caused the South China Sea to open. This view is disputed by geologists who do not consider Indochina to have moved far relative to mainland Asia. Marine geophysical studies in the Gulf of Tonkin by Peter Clift has shown that the Red River Fault was active and causing basin formation at least by 37 million years ago in the NW South China Sea, consistent with extrusion playing a part in the formation of the sea. Since opening the South China Sea has been the repository of large sediment volumes delivered by the Mekong River, Red River and Pearl River. Several of these deltas are rich in oil and gas deposits. Islands and seamounts The South China Sea contains over 250 small islands, atolls, cays, shoals, reefs, and sandbars, most of which have no indigenous people, many of which are naturally under water at high tide, and some of which are permanently submerged. The features are: The Spratly Islands The Paracel Islands Pratas Island and the Vereker Banks The Macclesfield Bank The Scarborough Shoal The Spratly Islands spread over an 810 by 900 km area covering some 175 identified insular features, the largest being Taiping Island (Itu Aba) at just over long and with its highest elevation at . The largest singular feature in the area of the Spratly Islands is a wide seamount called Reed Tablemount, also known as Reed Bank, in the northeast of the group, separated from Palawan Island of the Philippines by the Palawan Trench. Now completely submerged, with a depth of , it was an island until it sank about 7,000 years ago due to the increasing sea level after the last ice age. With an area of , it is one of the largest submerged atoll structures in the world. Trade route The South China Sea is an extremely significant body of water in a geopolitical sense. The sea has historically been an important trade route between China, southeast Asia, and going to India and the west. A number of shipwrecks of trading ships that lie on the ocean's floor attest to a thriving trade going back centuries. Nine historic trade ships carrying ceramics dating back to the 10th century until the 19th century were excavated under Swedish engineer Sten Sjöstrand. Today it is the second most used sea lane in the world, while in terms of world annual merchant fleet tonnage, over 50% passes