Submarine fans – Fans are “a relatively smooth, fan-like, depositional feature normally sloping away from the outer termination of a canyon or canyon system” (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).

Sediment transported down submarine canyons is deposited to form submarine fans at the mouth of the canyon where the seabed flattens out adjacent to the deep ocean floor.  Submarine fans and other sediment deposits, located at the foot of the continental slope especially along passive continental margins, accumulate over time to form a gently-dipping ramp composed of land-derived sediment (Walker, 1992).  Currents flowing along the foot of the slope (referred to as contour currents because they flow parallel to an isobath-contour line) can transport the sediments delivered by canyons along-slope to form large sediment drifts.  Hence, 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.

Submarine fans (in red) overlie the continental rise (in yellow) and are formed by thick sediment deposits adjacent to passive continental margins.  The world’s largest submarine fan is located in the Bay of Bengal, northern Indian Ocean, which is supplied with sediment by the Ganges-Brahmaputra River system.

Statistics of submarine fans (after Harris et al., 2014).  The percentage areas refer to fraction of ocean regions that is submarine fan.

OceanArea km2Fan area%Number of FansAverage Fan area km2
Arctic Ocean152,2701.171113,840
Indian Ocean4,342,9106.0912361,910
Mediterranean and Black Sea 165,8305.491312,760
North Atlantic Ocean1,325,5202.963340,170
North Pacific Ocean236,5300.288356,760
South Atlantic Ocean895,6402.211849,760
South Pacific Ocean25,5600.029346,390
Southern Ocean1,158,8905.702644,570
All Oceans8,303,1602.2915154,990

Covault , J.A., 2011. Submarine Fans and Canyon-Channel Systems: A Review of Processes, Products, and Models. Nature Education Knowledge 3, 893-894.

Curray, J.R., Emmel, F.J., Moore, D.G., 2002. The Bengal Fan: morphology, geometry, stratigraphy, history and processes. Marine and Petroleum Geology 19, 1191–1223.

Divins, D., 2003. Total Sediment Thickness of the World’s Oceans & Marginal Seas. NOAA National Geophysical Data Center.

Dowdeswell, J.A., Cofaigh, C., Noormets, R., Larter, R.D., Hillenbrand, C.D., Benetti, S., Evans, J., Pudsey, C.J., 2008. A major trough-mouth fan on the continental margin of the Bellingshausen Sea, West Antarctica: The Belgica Fan. Marine Geology 252, 129-140.

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.

Walker, R.G., 1992. Turbidites and submarine fans, in: Walker, R.G., James, N.P. (Eds.), Facies Models – response to sea level change, Second ed. Geological Association of Canada, St. John’s, Newfoundland, Canada, pp. 239-263.