between 35 and 1400 km, widths from 12 to 260 km, and maximum depths from 200 to 1000 m. The longest cross-shelf troughs extend through inter-island channels on the Beaufort Sea, Queen Elizabeth Islands and Barents–Kara Sea margins. The gradient of the upper-slope beyond High Arctic glacial troughs, which ranges between 0.3° and 13°, is shown to have a negative relationship with palaeo-ice stream drainage basin area and trough length. Glacial-sedimentary depocentres or trough-mouth fans (TMFs) are inferred on the basis of bathymetric and, where available, seismic evidence, to exist beyond the majority of High Arctic cross-shelf troughs. Evidence of shelf progradation or TMF development is absent from the slope beyond several High Arctic troughs, probably as a result of limited sediment supply to the margin and/or sediment by-passing of the upper-slope. On the South Greenland continental margin, it is likely that steep slopes prevented the development of significant glacial-sedimentary depocentres beyond cross-shelf troughs or that glacigenic debris has been removed from the upper-slope by submarine slope failure.

Bathymetry is the science of measuring and charting the depths to determine the topography of the seafloor and other bodies of water. It has several important practical and academic applications. For this reason, having computational tools capable of analyzing bathymetric charts would be useful for domain experts studying the various problems related to water depth. Data mining is a well known technique for extracting information from large datasets, but cannot be directly applied to images. The contribution of this work is an approach for using data mining in bathymetry images. We propose a method for processing input images, in order to extract records and their features, which can be processed by classic data mining algorithms. Additionally, we also propose techniques to visualize both data mining results and map characteristics. For evaluation purposes, the proposed approach was applied to a cold-water corals dataset, in order to predict where corals are likely to be found, under a domain expert supervision.

The basin of Lake Kotokel, located along the eastern shore of Lake Baikal, Russia, has attracted several scientific projects to investigate the climate, vegetation and lake history throughout the Late Pleistocene and Holocene. However, little was known about its basin structure and sediment architecture. Echo sounding and 3.5 kHz single frequency sub-bottom profiling were used to decipher the basin morphology and seismic stratigraphy to a depth of approximately 50 m. The bathymetric map shows a very shallow lake of 4 m mean water depth and an almost flat lake bottom. A distinct elongated small-sized depression of up to 12 m water depth between the north-western coast and a small island developed along an NW-SE-oriented fault line. A total of 46 km of seismic profiles crossing the lake along 12 transects shows that the bottom sediments consist of three different facies, which accords to previously analyzed core sequences. Several distortions of sediment layers at various sites indicate tectonically induced impact, which resulted in up to 3 m vertical offsets of sediment packages at local sites. The offsets indicate a probably still active fault along the western shoreline of the lake. Soft gyttja of the upper 6 m does not show distortions and may have obscured potential younger tectonic activity. The sediments date to the Late Pleistocene. Small updoming features along the boundary between layers I and II may be assigned to degassing processes or to seismic activity. River channel fills along the north-eastern coast are indicative of a lower lake level prior to 15 ka BP. The sediment stratigraphy indicates that suitable coring sites for paleoclimate studies are only located in the southern part of the basin where almost undisturbed sediments can be expected.

An 8 km 2 area representative of deep offshore basins in Lake Superior was surveyed with multi-beam sonar and a high-frequency seismic-reflection system to create a high-resolution bathymetric map of the lake floor morphology, which is dominated by ring-shaped depressions attributed to the dewatering of glacial-lacustrine clays. Ten multi-cores were recovered from the survey area. The cores were scanned for magnetic susceptibility (MS), dated by 210 Pb and analyzed for water content, total organic carbon (TOC) and nitrogen (TON), biogenic silica (BSi), and total (THg) and methyl (MeHg) mercury. MS profiles varied considerably, inferring substantial centennial-scale differences in sedimentation history among the core sites. Concentration profiles of the analyzed constituents displayed differences of about ± 15% TOC, ± 40% BSi, ± 50% THg and ± 50% MeHg. Total mercury and methylmercury concentrations were typical of past measurements, and the mean THg accumulation rate (12 μg/m 2 year) was similar in magnitude to that of atmospheric Hg deposition. Sediment mass accumulation rates (MAR) ranged among the cores between average values of about 50 g/m 2 year in the ring centers to as high as 180 g/m 2 year between rings. Temporal variation in MAR within cores varied considerably on a decadal scale as well. Sediment redistribution by bottom currents over the complex morphology of the Lake Superior basin is not uniform in space and time, and indicates that a single core from any given area in the lake may not reflect the true history of environmental conditions that extend even a few hundred meters beyond the core site.

The advent and proliferation of digital terrain technologies have spawned concomitant advances in coastal geomorphology. Airborne topographic Light Detection and Ranging (LiDAR) has stimulated a renaissance in coastal mapping, and field-based mapping techniques have benefitted from improvements in real-time kinematic (RTK) Global Positioning System (GPS). Varied methodologies for mapping suggest a need to match geospatial products to geomorphic forms and processes, a task that should consider product and process ontologies from each perspective. Towards such synthesis, coastal morphodynamics on a cuspate foreland are reconstructed using spatial analysis. Sequential beach ridge and swale topography are mapped using photogrammetric spot heights and airborne LiDAR data and integrated with digital bathymetry and large-scale vector shoreline data. Isobaths from bathymetric charts were digitized to determine slope and toe depth of the modern shoreface and a reconstructed three-dimensional antecedent shoreface. Triangulated irregular networks were created for the subaerial cape and subaqueous shoreface models of the cape beach ridges and sets for volumetric analyses. Results provide estimates of relative age and progradation rate and corroborate other paleogeologic sea-level rise data from the region. Swale height elevations and other measurements quantifiable in these data provide several parameters suitable for studying coastal geomorphic evolution. Mapped paleoshorelines and volumes suggest the Virginia Beach coastal compartment is related to embryonic spit development from a late Holocene shoreline located some 5 km east of the current beach.

This paper proposes a cheap and fast method for est imating the bathymetry of hydroelectric reservoirs. Brazil has more than 30 l arge hydroelectric reservoirs with volume exceeding one billion cubic meters. The hydroelectric sector is responsible for 97% of energy generation being the largest hydroele ctric park in the world. These dams, however, cause a series of environmental, social an d economic impacts, which need to be monitored. Among the variables affecting the env ironmental impact posed by reservoirs, depth has a key role because it acts on the aquatic system hydrodynamics. Reservoir depth distribution, the bathymetry, is al so a fundamental factor controlling physical-chemical and biological properties of the system. In Brazil, the acquisition of bathymetric information for the large reservoirs, h owever, is not a simple task, because: 1) most of the topographic maps available in the ar ea covered by the lake have very small scale (1:100 000 and smaller); 2) larger char ts are property of the hydropower companies and are classified; 3) the size of the re servoirs prevent the use of bathymetric surveys due. The challenge therefore is how to comb ine the use of low precision topographic charts from the period previous to rese rvoir filling, SRTM data to obtain a bathymetric map which could be used for planning echo-bathymetric missions so as reducing both cost and time of data acquisition and processing.

The selection procedure of a potential site for an offshore wind farm around Jeju Island is presented using the optimization technique. The statistical model was developed by analyzing the sea wind data from RDAPS/KMA for year 2006, and the meso-scale digital wind map was prepared. To develop the high resolution spatial calibration model, artificial neural network (ANN) models were used to construct the wind and bathymetric maps. Accuracy and consistency of wind/bathymetric spatial calibration models were obtained using analysis of variance. The optimization problem was defined to maximize the energy density satisfying the criteria of maximum water depth and maximum distance from the coastline. The candidate site was selected through genetic algorithm (GA). From the results, it is possible to predict roughly a candidate site location for the installation of the offshore wind farm, and to evaluate the wind resources of the proposed site.

A detailed comparison was made of two bathymetric charts of the Lagoon of Venice (LV) from 1970 and 2000, in tandem with a comparison of sediment grain size data. Analysis of the data revealed marked changes in both morphology and sedimentation, with more than 50% of the 400 km2 assessed in this study 15–20 cm shallower in 1970 than in 2000. The four sub-basins into which the LV is subdivided saw different patterns of change. The Northern basin A was identified as “pristine”, i.e. still in quasi-natural condition, with slight clay enrichment and a small degree of deepening (4–5 cm), essentially due to sea level rise (SLR). The bathymetry and sedimentology of the northern-central sub-basin B (identified as “urban”) and the southern-central basin C (identified as “open”) were affected by infill activities and excavation of industrial navigation channels in the 1970s, causing the loss of ~ 60 km2 of mudflats, and creating an “open” lagoon. The southernmost basin D (identified as “exploited-subsiding”) of the LV was found to be relatively unchanged and still in semi-natural condition. Comparison of sediment types showed depletion of fine-grained fractions (< 22 ¼m) in all sub-basins except the northernmost one. Consequent enrichment in sand (> 63 ¼m) was recorded, except in the southern-central sub-basin C where medium and coarse sand fractions declined. The results suggest that climate-related SLR accounts for a small fraction of bathymetric change, whilst variations in hydrodynamics (currents and wind patterns) and sediment supply are likely causal factors for the different evolution of the four sub-basins. Definition of the attributes of each sub-basin provided data that was essential not only for the LV but also for predicting the fate of transitional environments facing both anthropic (fishing, navigation, land use changes) as well as natural (SLR, eustatism) forcing factors.

We report new geophysical and petrological data collected at the southern tip of the Parece Vela Basin in the Philippine Sea. The Parece Vela Basin, which was formed as a backarc basin behind proto Mariana arc-trench system from late Oligocene to middle Miocene, provides us a good opportunity to study the nature of successive backarc basin formations in the Philippine Sea and the relationship between are and backarc magmatisms. Regional bathymetric map derived from satellite altimetry shows that the southern tip of the basin, now located just west of the Yap arc-trench system, has unique morphological and tectonic features which include: 1) the absence of spreading center or its trace, 2) shallow average depth, and 3) enigmatic curved structures. Our newly collected high-resolution bathymetric data reveal that the spreading fabric similar to the central Parece Vela Basin exists to the north of 9 degrees 20'N. Thus it appears that the present-day Yap arc and backarc region represent the western half of the seafloor that was produced by the early E-W and the following NE-SW spreading in the northern and central Parece Vela Basin, and that the eastern counterpart now lies west of the West Mariana Ridge. Unlike the northern Parece Vela Basin, there appears to be no evidence for a systematic propagation of spreading center in the southern part. Instead two rift segments, one which extends from the central Parece Vela Basin and the other which lies within the western remnant arc (Kyushu-Palau Ridge), overlap at the southern tip of the basin, producing a complex seafloor that includes curvilinear deeps and deformed topographic highs. (c) 2007 Elsevier B.V. All rights reserved.

A seven-year long data set from 1998 to 2005 of sand waves in the Marsdiep tidal inlet in the Netherlands is presented. The sand waves are visible on digital terrain models (DTMs) that were compiled from water depths obtained with a ferry-mounted acoustic Doppler current profiler. This multi-year data set allows to study the spatial and temporal evolution of sand-wave migration, height, length, asymmetry, and orientation. Horizontal migration rates were successfully obtained with a simple cross-correlation technique similar to techniques used in particle tracking. The study area can be divided in roughly two halves. In the southern half of the inlet, the sand waves are of the progressive type with area-mean heights of about 3 m and lengths of about 190 m. In the northern half, the sand waves are asymmetrical-trochoidal with area-mean heights of about 2 m and lengths of about 165 m. Across the inlet, the sand waves migrate in the flood direction with rates between 0 and 90 m y - 1 . Only the progressive waves in the southern half migrate in directions perpendicular to their crests. A striking observation is the seasonal variability in height and migration of the sand waves in the northern half of the inlet. The sand-wave heights are about 0.5 m higher in fall than in spring and the migration rates are about 30 m y - 1 higher in winter than in summer. This paper only presents observations and analysis techniques. In a subsequent paper, the ADCP-current data will be applied to explain the spatial and seasonal variability of the sand waves.

Multibeam data collected during the United States Southern Ocean Global Ocean Ecosystems Dynamics cruises in 2001 and 2002 aboard the R/VIB Nathaniel B. Palmer were augmented with available multibeam and centerline bathymetry data from a variety of sources to compile a bathymetric data set for the continental shelf west of the Antarctic Peninsula. This new bathymetry data set provides an improvement in the resolution of the bathymetry of the region. The improved data set was used to construct a high-resolution bathymetric map of the continental margin west of the Antarctic Peninsula from 65° to 71°S and from 65° to 78°W.

Surficial and subsurficial sediment samples derived from gravity cores, selected from the harbour of Patras, Greece, were analyzed for grain size, water content, bulk density, specific gravity, organic carbon content and specific activities of natural radionuclides and 137 Cs. The specific activities of 232 Th, 226 Ra, 40 K and 137 Cs were measured radiometrically. The radionuclides 238 U and 232 Th were also analyzed using the INAA. The differences found between the specific activities of the natural radionuclides measured by the two methods are of no statistical significance. The sediment cores selection was based on a detailed bathymetric and marine seismic survey. Through the study of the detailed bathymetric map and the seismic profiles it was shown that ship traffic is highly influential to the harbour bathymetry. The granulometric and geotechnical properties of the sediments and therefore the specific activities of the natural radionuclides and 137 Cs seem to be controlled by the ship traffic. Relationship between radionuclide activity concentrations and granulometric/geotechnical parameters was defined after the treatment of all the analyses using R-mode factor analysis. The natural radionuclide activities are related to the fine fraction and bulk density of the sediments, while 137 Cs is mainly influenced by the organic carbon content. In addition, 238 U and 226 Ra seem to be in close relation with the heavy minerals fraction in coarse-grained sediments with high specific gravity.

Changes in the morphology of the Mersey Estuary, and their possible causes, have been investigated using Historical Trend Analysis and Expert Geomorphological Assessment. Historical bathymetric charts were digitised and analysed within a GIS to provide quantitative estimates of changes in areas and sediment volumes above and below selected elevation planes. The results show that the estuary experienced major changes over the last 150 years, notably between the late 19th century and ca. 1950. An analysis of data relating to possible natural and human factors which could have influenced these changes suggests that training wall construction and dredging in the Outer Estuary and Liverpool Bay was the most significant factor contributing to change during this period. These activities modified the hydrodynamic and sediment transport regime in a way which enhanced an existing natural tendency for movement of sediment from Liverpool Bay and the Outer Estuary into the Inner Estuary. Changes in other factors, including sea level, tidal range, wind/wave climate, freshwater flow and embanking/land reclamation, were of relatively minor importance. Between 1950 and 1977 the rate of sediment accumulation in the Inner Estuary declined as the estuary approached a new condition of dynamic equilibrium, and since 1977 there has been a slight net loss of sediment. Under these conditions the changes in natural forcing factors, such as sea level and storminess, are likely to have a relatively greater effect on the estuary than in the past. [KEYWORDS: Estuaries; Morphology ; Bathymetry ; Sedimentation ; Historical Trend Analysis ; Expert Geomorphological Assessment; Mersey]

Recent studies regarding the climate variability in South America during the 20th century, revealed the existence of climate cycles that influenced the hydrologic conditions in the Parana River basin, one of the largest in the continent. How that variability affected the channel morphology of this river in its middle reach is quantitatively analyzed in this paper. The link between climate, hydrology and channel morphology is obtained through the computation of effective discharge. This discharge implicitly synthesizes the point hydrologic and bed sediment transport changes in an alluvial stream during a relatively long period. The results were obtained studying, with increasing detail, two channel reaches 373 km and 25 km long, respectively. The analysis involved the processing of more than 180 bathymetric charts, satellite images and hydraulic and sedimentologic data recorded in the Parana River since the very beginning of the 20th century. A rather detailed description of the treatment made with this information is given in the paper. It is shown that three periods of different effective discharges fairly well correlated with reported climatic fluctuations occurred during the last 100 years, i.e. two periods of high discharges (at the century beginning and from 1970 till present) and another of relatively low discharges between 1930 and 1970. Morphologic parameters of the main channel, such as mean width, thalweg sinuosity, braided index and aspect ratio, increased or decreased in correspondence with those variations. In transitional channels (between meandering and braided) like the Parana River, careful study of the thalweg behavior is a key issue, if a proper approach to the dynamic of morphologic processes operating on the whole channel is intended. Finally, on the basis of theoretical (extreme hypotheses approach) and empirical results, it is suggested that the Parana River main channel would not be adjusted to the present high values of effective discharge. Thus, larger erosion of banks (channel widening) and increases in the other cited morphologic characteristics will occur if those values persist.

The 1960 bathymetric map of Pfannenstiel showed a submarine volcano west of the Peloponnesus which could not be confirmed by modern bathymetric surveys. Pfannenstiel's interpretation was supported by a report of flames on the sea in 1886. It is most likely that the strong earthquake on August 27, 1886, triggered a submarine mud volcano eruption and gas escapes on the Mediterranean Ridge (MR), and burning gas was observed from several places on land and on sea.

Between 1938 and 1945, the Sinu River changed its course and started a new delta at a site known as Tinajones. The change took place after the infilling of Cispata Bay, the site of the previous delta. The infilling is studied with two isopach maps made from bathymetric charts from 1762, 1849, and 1938. The isopachs help show the distribution of the sediments inside the bay and provide estimations of sedimentation rates. The results are compared with the sediment distribution and estimated sedimentation rate found for the delta at Tinajones. The results suggest that the infilling of the Cispata Bay produced the river avulsion and the change to Tinajones and probably was accelerated by sediments that came from outside the bay.

The morphotectonic structure of the North Aegean Basin is studied on the basis of a new detailed swath bathymetric survey. The resulting bathymetric map is presented in reduction with 20-m isobaths. The slope analysis gives an accurate scheme of the geometry of the basin and distinction of several sub-basins (approximately 20). The overall basin geometry is a rectangular tetrahedron shaped by the major slope discontinuity separating the continental platform from the continental slope. The area distribution with depth shows a maximum at depths between 300 and 450 m along the sub-horizontal edge of the continental platform and at depths between 1000 and 1200 m at the basinal areas of the sub-basins. The separation of the western part of the North Aegean Basin from the eastern part (Saros Bay) is very clear in the area between Limnos and Thasos, with a maximum depth of 490 m. The 3.2% of the basin area is characterized by slope values >20%, which correspond to active fault zones. Their trend is NE–SW (N46°) and NW–SE (N136°). Some secondary E–W faults are also present within the basin with morphological expression only on the orientation of slopes

The 130-km-long Tenryu Canyon is an active deep water meandering canyon transversely developed on the tectonically active Tokai (Eastern Nankai) accretionary prism, where the multiple intraplate deformation caused by the arc–arc Izu collision. Over 2000 km of EM 12 data, 3.5-kHz profiles and PASISAR profiles obtained during the KAIKO-TOKAI Project, 1996, IZANAGI data, the bathymetric chart, and the preexisting seismic profile data, enable us to better understand the geomorphology and development of the Tenryu Canyon. The Tenryu Canyon is a very steep entrenched channel with its lower stream steeper in both canyon slope and channel slope. Similarly, the relative height between the channel bottom and the levee surface tends to increase unusually toward the lower reach. A likely interpretation of such geomorphological features is that the Nankai Trough floor, as the termination of the Tenryu Canyon, has subsided, associated with subduction of the Paleo Zenisu ridge. Based on the result of a quantitative analysis, the total amount of relative subsidence of >800 m was estimated in the Nankai Trough floor. As a result, the Tenryu Canyon has rejuvenated, catching up the topographic gap between the subsided Nankai Trough floor and the continental slope.

The determination of shallow water depth in high-energy tidal inlets is essential to model and to forecast the navigation channel position or the short-term topographic evolution of beaches. Colour satellite imagery provides, at low cost, complete maps of areas that are difficult to map by traditional hydrographic means due to their size and their rough underwater morphology. In order to calibrate SPOT images to derive bathymetric maps, a simple method applied to shallow waters of a moderately turbid tidal inlet has been carried out. Its development is based on a set of field measurements, including the reflectance of the water and of the bottom sediment, the vertically averaged diffuse attenuation coefficient, and the concentrations of inorganic particles in suspension, of chlorophyll a and pheopigments and of dissolved organic carbon (DOC). From these data, it appears, first, that the water reflectance is directly linked to the depth, and second, that the water reflectance varies slowly with the turbidity in this area for total suspended matter (SM) concentrations lower than 9 mg l−1. The extinction of light with depth has been characterized in the inlet. The relationship obtained is slightly different from that observed in clear waters. The bathymetric models established for the clearest waters do not calculate the depth accurately. In the contrary, reflectance code adapted to Case II water type, calibrated with in situ measurements, allows us to retrieve depth down to 6 m and for total SM concentrations ranging from 0.2 to 9 mg l−1. This relationship has been applied to five SPOT images of the mouth of Arcachon lagoon. The accuracy of the derived map has been assessed by in situ depth measurements. The mean difference between measured depths and computed depths is about 20%. This accuracy is adequate to assess the inlet morphodynamics quantitatively, which is necessary for middle-term to short-term mathematical modeling of the 3D inlet evolution.

This paper presents selections from and a synthesis of a high resolution bathymetric, sparker and deep-towed seismic reflection data set recently acquired by the French Ifremer R.V. Le Suroit in an E–W deep trough that forms the northern half of the Sea of Marmara in NW Turkey. It includes the first high resolution complete bathymetric map of this area. A single, throughgoing dextral strike–slip fault system, which is the western continuation of the northern branch of the North Anatolian Fault, cuts this trough lengthwise and joins the 1999.8.17 Kocaeli earthquake fault with the 1912.8.09 Sarkoy–Murefte earthquake fault, both of which display strike–slip offset. In its eastern one fourth, the structure follows closely the northern margin of the deep trough, whereas in the west it hugs its southern margin. The eastern one fourth of the structure has a minor component of its displacement distributed across the deep trough owing to a possible original bend in the course of the dextral structure. The present course of the North Anatolian Fault in the Sea of Marmara originated some 2×105 a ago, by cutting across the older basin fabric generated by a dominant NNE–SSW extension before it began taking up major motion in the Pliocene.

A recent cruise of the Suroit using new technologies for acquisition and processing of acoustic data (very high-resolution seismic and swath mapping) associated to an accurate satellite positioning, allowed producing a new bathymetric map of the upper part of the canyon. It shows the meandering shape of the canyon and superposed polyphase terrace. Such a morphology is due to activity of gravity flows that occurred as soon as the Upper Eocene. Very high-resolution seismic data allowed to confirm the influence of old tectonic structures on the location and the general shape of the canyon and to show that neotectonics that affects Plio-Quaternary deposits corresponds to recurrent activity of old tectonic structures.

An illustration of how sediment transport may be measured over a large dynamic intertidal area at reasonable cost and spatiotemporal resolution using the waterline method employing remote sensing and hydrodynamic modelling is presented. Areas and volumes of accretion and erosion were measured in the study area of Morecambe Bay in north-west England over the period 1992–97. Tidal asymmetry is considered to be the dominant agent of sediment movement in the bay, with waves being of secondary importance. Waterlines (i.e. land-sea boundaries) were extracted from 31 synthetic aperture radar images of the bay covering a substantial fraction of the tidal range. Heights were attached to the waterlines using water elevations from nested hydrodynamic tide-surge models. Interpolation in space and time was carried out to produce a continuous spatiotemporal height map of the intertidal zone. Height maps with a spatial resolution of about 50 m and height accuracy of about 40 cm were constructed over an area of about 350 km 2 . Strong temporal decorrelation in the bay limited the height accuracy achievable. Differences between height maps for 1992–94 and 1995–97 allowed sediment volume changes to be extracted. The intertidal region showed a loss of 16·1±4·5×10 6 m 3 over the period, almost all the change being due to a significant decrease between mean sea level and the low water mark. Changes were also measured in three of the main river estuaries within the bay, the Leven, Kent and Lune. These included movement of the Leven north-east by about 2 km cutting into Cartmel Wharf, accretion seaward of Grange-over-Sands and changes in the low water channels at the mouth of the Lune. These changes could be used to validate sediment transport models of the bay.

The bathymetric map (scale 1/25 000) of the outer shelf near Marseilles (Collina-Girard, 1992) shows a karstified area (dolins and polje). Statistical anomalies in the distribution of thalweg lengths are correlated with NE-SW anticline axes revealed by sismic survey (Leenhardt et al., 1969). Therefore the validity of this geomorphological method (Gvin, 1965) is once more proven and its application completes geophysical data in this submarine area.

The Swedish ‘Arctic Ocean-96’ expedition to the central Arctic Ocean with the icebreaker Oden carried out a geological=geophysical program focused mainly on Lomonosov Ridge sediments. Approximately 195 km of high-resolution seismic data from the ridge crest and slope were collected with a chirp sonar system providing new insights into the sediment stratigraphy and the accompanying depositional history. These data reveal evidence of substantial erosion that acted in laterally limited areas on shallow parts of the investigated ridge segment. More than 50 m of sediment stratigraphy is missing in the most eroded parts. Moreover, the chirp sonar records indicate that, below the erosional surface, the ridge crest and slope is characterized by a low-energy sedimentary environment. The termination of the erosional phase is indicated by a prominent reflector. The subsequent depositional phase resulted in an approximately 3 m thick stratigraphic unit. The cause of the erosion is attributed to either ice grounding or current erosion. Furthermore, Oden echo sounding data has been used together with data from the US Navy SCICEX program in order to update existing bathymetric charts in the ‘Arctic Ocean-96’ working area. The update shows a narrower ridge crest with a different outline than in previously published charts with a minimum depth of 607 m which is the shallowest depth of the Lomonosov Ridge recorded (in the public domain) in the central Arctic Ocean. © 1999 Elsevier Science B.V. All rights reserved.

A detailed regional bathymetric map has been analysed and correlated with seismic and sedimentological data. The morphostructural features identified between 90 and 120 m are considered as well preserved coastal enviromnent deposits accumulated during the last glacial maximum and the eustatic sea level rise of the Holocene. They are analogues of Pleistocene seismic units and reservoirs previously described in the area.

A Uniboom survey was carried out in Bracciano Lake (Northern Latium) in order to obtain further information about its structural and morphological features. The authors give an updated geophysical interpretation of the lake by combining the findings of the seismic survey with those from gravity and magnetometric prospecting. Through seismic sections, obtained by developing a new bathymetric map, some sedimentary and volcanic structures were identified.

Summarization: A 2-D hydrodynamic finite element model (RMA-2V) with mesh generation tools (Fast-TABS) is used to simulate the current velocities in the St. Clair and Detroit rivers. The required shorelines and spot depths were digitized from the bathymetric charts and the NOS (National Ocean Service) hydrographic database using Geographic Information Systems technology. The field data obtained from the tracking of drogues via aerial time-lapse photography were used to calibrate the model. A statistical comparison between field and simulated data revealed a very good agreement between the simulated and observed currents. Presented on: Journal of Great Lakes Research

Recently, there have been increasing doubts of the existence of a seamount “Novara Knoll”, between Kerguelen and Amsterdam Islands, because any hydrodynamical signature in favor of such a topographic releif has never been revealed from our previous analysis of satellite-tracking buoy data as well as historical hydrographic data. Checking of satellite-driven geopotential anomaly and historical bathymetric charts for the area did not show anything more. A precise bathymetric survey over the feature made in April 1991 on board the Marion Dufresne confirmed definitively the non-existence of “Novara Knoll”.

The North Banda Sea (Eastern Indonesia) is an oceanic domain whose origin is controversial. New bathymetric and seismic reflection profiles, in addition to those published previously, allow presentation of a new bathymetric map and structural sketch of this basin. A general NW-SE structural pattern appears to be the result of: first, the orientation of very large NW-SE strike-slip faults. Among them the West Baru fracture zone is described for the first time and can be traced for about 300 km; second, the present direction of convergence seems to be oriented NE-SW. This has resulted in the faulting and underthrusting of the Banda Sea crust beneath the East Sulawesi margin, particularly well expressed in the north. As a consequence of the convergence along the Tolo Thrust an active accretionary prism is developed and a peripheral bulge arches the central domain of the North Banda Sea. The nature of the North Banda Sea floor is still unknown but several good dredging sites are identified to solve this major problem in the region.

A compilation of Sea Beam data on the right-stepping overlapping spreading center (OSC) at 16°20′N on the East Pacific Rise (EPR) and in the surrounding region is presented. Sea Beam data from the rise flanks at 16°20′N reveal three deep basins, at least one of which is flanked by a curved ridge whose morphology is similar to that at the offset. The widths of these offaxis basins range from 8 to 13 km and allow an estimate to be made of the sizes of the offsets at which they were formed. It is proposed that they represent traces on the rise flank which provide a record of the development of the offset and a basis for prediction of its future evolution. The repeated pattern of abandoned overlap basins and cuspate ridges supports the notion that OSCs are episodic on a time scale of approximately 200,000 years and are cyclic in nature. It also reveals an alternation of dominance between the southern and northern segments, which have shifted the location of the discontinuity along the axis so as to create zig-zag traces of basins on the ridge flanks.

Statistical analysis of underway bathymetric profiles of the Philippine Sea back-arc basins; the Mariana Trough, the Shikoku Basin, the Parece Vela Basin and the West Philippine Basin reveals an age-depth correlation in the basins. The basement depths of the Philippine Sea range from 3200 to 6000 m with their ages from 0 to 60 Ma. The age-depth curve of the whole Philippine Sea can be represented by the following equation: Depth (m) = 3222 + 366√Age (Ma) The equation shows that the basement depth of the Philippine Sea is about 800 m deeper than that of the major ocean floors of the same age. The coefficient of 366 in this equation is close to that for major oceans, 350. This suggests that the cooling processes of the lithospheres in the Philippine Sea and major oceans are similar to each other, whereas the structure and composition of the deeper layers of the Philippine Sea seem to be different from those of major oceans. Our analysis of ETOP digital bathymetric data, however, indicates that this relationship does not hold for some other marginal basins. Marginal basins other than back-arc basins generally follow the age-depth curve of major oceans. Young back-arc basins (

A new map showing the major features of the Dead Sea transform fault system based on seismicity, satellite imagery, geological maps and bathymetric charts is presented. Special attention is given to the possible northward continuation of the transform system beneath the Mediterranean Sea near Ed Damur, south of Beirut. The map shows the Dead Sea transform system to be a series of offset, overlapping, left-lateral transform faults with a rhombochasm between each pair. The system has similarities with the equatorial fracture zones in the Atlantic Ocean. Throughout, the Dead Sea transform system is considered in its regional setting, i.e. as extending from the Red Sea spreading centre in the south to the Eurasian collision zone in the north. It is suggested that it may intersect the latter somewhere east of Cyprus making that area the northernmost termination of the Dead Sea transform system.

Phipps' expedition into the fringe of the Eurasia Basin in 1773 marked the beginning of Arctic Ocean research in the modern sense, while a century later Nansen's Fram drifted across the Eurasia Basin. The early period of sailing ships and dog-sledding ended with Stefansson's Canadian Arctic Expedition during World War I. Papanin's ice drift from the North Pole into the Greenland Sea, in 1937, marked the beginning of modern exploration in which aircraft, icebreakers and submarines became the standard means of transportation. After World War II the Soviets introduced their North and North Pole Series operations of drifting ice stations which are still ongoing today. During the fifties, sixties and early seventies the U.S. carried out a program of airborne surveys into the Canada Basin, manned a number of drifting ice stations, and released bathymetric data from their early nuclear submarine expeditions. The Canadian Polar Continental Shelf Project, created in 1958, has supported 3000 research projects over a period of 30 years and thereby placed Canada among the leaders in Arctic Ocean research. The LOREX and Fram expeditions in 1979, followed by the CESAR expedition, the establishment of an ice island research station, and the cruises of the scientific research ships Ymer and Polarstern marked the beginning of a new era — one of unprecedented cooperation between institutions and nations, and between scientific disciplines. It reflects an advance in understanding: the Arctic Ocean is being viewed in a global setting in which the interaction of physical, chemical and biological processes regulates the total earth system.

The Manihiki Plateau is a large, shallow area of old oceanic crust near the southwest margin of the Pacific Plate. Recent geophysical surveys and traverses have allowed the preparation of a new bathymetric chart showing three distinct provinces, the High, the North, and the Western plateaus, and systems of deep internal troughs. Up to 1 km of sediment occurs both in the troughs and on the shallow plateaus. From seismic reflection profiles we infer that there is a major, sometimes angular, early Tertiary unconformity, that the plateau has always been relatively shallow, and that the High Plateau may originally have been close to sea level. The unusual character of this area of crust is probably inherited from a period of unusually voluminous volcanic eruptions at the time of lithospheric generation when the plateau was at or near the middle Cretaceous triple junction between the Pacific, Antarctic, and Farallon plates.