Abyssal basins and the polar seas

Abyssal plains and basins are traditionally defined as areas of the deep-ocean floor in which the seabed is flat, with a slope of less than 1°, and deeper than 4,500 meters. They were not recognized as distinct physiographic features until the late 1940s, and there have been very few systematic investigations of limited areas. As a result, they are among the least known areas of the Earth’s surface. The examples presented in the

Handbook of Seafloor Sonar Imagery

(Blondel and Murton, 1997) came mostly from a single sonar (TOBI, 30 kHz) and from a single world-leading team at the National Oceanography Centre (U.K.). Many new results have been published in the decade since by several research groups around the world and the most representative examples will be presented in this chapter (Sections 6.3 and 6.5).