Name: Guyots

Display Field: geomorphic

Type: Feature Layer

Geometry Type: esriGeometryPolygon

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-&gt;DEM Surface Tools (Jenness 2012)-&gt;Slope, Slope computation method = 4-cell method). The gradient was classified into areas &gt;2 degrees and areas &lt;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)

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YMin: -1.0755711905499998E7
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Spatial Reference: 102100  (3857)

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Type ID Field: N/A

Fields:

• objectid ( nullable: false, alias: objectid, type: esriFieldTypeOID )
• geomorphic ( nullable: true, length: 16, alias: Geomorphic, type: esriFieldTypeString )
• area_km2 ( nullable: true, alias: area_km2, type: esriFieldTypeDouble )
• height ( nullable: true, alias: Height, type: esriFieldTypeInteger )
• peak_depth ( nullable: true, alias: Peak_Depth, type: esriFieldTypeInteger )
• seamountid ( nullable: true, length: 10, alias: SeamountID, type: esriFieldTypeString )
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Supported Operations:   Query   Query Attachments   Query Analytic   Generate Renderer   Return Updates

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