continental shelf

continental shelf, the shallow areas of sea fringing the continents underlain by rocks of continental origin. Across the shelf the seabed slopes gently offshore to a depth of about 200 metres (60 ft) to the shelf-break, where the seabed suddenly plunges into the deep ocean. Around Antarctica shelves are deeper, about 500 metres (1,640 ft), depressed by the vast weight of the ice shelf. Continental shelves are important regions. They are criss-crossed by shipping lanes, and local fisheries catch the vast majority of commercial fish there. The definition of what a shelf is has become critical during recent years as the exploitation of offshore oil and gas has extended. The wealth accruing from these resources within an Exclusive Economic Zone is internationally accepted as being vested in the state that borders the shelf. Defining the exact positions of offshore national boundaries has at times been highly contentious, has excited several clashes of interests between neighbouring states, and has exercised conferences of the United Nations Conference on the Law of the Sea for many sessions. For illus. see exclusive economic zone.

M. V. Angel