Relief

The 38th meridian dividesKenya into two halves of striking contrast. While the eastern half slopes gently to the coral-backed seashore, the western portion rises more abruptly through a series of hills andplateaus to the EasternRift Valley, known in Kenya as the Central Rift. West of the Rift is a westward-sloping plateau, the lowest part of which is occupied by Lake Victoria. Within this basic framework, Kenya is divided into the following geographic regions: theLake Victoria basin, the Rift Valley and associated highlands, the eastern plateau forelands, the semiarid and arid areas of the north and south, and the coast.

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The Lake Victoria basin is part of a plateau rising eastward from the lakeshore to the Rift highlands. The lower part, forming the lake basin proper, is itself a plateau area lying between 3,000 and 4,000 feet (900 and 1,200 metres) abovesea level. The rolling grassland of thisplateau is cut almost in half by the Kano Plain, into which an arm of the lake known asWinam Gulf (Kavirondo Gulf) extends eastward for 50 miles (80 km). The floor of the Kano Plain merges north and south into highlands characterized by a number of extinct volcanoes. These includeMount Elgon, rising to 14,178 feet (4,321 metres) at the Ugandan border on the extreme north of the basin.

TheRift Valley splits the highland region into two sections: theMau Escarpment to the west and theAberdare Range to the east. The valley itself is 30 to 80 miles (50 to 130 km) wide, and its floor rises from about 1,500 feet (450 metres) in the north around Lake Turkana (Lake Rudolf) to over 7,000 feet (2,100 metres) atLake Naivasha but then drops to 2,000 feet (600 metres) at the Tanzanian border in the south. The floor of theRift is occupied by a chain of shallow lakes separated by extinct volcanoes. Lake Naivasha is the largest of these; the others include LakesMagadi,Nakuru, Bogoria, andBaringo. West of the valley the diverse highland area runs from the thick lava block of the Mau Escarpment–Mount Tinderet complex northward to the Uasin Gishu Plateau. East of the Rift the Aberdare Range rises to nearly 10,000 feet (3,000 metres). The eastern highlands extend from the Ngong Hills and the uplands bordering Tanzania northward to the Laikipia Escarpment. Farther east they are linked by theNyeri saddle toMount Kenya, the country’s highest peak, at 17,058 feet (5,199 metres). The relief of both highlands is complex and includes plains, deep valleys, and mountains. Important in the historic and economic development of Kenya, the region was the focus of European settlement.

The eastern plateau forelands, located just east of the Rift highlands,constitute a vast plateau of ancient rocks gently sloping to the coastal plain. They are a region of scattered hills and striking elevated formations, the most prominent being the hills of Taita, Kasigau, Machakos, and Kitui. These hills, containing the area of more favourable climate, are surrounded by regions historically prone to famine.

The semiarid and arid areas in the north and northeast are part of a vast region extending from the Ugandan border through Lake Rudolf to the plateau area between the Ethiopian and Kenyan highlands. (The area fromLake Magadi southward, though not as arid, has the same characteristics.) Although tree and grass cover is scanty there, the areas of true desert are limited to the Chalbi Desert east of Lake Rudolf. The movement of people and livestock is strictly limited by the availability of water.

The coastal plain proper, which runs for about 250 miles (400 km) along theIndian Ocean, is a narrow strip only about 10 miles (16 km) wide in the south, but in theTana River lowlands to the north it broadens to about 100 miles (160 km). Farther northeast it merges into the lowlands of Somalia. The excellent natural harbours include that ofMombasa, which is one of the best in East Africa.

Drainage

Kenya’s drainage pattern originated when a large oval dome of rock arose in the west-central part of the country and created the Central Rift. This dome produced a primeval watershed from which rivers once drained eastward to the Indian Ocean and westward to theCongo River system and theAtlantic Ocean. Still following this ancient pattern are theTana and Galana rivers, which rise in the eastern highlands and flow roughly southeast to the Indian Ocean. West of the Central Rift, however, the major streams now drain into Lake Victoria. These include the Nzoia, Yala, Mara, and Nyando rivers. Between the eastern and western systems, the rifting of the dome’s crust has created a complex pattern of internal streams that feed the major lakes.

There are no major groundwaterbasins, and, apart from the Tana River, most of the rivers in Kenya are short and often disappear during the dry season. Lake Victoria, with a surface area of 26,828 square miles (69,484 square km), is the largest lake in Africa, the second largest freshwater body in the world, and a major reservoir of theNile River.Lake Rudolf, some 150 miles (240 km) long and 20 miles (30 km) wide, is the largest of the country’s Rift Valley lakes. Other lakes are rather small, and their surface areas fluctuate considerably.

Soils

In the Lake Victoria basin, lava deposits have produced fertile and sandy loam soils in the plateaus north and south of Winam Bay, while the volcanic pile ofMount Elgon produces highly fertile volcanic soils well known for coffee and tea production. The Rift Valley and associated highlands are composed of fertile dark brown loams developed on younger volcanic deposits.

The most widespread soils in Kenya, however, are the sandy soils of the semiarid regions between the coast and the Rift highlands. To the north of the Rift are vast areas covered by red desert soils, mainly sandy loams. Kenya’s soils are subject to widespread erosion largely because of the lack of forest cover; overgrazing and cultivation, especially in the arid and semiarid regions, also contribute to soil loss.