Sunda shelf
Geologically, the Sunda Shelf is a southeast extension of the continental shelf of Southeast Asia. Major landmasses on the shelf include the Malay Peninsula, Sumatra, Borneo, Java, Madura, Bali and their surrounding smaller islands. It covers an area of approximately 1.85 million km2. Sea depths over the shelf rarely exceed 50 metres and extensive areas are less than 20 metres resulting in strong bottom friction and strong tidal friction. Steep undersea gradients separate the Sunda Shelf from the Philippines, Sulawesi, and the Lesser Sunda Islands.
Biogeographically, Sundaland is a term for the region of Southeastern Asia which encompasses these areas of the Asian continental shelf that were exposed during the last ice age. Sundaland included the Malay Peninsula on the Asian mainland, as well as the large islands of Borneo, Java, and Sumatra and their surrounding islands. The same steep undersea gradients that mark the eastern boundary of Sundaland are identified biogeographically by the Wallace Line, identified by Alfred Russel Wallace, which marks the eastern boundary of the Asia's land mammal fauna, and is the boundary of the Indomalaya and Australasia ecozones.
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