The Great Rift Valley is the continuous geographic trough, about 6,000 km long, that cuts through Africa and runs from Syria in North West Asia to Mozambique in Eastern Africa. The name was given by the late 19th century explorer John Walter Gregory. Scientists say that the Rift Valley was formed about 20 million years ago when the earth’s crust weakened and tore itself apart creating the jagged rift across the African continent. During this phenomenon, great volcanic mountains were formed by eruptions on either side of the valley, while the valley floor gradually sank into the flat plain as it is known today.
The Great Rift Valley divides Kenya down the length of the country. The width varies from about 100 km to its narrowest width of about 45 km just north of Nairobi. The depth of the valley floor also varies, being at the lowest near the Lake Turkana. Apart from the Rift Valley itself, the area has other important geographic features such as the extinct volcanoes, Mount Longonot and Mount Suswa, Lake Baringo, Lake Bogoria, Lake Magadi, Lake Nakuru, Lake Naivasha, the Suguta Valley and Lake Turkana.
Rift Valley covers an area of 173,854 km2 (42,960,000 acres), and has 13 counties namely; Turkana, West Pokot, Samburu, Trans-nzoia, Uasin Gishu, Elgeyo Marakwet, Nandi, Baringo, Laikipia, Nakuru, Kajiado, Kericho and Bomet.