The continental shelf is an underwater landmass which extends from a continent, resulting in an area of relatively shallow water known as a shelf sea.

Much of the shelves were exposed during glacial periods and interglacial periods. The slope of the shelf is usually quite low, on the order of 0.5°

The shelf surrounding an island is known as an insular shelf.

The continental margin, between the continental shelf and the abyssal plain, comprises a steep continental slope followed by the flatter continental rise.

Sediment from the continent above cascades down the slope and accumulates as a pile of sediment at the base of the slope, called the continental rise.

Extending as far as 500 km from the slope, it consists of thick sediments deposited by turbidity currents from the shelf and slope. The continental rise’s gradient is intermediate between the slope and the shelf, on the order of 0.5–1°.

Under the United Nations Convention on the Law of the Sea, the name continental shelf was given a legal definition as the stretch of the seabed adjacent to the shores of a particular country to which it belongs.

The largest shelf – the Siberian Shelf in the Arctic Ocean – stretches to 1,500 kilometers (930 mi) in width.

The continental shelf is considered to be the flooded margins of the continent and not a proper part of the deep ocean basin.

Exploration of minerals and hydrocarbons.

The relatively accessible continental shelf is the best understood part of the ocean floor. Most commercial exploitation from the sea, such as metallic-ore, non-metallic ore, and hydrocarbon extraction, takes place on the continental shelf.

Sovereign rights over their continental shelves up to a depth of 200 metres or to a distance where the depth of waters admitted of resource exploitation were claimed by the marine nations that signed the Convention on the Continental Shelf drawn up by the UN’s International Law Commission in 1958.

This was partly superseded by the 1982 United Nations Convention on the Law of the Sea which created the 200 nautical mile exclusive economic zone and extended continental shelf rights for states with physical continental shelves that extend beyond that distance.

The legal definition of a Continental shelf under UNCLOS

The legal definition of a continental shelf differs significantly from the geological definition.

UNCLOS states that the shelf extends to the limit of the continental margin, but no less than 200 nautical miles from the baseline.

Thus inhabited volcanic islands such as the Canaries, which have no actual continental shelf, nonetheless have a legal continental shelf, whereas uninhabitable islands have no shelf.