administrative region, northern Tanzania, East Africa. Established in 1963, it has an area of about 33,250 square miles (86,100 square km), including 950 square miles (2,460 square km) of water area. It is bordered on the north by Kenya. The Serengeti Plain lies in the northwest, and the Masai Steppe, broken only by isolated gneiss hills, lies in the south. In the central area of the region are the Crater Highlands, bordering portions of the East African Rift System. Volcanic activity and faulting have created broad lava plains and volcanic massifs such as Mount Meru (14,979 feet [4,566 metres]) and the occasionally active Oldoinyo Lengai (9,442 feet [2,878 metres]). Rainfall varies from 70 inches (1,800 mm) annually on Mount Meru to 20 inches (508 mm) on the semiarid plains. Terrain ranges from wooded savannas and montane forests to alpine areas
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