Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>shelf valley </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>shelf valley</SPAN><SPAN>s of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>Valleys incised more than 10 m into the continental shelf were digitised by hand. To qualify for inclusion in this study, shelf valleys had to be greater than 10 km in length and >10 m in depth overall. Only features that had a definite elongate shape were included as valleys, nominally more than 4 times greater in length than width. Features that intersected the shelf break and extended both onto the shelf and down-slope (where they become submarine canyons) were also included.</SPAN></SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>basin </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>basin</SPAN><SPAN>s of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>Basins are “a depression, in the sea floor, more or less equidimensional in plan and of variable extent”</SPAN></SPAN><SPAN><SPAN>(IHO, 2008). In this study basins are restricted to seafloor depressions that are defined by closed bathymetric contours. Basins were mapped based on the identification of the most shoal, closed, bathymetric contours, examined regionally for the major ocean basins and shelf seas.</SPAN></SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The abyss</SPAN><SPAN>al classification</SPAN><SPAN>geomorphic feature layer represents the spatial extent of the abyssal areas of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). The abyss is the area of seafloor located at depths below the foot of the continental slope and above the depth of the hadal zone (defined as deeper than 6,000 m). The abyss</SPAN><SPAN>al classification</SPAN><SPAN>feature layer was created by clipping a layer representing the ocean with the shelf, slope and hadal layers. </SPAN><SPAN>The resulting layer was then classification into areas of plains, hills and mountains based on variation in topography.</SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>trough </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>troughs</SPAN><SPAN> of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>The IHO (IHO, 2008)</SPAN></SPAN><SPAN><SPAN> definition of a trough is “a long depression of the sea floor characteristically flat bottomed and steep sided and normally shallower than a trench”</SPAN></SPAN><SPAN><SPAN>. In this study we found that troughs are also commonly open at one end (i.e. not defined by closed bathymetric contours) and their broad, flat floors may exhibit a continuous gradient along a thalweg. Troughs may originate from glacial erosion processes or have formed through tectonic processes. In this study, glacial troughs incised into the shelf are a separate category; here we include all troughs not of a glacial origin, typically superimposed on the slope and/or abyssal base layers. Trenches that have been infilled with sediment may evolve into troughs, as appears to have occurred in troughs adjacent to</SPAN></SPAN><SPAN><SPAN> North and South America, for example. Slumping on the sides of some troughs has formed a bridge across the trough, thereby dividing it into two separate sections (see “bridges”</SPAN></SPAN><SPAN> below). In this study all troughs were digitised by hand based on the interpretation of 100 m bathymetric contours.</SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>terrace </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>terraces</SPAN><SPAN> of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>Terraces are “An isolated (or group of) relatively flat horizontal or gently inclined surface(s), sometimes long and narrow, which is (are) bounded by a steeper ascending slope on one side and by a steeper descending slope on the opposite side”</SPAN></SPAN><SPAN><SPAN> (IHO, 2008). In this study terraces (broad steps) were calculated based on the gradient of the SRTM30_PLUS model. The SRTM30_PLUS model was masked using the slope feature layer (i.e. terraces we only mapped on the continental slope). </SPAN></SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>sill </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>sills</SPAN><SPAN> of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>Sills are “</SPAN></SPAN><SPAN><SPAN>a sea floor barrier of relatively shallow depth re</SPAN></SPAN><SPAN><SPAN>stricting water movement between basins”</SPAN></SPAN><SPAN><SPAN> (IHO, 2008). Thus every basin has a sill, over which fluid would escape if the basin were filled to overflowing. The identification of sills in this study is based on selecting contours at a specified interval of 10 m (shelf except for Antarctica), 50 m (Antarctic shelf) or 100 m (all other areas) depending upon the location. Selecting the most shoal, closed contour defines the basin; one contour interval above this typically identifies a discrete location where c</SPAN></SPAN><SPAN><SPAN>ontours “escape”</SPAN></SPAN><SPAN> from the basin and join into the regional bathymetry. This location is mapped as the sill. Sills were mapped for all of the major ocean basins and seas and for the larger basins perched on the continental shelf; sills were not mapped for the smaller basins perched on the slope or shelf or for the smaller abyssal basins.</SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>seamount </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>seamounts</SPAN><SPAN> of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>Seamounts are “</SPAN></SPAN><SPAN><SPAN>a discrete (or group of) large isolated e</SPAN></SPAN><SPAN><SPAN>levation(s), greater than 1,000 m in relief above the sea floor, characteristically of conical form”</SPAN></SPAN><SPAN><SPAN> (IHO, 2008). Seamounts are thus defined as peaks that rise over 1,000 m above the seafloor, calculated based on the SRTM30_PLUS model. We adhered str</SPAN></SPAN><SPAN><SPAN>ictly to the requirement that seamounts are “of conical form”, thus distinguishing “seamounts”</SPAN></SPAN><SPAN><SPAN> (having a length/with ratio <2) from ridges (having a length/wid</SPAN></SPAN><SPAN><SPAN>th ratio ≥</SPAN></SPAN><SPAN>2). The criterion of a length/with ratio <2 for seamounts is consistent with the geomorphic analysis of Mitchell (2001). Seamounts are, furthermore, distinguished from flat-topped guyots</SPAN><SPAN>.</SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>guyot </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>guyots</SPAN><SPAN> of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>Guyots are “</SPAN></SPAN><SPAN><SPAN>an isolated (or group of) seamount (s) having a comparatively smooth flat top. Also called tablemount</SPAN></SPAN><SPAN><SPAN>(s)”</SPAN></SPAN><SPAN><SPAN> (IHO, 2008). In this study the seamount base layer was used to mask the SRTM30_PLUS model. The gradient of the resulting grid was calculated (ArcGIS 10->DEM Surface Tools (Jenness 2012)->Slope, Slope computation method = 4-cell method). The gradient was classified into areas >2 degrees and areas <2 degrees. The areas less than two degrees were converted into vector layers. Where these occurred at the top of seamounts and were greater than a minimum size threshold (10 km</SPAN></SPAN><SPAN><SPAN>2</SPAN></SPAN><SPAN><SPAN>) they were flagged as possible guyots. These possible guyots were then visually checked and either classified as a guyot or a seamount. Additionally the remaining seamounts were visually checked to see whether any with flat tops had been missed in the classification process. The geomorphic features map of Agapova et al (1979) was used in addition to the GEBCO Gazetteer of geographic names of undersea features (IHO-IOC, 2012), to ensure all previously mapped features were assessed for inclusion in our map.</SPAN></SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>shelf </SPAN><SPAN>classification </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>low, medium and high profile shelf </SPAN><SPAN>areas of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>The continental shelf is defined by IHO (2008)</SPAN></SPAN><SPAN><SPAN>as “</SPAN></SPAN><SPAN><SPAN>a zone adjacent to a continent (or around an island) and extending from the low water line to a depth at which there is usually a mark</SPAN></SPAN><SPAN><SPAN>ed increase of slope towards oceanic depths”</SPAN></SPAN><SPAN>. The low-water mark is taken in this study as the 0 m depth contour. The shelf break (i.e. the line along which there is marked increase of slope at the seaward margin of a shelf) was digitised manually at a nominal spatial scale of 1:500,000 in ArcGIS based on 10 m, 50 m and 100 m contours, depending on the slope and bathymetric profile of the region. In most cases 100 m contours were sufficient at the selected scale of 1:500,000 to identify the shelf break. However, where there was a gradual break in slope over a broad area, more closely spaced contours were used. Floating ice shelves cover large sections of the Antarctic continental shelf and these areas were simply left blank.</SPAN><SPAN> </SPAN><SPAN><SPAN>A classification of the continental shelf based on vertical relief yielded three classes: Low-relief shelf; Medium-relief shelf; and High-relief shelf. To generate these classes, the SRTM model was sub-classified based on the variation over a five-cell radius into areas of low (< 10m), medium (10-50 m) and high (>50 m) vertical relief.</SPAN></SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>rise </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>rises</SPAN><SPAN> of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN>The continental rise was digitised by hand at a nominal spatial scale of 1:3,000,000 in ArcGIS based on 100 m contours. A map of global ocean sediment thickness (Divins, 2003) was used to assist with identifying potential rise areas. In general the rise was confined to areas of sediment thickness >300 m.</SPAN><SPAN> </SPAN><SPAN>Criteria for identification of continental rises included the occurrence of a smooth sloping seabed as indicated by evenly-spaced, slope-parallel contours (Curray et al., 2002; Dowdeswell et al., 2008; Covault et al., 2011</SPAN><SPAN><SPAN>). In this study, the term “Rise” was restricted to features that abut continental margins and does not include the mid-ocean ridge (or “rise”</SPAN></SPAN><SPAN><SPAN>), which was mapped as a separate feature. The GEBCO Gazetteer of geographic names of undersea features (IHO-IOC, 2012) was used to ensure all named features were included.</SPAN></SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN><SPAN>The abyss geomorphic feature layer represents the spatial extent of the abyssal areas of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). The abyss is the area of seafloor located at depths below the foot of the continental slope and above the depth of the hadal zone (defined as deeper than 6,000 m). The abyss feature layer was created by clipping a layer representing the ocean with the shelf, slope and hadal layers. </SPAN></SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>canyon </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>canyon</SPAN><SPAN>s of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>Submarine canyons are defined as “</SPAN></SPAN><SPAN><SPAN>steep-walled, sinuous valleys with V-shaped cross sections, axes sloping outward as continuously as river-cut land canyons </SPAN></SPAN><SPAN><SPAN>and relief comparable to even the largest of land canyons”</SPAN></SPAN><SPAN><SPAN>(Shepard, 1963</SPAN></SPAN><SPAN><SPAN>). “Large”</SPAN></SPAN><SPAN>canyons were mapped in this study based on the definition of Harris and Whiteway (2011), which requires canyons to extend over a depth range of at least 1,000 m and to be incised at least 100 m into the slope at some point along their thalweg. Canyon mapping in this study was based on a combination of automated and expert interpretation of the SRTM30</SPAN><SPAN /><SPAN>PLUS model. </SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>bridge </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>bridge</SPAN><SPAN>s</SPAN><SPAN> of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>Bridge geomorphic features were first described by Gardner and Armstrong (2011</SPAN></SPAN><SPAN><SPAN>) as blocks of material that partially infill the Mariana Trench in four locations, forming a “bridge”</SPAN></SPAN><SPAN><SPAN>across the trench. In this study we have extended Gardner and Armstrong</SPAN></SPAN><SPAN><SPAN>’</SPAN></SPAN><SPAN><SPAN>s (2011) interpretation and applied it to all troughs and trenches and have identified a number of bridge features that appear to partially infill trenches and troughs in the global ocean. </SPAN></SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>shelf </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>shelf </SPAN><SPAN>areas of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>The continental shelf is defined by IHO (2008)</SPAN></SPAN><SPAN><SPAN>as “</SPAN></SPAN><SPAN><SPAN>a zone adjacent to a continent (or around an island) and extending from the low water line to a depth at which there is usually a mark</SPAN></SPAN><SPAN><SPAN>ed increase of slope towards oceanic depths”</SPAN></SPAN><SPAN><SPAN>. The low-water mark is taken in this study as the 0 m depth contour. The shelf break (i.e. the line along which there is marked increase of slope at the seaward margin of a shelf) was digitised manually at a nominal spatial scale of 1:500,000 in ArcGIS based on 10 m, 50 m and 100 m contours, depending on the slope and bathymetric profile of the region. In most cases 100 m contours were sufficient at the selected scale of 1:500,000 to identify the shelf break. However, where there was a gradual break in slope over a broad area, more closely spaced contours were used. Floating ice shelves cover large sections of the Antarctic continental shelf and these areas were simply left blank.</SPAN></SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>trench </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>trenches</SPAN><SPAN> of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>Trenches are “a long narrow, characteristically very deep and asymmetrical depression of the sea floor, with relatively steep sides”</SPAN></SPAN><SPAN><SPAN> (IHO, 2008)</SPAN></SPAN><SPAN><SPAN>. Trenches are generally distinguished from troughs by their “V”</SPAN></SPAN><SPAN><SPAN> shape in cross section (in contrast with flat-bottomed troughs). In this study trenches were mapped by selecting closed bathymetric contours that defined basins contained within the trench feature, and then joining the basin segments together by hand digitizing along more elevated sections. In this way, bridge features were also identified</SPAN></SPAN><SPAN><SPAN> (as coinciding with infilled sections of trenches; see section on “bridges”</SPAN></SPAN><SPAN><SPAN>). </SPAN></SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>glacial trough </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>glacial troughs</SPAN><SPAN> of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>Shelf valleys at high latitudes incised by glacial erosion during the Pleistocene ice ages form elongate troughs, typically trending across the continental shelf and extending inland as fjord complexes (Hambrey, 1994). The largest of these features are glacial troughs, characterised by depths of over 100 m (often exceeding 1,000 m depth) and are distinguished from shelf valleys by an over-deepened longitudinal profile that reaches a maximum depth inboard of the shelf break, thus creating a perched basin on the shelf with an associated sill (Hambrey, 1994). Glacial troughs were digitized by hand based on 50 m contoured data for the Antarctic and 10 m contoured data for other shelf areas. </SPAN></SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>escarpment </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>escarpment</SPAN><SPAN>s of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN>Escarpments are “an elongated, characteristically linear, steep slope separating horizontal or gently sloping sectors of the sea floor in non-shelf areas. Also abbreviated to scarp” (IHO, 2008). Escarpments, like basins, overlay other features (i.e. other individual features may be partly or wholly covered by escarpments). Thus features like the continental slope, seamounts, guyots, ridges and submarine canyons (for example) may be sub-classified in terms of their area of overlain escarpment.</SPAN><SPAN /><SPAN>Escarpments were calculated based on the gradient of the SRTM30_PLUS model.</SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>fan </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>fan</SPAN><SPAN>s of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>Fans are “a relatively smooth, fan-like, depositional feature normally sloping away from the outer termination of a canyon or canyon system”</SPAN></SPAN><SPAN><SPAN> (IHO, 2008). Since submarine fans are sediment deposits, the NGDC map of global ocean sediment thickness (Divins, 2003) was used to assist with identifying them. Fans overlay and comprise part of the continental rise and are located offshore from the base of the continental slope (Curray et al., 2002; Dowdeswell et al., 2008; Covault et al., 2011). Fans are inter-related with submarine canyons and sediment drift deposits; in cases where canyon axes extend across the rise, the canyon-channels may be flanked by sediment drift deposits, which have been grouped with fans in this study. Fans are defined in the present study by 100 m isobaths that form a concentric series exhibiting an expanding spacing in a seaward direction away from the base of the slope, sometimes clearly associated with a canyon mouth, but also comprising low-relief ridges between canyon-channels on the abyssal plain.</SPAN></SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>ridge </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>ridges </SPAN><SPAN>of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>Ridges in this study are confined to “an isolated (or group of) elongated narrow elevation(s) of varying complexity having steep sides, often separating basin features”</SPAN></SPAN><SPAN><SPAN> (IHO 2008)</SPAN></SPAN><SPAN><SPAN>. In this study “ridges”</SPAN></SPAN><SPAN><SPAN> were confined to features greater than 1,000 m in relief and do not include the mid-ocean ridges, which was mapped as a separate feature. </SPAN></SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>spreading ridge </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>spreading ridge</SPAN><SPAN>s of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>Mid-ocean spreading ridges are “the linked major mid-oceanic mountain systems of global extent”</SPAN></SPAN><SPAN><SPAN> (IHO, 2008)</SPAN></SPAN><SPAN><SPAN>.</SPAN></SPAN><SPAN><SPAN> Spreading ridges are distinguished from other ridges in this study (see definition of ridges below). They were mapped by hand based on their appearance as ridge-like features that coincide with the youngest ocean crust as mapped by </SPAN></SPAN><SPAN><SPAN>Mü</SPAN></SPAN><SPAN><SPAN>ller et al. (1997</SPAN></SPAN><SPAN><SPAN>) in their “</SPAN></SPAN><SPAN><SPAN>EarthByte</SPAN></SPAN><SPAN><SPAN>”</SPAN></SPAN><SPAN> digital age grid of the ocean floor. Spreading ridges that were not visible in the SRTM30_PLUS bathymetry (100 m contours) were not included in our interpretation, but there is otherwise no size limitation on spreading ridges.</SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>hadal </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>hadal </SPAN><SPAN>areas of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>The hadal zone is defined in this study as seafloor occurring at depths >6000m (based on the SRTM bathymetry grid). </SPAN></SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>rift valley </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>rift valley</SPAN><SPAN>s of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>Rift valleys were mapped as separate features in the present study where they are clearly evident in SRTM30_PLUS bathymetric data. Rift valleys are confined to the central axis of mid-ocean spreading ridges; they are elongate, local depressions flanked generally on both sides by ridges (Macdonald, 2001). They were mapped by hand based on 100 m contours. </SPAN></SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>plateau </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>plateau</SPAN><SPAN>s of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>Plateaus are “</SPAN></SPAN><SPAN><SPAN>flat or nearly flat elevations of considerable areal extent, d</SPAN></SPAN><SPAN><SPAN>ropping off abruptly on one or more sides”</SPAN></SPAN><SPAN><SPAN> (IHO, 2008). Plateaus were digitised by hand based on 100 m contours. In areas where plateaus abut the margin, the foot of slope was allowed to flow offshore to encompass the plateau feature, where a clear seaward dipping gradient was apparent. In other locations marginal plateaus are distinctly separate from the continental slope and form isolated, raised platforms. The geomorphic features map of Agapova et al (1979) and the GEBCO Gazetteer of geographic names of undersea features were used to ensure all named features were included.</SPAN></SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)
Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>The </SPAN><SPAN>slope </SPAN><SPAN>geomorphic feature layer represents the spatial extent of the </SPAN><SPAN>slope </SPAN><SPAN>areas of the worlds oceans based on interpretation of the SRTM30 plus v7 global bathymetry model. The layer is one of the 25 layers that make up the global seafloor geomorphic features map (Harris et.al. 2014). </SPAN><SPAN><SPAN>The slope is “the deepening sea floor out from the shelf edge to the upper limit of the continental rise, or the point where there is a general decrease in steepness”</SPAN></SPAN><SPAN><SPAN> (IHO, 2008). In this study, the foot of slope was digitised manually at a nominal spatial scale of 1:500,000 in ArcGIS based on 100 m contours and 3D viewing. ArcGIS was used to highlight zones of abrupt changes in seabed gradient (contour spacing) which suggests the foot of slope in many areas. In areas where marginal plateaus abut the margin, the foot of slope was allowed to extend offshore to encompass the plateau feature, where a clear seaward dipping gradient was apparent. Otherwise the first significant decrease in gradient encountered in a seaward direction from the shelf break was selected as the foot of slope. Note our foot of slope locations are based only on bathymetric data and our interpretation is not intended to define the foot of slope under Article 76 of the 1982 United Nations Convention on the Law of the Sea, particularly in areas of geomorphologically complex, continent-ocean transition.</SPAN></SPAN></P></DIV></DIV></DIV>
Service Item Id: ab9877e84b514604a5e20874622aa095
Copyright Text: The global seafloor geomorphic features map has been produced through a collaboration between Geoscience Australia, GRID-Arendal and Conservation International.
Reference: Harris et. al. (2014) Geomorphology of the oceans.Marine Geology (in Press)