Abstract

The study of the distribution of elevations on the Earth or hypsography shows how more than half of the world ocean is dominated by deep basins (4–6.5 km) covered with abyssal plains and hills. Seafloor from 2 to 4 km depth is primarily comprised of oceanic ridge systems that spread over ~30% of the seafloor. The shallow seas and continental margins from sea level to 2 km depth cover the least amount of area and represent only ~15% of the seafloor. Superimposed on the primary features of the seafloor landscape are secondary features such as the median valley, seamounts, and submarine canyons. Fine-scale geomorphology of the underwater landscape and discontinuities in bathymetry are increasingly being used to assess distributions of marine organisms. New terminology and computational methods identify seafloor features that enhance marine biodiversity and allow for better management of vulnerable marine ecosystems.