Seamounts – Seamounts are “a discrete (or group of) large isolated elevation(s), greater than 1,000 m in relief above the sea floor, characteristically of conical form” (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 strictly to the requirement that seamounts are “of conical form”, thus distinguishing “seamounts” (having a length/with ratio <2) from ridges (having a length/width ratio ≥2). The criterion of a length/width ratio <2 for seamounts is consistent with the geomorphic analysis of Mitchell (2001). Seamounts are, furthermore, distinguished from flat-topped guyots
Estimates of the numbers of seamounts in the world ocean and their distribution have been published by Agapova et al., (1979), Craig and Sandwell (1988) and Kitchingham and Lai (2004). Agapova et al. (1979) based their assessment on existing bathymetric data and identified 7,080 seamounts over 1,000 m in elevation, including 302 flat-topped guyots. Using satellite altimetry data, Craig and Sandwell (1988) identified 8,556 seamounts having a diameter of at least 15 km. Kitchingman and Lai (2004) estimated the number of seamounts to be of 14,287 based on an analysis of the US Natioanl Oceanographic and Atmospheric Agency (NOAA) ETOPO2 raster bathymetric data set. These studies have mainly focussed on identifying individual seamount peaks. Global seamount basal area was also estimated by Etnoyer et al., (2010) and by Yesson et al., (2011). In the study by Harris et al. (2014), basal area of seamounts as well as summit morphology (i.e. distinguishing between ridges, guyots and seamounts) was mapped in order to produce a broad range of statistical measures of seamount geomorphology.
 ETOPO2 Global 2 minute elevations, 2001, National Geophysical Data Center, NOAA/NGDC, USA, www.ngdc.noaa.gov.