Great Rift Valley

The Great Rift Valley is an enormous geographical feature caused by the separation of the African and Eurasian tectonic plates around 35 million years ago. It was named by the explorer John Walter Gregory[?].

The feature runs over 5000 km, from the Dead Sea in Syria to Mozambique. The valley varies in width from 30-100 km and in depth from a few hundred to several thousand metres. In eastern Africa the valley splits into two, the Eastern Rift[?] and the Western Rift[?].

The Western Rift contains some of the deepest lakes in the world (up to 560 metres deep) including Lake Tanganyika. Lake Victoria, the second largest lake in the world, is considered part of the Rift Valley system.

In Kenya the valley is deepest to the north of Nairobi. As the valley has no outlet to the sea, its lakes tend to be shallow and have a high mineral content as the evaporation of water leaves the salts behind. For example, Lake Magadi[?] is almost solid soda (sodium carbonate), and Lake Elmenteita[?], Lake Baringo, Lake Bogoria[?], and Lake Nakuru[?] are all strongly alkaline, while Lake Naivasha[?] needs to be supplied by freshwater springs to support its biological variety.

The formation of the Rift Valley is currently ongoing. In a few million years, eastern Africa will probably split off to form a new landmass. The original activity that caused the Rift weakened the Earth's crust. The area is therefore volcanically and seismically active, producing the volcanoes Mount Kilimanjaro, Mount Kenya[?], Mount Meru, and Mount Elgon[?], and the Crater Highlands[?] in Tanzania.

The Rift Valley has been a rich source of anthropological discovery. The bones of several hominid ancestors of modern humans have been found there, including those of "Lucy", a nearly complete australopithecine skeleton, which was discovered by anthropologist Donald Johanson. Richard and Maeve Leakey[?] have also done significant work in this region.