Ethiopian Plateau

Ethiopian Plateau 

(also Amhara Plateau), a tableland in northeastern Africa, primarily in Ethiopia. The Ethiopian Plateau extends from Lake Turkana to the lower course of the Barka River—that is, from 5° to 18° N lat. Elevations increase from 2,000 m in the southwest to 3,000 m in the northeast. The tableland drops off abruptly in the east and descends in steps in the west.

The northern part of the Ethiopian Plateau (to 15° N lat.) is a peneplain formed on crystalline rocks, with isolated mountain peaks; to the south are mesa-like lava plateaus, known as ambas, that are separated by deep canyon-like valleys into massifs difficult of access. The highest peak is Ras Dashan (4,623 m) in the Semien Mountains. Southwest of the mountains is a vast inter-montane depression that includes Lake Tana. In the southeast the tableland descends in steps to a deep fault depression that forms the border of the Somali Plateau. Transverse lava sheets divide the depression into several basins; fumaroles and hot springs are found on its floor and along its periphery.

The tableland has a hot, subequatorial climate, with a wet summer. A marked altitudinal zonation of climate, soils, and vegetation is observed. The climates of the western and eastern slopes differ sharply. The western slopes receive abundant precipitation in the summer and about 1,500 mm annually. In summer, hot winds similar to foehns often move down the eastern slopes, which are dry; precipitation (about 500 mm annually) falls primarily in winter. High in the mountains there are winter snowfalls.

The Ethiopian Plateau has an extensive river network. The large rivers of the Nile-Blue Nile, Atbara, and Baro basins, which flow through deep canyons, have many rapids and are not navigable.

The soil and vegetation zones are most highly developed on the windward western slope. The lowest zone—the quolla (to 1,700–1,800 m)—has an average annual temperature of at least 20°C, with tropical rain forests and, on the interfluvial benches, high-grass and dry (in the north) savannas. In the woina dega zone (to 2,400 m) average monthly temperatures range from 13° to 16–18°C; there is savanna vegetation, with palms, acacias, and Euphorbia candelabrum. In the dega zone (2,400–4,000 m), where temperatures drop sharply, coniferous forests of juniper trees grow on the mountain slopes, giving way to high-mountain steppes. The three zones have long been cultivated and produce many varieties of grain crops, notably durum wheat, rye, and barley. Maize, oil-bearing plants, citrus trees, and coffee trees are also cultivated.

The fauna of the Ethiopian Plateau is quite diverse, with such herbivores as giraffes, elephants, zebras, and antelope and such predators as the leopard, Senegalese lion, lynx, and hyena. Rhinoceroses and hippapotamuses live near the rivers. The numerous apes include green monkeys, geladababoons, and anubis baboons. The bird life is especially rich and diverse.