(2) Continental Shelf Explanation: The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas (known as shelf seas) and gulfs, and was almost similarly submerged during other interglacial periods. 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 or seaiment at the base of the slope, called the continental rise.