| environ. | continental shelf The gently sloping seabed of the shallow water nearest to a continent, covering about 45 miles from the shore and deepening over the sloping sea floor to an average depth of 400 ft. It continues until it reaches the continental slope. The continental shelf contains most of the important fishing grounds and a range of resources, including gas and oil, sand and gravel. However, the shelf is, in general, a structural extension of the continent, and so may also be a source of minerals found in that region, such as tin, gold and platinum | piattaforma continentale |