Abyssal mountains – Mountains on the seafloor at abyssal depths having a vertical relief of greater than 1,000 m within a search radius of ~25 km are termed “abyssl mountains” (Harris et al., 2014).  They include discrete guyots, seamounts, ridges (classes that are superimposed over “mountains”) and other positive relief features.

Abyssal classification categories (after Harris et al., 2014).  The percentage areas first line refers to percentage of ocean basin area and the second line (in brackets) refers to percentage of abyssal area.

OceanAbyssal Plain Area km2Abyssal Plain Area%Abyssal Hills Area km2Abyssal Hills Area %Abyssal Mountains Area km2Abyssal Mtns. Area %
Arctic Ocean Abyssal2,068,57015.9 (38.7)2,244,92017.3 (42)1,036,0607.98 (19.4)
Indian Ocean Abyssal21,772,79030.5 (34.7)30,179,17042.3 (48)10,859,50015.2 (17.3)
Mediterranean and Black Sea - Abyssal612,87020.3 (43.6)613,83020.3 (43.7)179,2205.93 (12.7)
North Atlantic Ocean Abyssal10,255,54022.9 (30.4)16,477,47036.8 (48.9)6,987,83015.6 (20.8)
North Pacific Ocean Abyssal24,906,63030.4 (36.2)29,676,23036.2 (43.2)14,137,99017.3 (20.6)
South Atlantic Ocean Abyssal10,033,65024.8 (27.4)19,511,51048.3 (53.3)7,031,56017.4 (19.2)
South Pacific Ocean Abyssal22,648,40026 (28)44,059,80050.6 (54.4)14,299,47016.4 (17.7)
Southern Ocean Abyssal8,565,27042.1 (50.4)6,688,37032.9 (39.3)1,749,8408.6 (10.3)
All Oceans All Abyssal100,863,73027.9 (32.9)149,451,31041.3 (48.7)56,281,46015.6 (18.4)

Harris, P.T., MacMillan-Lawler, M., Rupp, J., Baker, E.K., 2014. Geomorphology of the oceans. Marine Geology 352, 4-24.

IHO, 2008. Standardization of Undersea Feature Names: Guidelines Proposal form Terminology, 4th ed. International Hydrographic Organisation and Intergovernmental Oceanographic Commission, Monaco, p. 32. http://www.iho.int/iho_pubs/bathy/B-6_e4_EF_Nov08.pdf