continentalmargin

Continental margin is the zone of the seafloor that surrounds a continent and marks the transition from continental crust to oceanic crust. It is the submerged edge of a continent and comprises three main morphologic zones: the continental shelf, the continental slope, and the continental rise, which leads to the deep ocean basin. The shelf extends from the coastline to the shelf break, where the gradient steepens into the slope. The rise accumulates sediment delivered from the land, often via turbidity currents that form submarine fans on the basin plain. The boundary with the open ocean is at the end of the rise or where thick sediment packages transition to pelagic deposition in the abyssal plain.

Margins are classified as passive or active. Passive margins occur along trailing edges of continents, away from plate boundaries, and are characterized by broad shelves, extensive sedimentation, and relatively little tectonic activity. Active margins lie near convergent or transform plate boundaries, feature narrow or absent shelves, steep slopes, and significant tectonic uplift or subsidence and nearby trenches.

Formation and processes include tectonic setting, sediment supply from rivers, glacial and eolian contributions, and oceanographic processes such as turbidity currents that transport sediments down the slope. Sea-level fluctuations repeatedly rework the margin and shift the position of the shelf break. Submarine canyons and deep-sea fans develop on the slope and rise. The margins host important natural resources, especially hydrocarbons on many passive margins, and support biodiversity and fisheries along their shelves.

Examples include the eastern margins of North America and western Africa (passive margins) and the western margins of South America and parts of the western Pacific (active margins). The continental margin thus represents the continental-to-ocean transition that shapes continental geology, oceanography, and resource distribution.