British East Africa, a term, in its widest sense, including all the territory under British influence on the eastern side of Africa between German East Africa on the south and Abyssinia and the Anglo-Egyptian Sudan on the north. It comprises the protectorates of Zanzibar, Uganda and East Africa. Apart from a narrow belt of coastland, the continental area belongs almost entirely to the great plateau of East Africa, rarely falling below an elevation of 2000 ft., while extensive sections rise to a height of 6000 to 8000 ft. From the coast lowlands a series of steps with intervening plateaus leads to a broad zone of high ground remarkable for the abundant traces of volcanic action. This broad upland is furrowed by the eastern "rift-valley," formed by the subsidence of its floor and occupied in parts by lakes without outlet. Towards the west a basin of lower elevation is partially occupied by Victoria Nyanza, drained north to the Nile, while still farther inland the ground again rises to a second volcanic belt, culminating in the Ruwenzori range. (See Zanzibar, and for Uganda protectorate see Uganda.) The present article treats of the East Africa protectorate only.
The southern frontier, coterminous with the northern frontier of German East Africa, runs north-west from the mouth of the Umba river in 4° 40′ S. to Victoria Nyanza, which it strikes at 1° S., deviating, however, so as to leave Mount Kilimanjaro wholly in German territory. The eastern boundary is the Indian Ocean, the coast line being about 400 m. On the north the protectorate is bounded by Abyssinia and Italian Somaliland; on the west by Uganda. It has an area of about 240,000 sq. m., and a population estimated at from 2,000,000 to 4,000,000, including some 25,000 Indians and 3000 Europeans. Of the Europeans many are emigrants from South Africa; they include some hundreds of Boer families.
The first of the parallel zones - the coast plain or "Temborari" - is generally of insignificant width, varying from 2 to 10 m., except in the valleys of the main rivers. The shore line is broken by bays and branching creeks, often cutting off islands from the mainland. Such are Mvita or Mombasa in 4° 4′ S., and the larger islands of Lamu, Manda and Patta (the Lamu archipelago), between 2° 20′ and 2° S. Farther north the coast becomes straighter, with the one indentation of Port Durnford in 1° 10′ S., but skirted seawards by a row of small islands. Beyond the coast plain the country rises in a generally well defined step or steps to an altitude of some 800 ft., forming the wide level plain called "Nyika" (uplands), largely composed of quartz. It contains large waterless areas, such as the Taru desert in the Mombasa district. The next stage in the ascent is marked by an intermittent line of mountains - gneissose or schistose - running generally north-north-west, sometimes in parallel chains, and representing the primitive axis of the continent. Their height varies from 5000 to 8000 ft.
Farther inland grassy uplands extend to the eastern edge of the rift-valley, though varied with cultivated ground and forest, the former especially in Kikuyu, the latter between 0° and 0° 40′ S. The most extensive grassy plains are those of Kapte or Kapote and Athi, between 1° and 2° S. The general altitude of these uplands, the surface of which is largely composed of lava, varies from 5000 to 8000 ft. This zone contains the highest elevations in British East Africa, including the volcanic pile of Kenya (q.v.) (17,007 ft.), Sattima (13,214 ft.) and Nandarua (about 12,900 ft.). The Sattima (Settima) range, or Aberdare Mountains, has a general elevation of fully 10,000 ft. To the west the fall to the rift-valley is marked by a line of cliffs, of which the best-defined portions are the Kikuyu escarpment (8000 ft.), just south of 1° S., and the Laikipia escarpment, on the equator. One of the main watersheds of East Africa runs close to the eastern wall of the rift-valley, separating the basins of inland drainage from the rivers of the east coast, of which the two largest wholly within British East Africa are the Sabaki and Tana, both separately noticed. The Guaso Nyiro rises in the hills north-west of Kenya and flows in a north-east direction.
After a course of over 350 m. the river in about 1° N., 39° 30′ E. is lost in a marshy expanse known as the Lorian Swamp.
The rift-valley, though with a generally level floor, is divided by transverse ridges into a series of basins, each containing a lake without outlet. The southernmost section within British East Africa is formed by the arid Dogilani plains, drained south towards German territory. At their north end rise the extinct volcanoes of Suswa (7800 ft.) and Longonot (8700), the latter on the ridge dividing off the next basin - that of Lake Naivasha. This is a small fresh-water lake, 6135 ft. above the sea, measuring some 13 m each way. Its basin is closed to the north by the ridge of Mount Buru, beyond which is the basin of the still smaller Lakes Nakuro (5845 ft.) and Elmenteita (5860 ft.), followed in turn by that of Lakes Hannington and Baringo (q.v.). Beyond Baringo the valley is drained north into Lake Sugota, in 2° N., some 35 m. long, while north of this lies the much larger Lake Rudolf (q.v.), the valley becoming here somewhat less defined.
On the west of the rift-valley the wall of cliffs is best marked between the equator and 1° S., where it is known as the Mau Escarpment, and about 1° N., where the Elgeyo Escarpment falls to a longitudinal valley separated from Lake Baringo by the ridge of Kamasia. Opposite Lake Naivasha the Mau Escarpment is over 8000 ft. high. Its crest is covered with a vast forest. To the south the woods become more open, and the plateau falls to an open country drained towards the Dogilani plains. On the west the cultivated districts of Sotik and Lumbwa, broken by wooded heights, fall towards Victoria Nyanza. The Mau plateau reaches a height of 9000 ft. on the equator, north of which is the somewhat lower Nandi country, well watered and partly forested. In the treeless plateau of Uasin Gishu, west of Elgeyo, the land again rises to a height of over 8000 ft., and to the west of this is the great mountain mass of Elgon (q.v.). East of Lake Rudolf and south of Lake Stefanie is a large waterless steppe, mainly volcanic in character, from which rise mountain ranges. The highest peak is Mount Kanjora, 6900 ft. high. South of this arid region, strewn with great lava stones, are the Rendile uplands, affording pasturage for thousands of camels.
Running north-west and south-east between Lake Stefanie and the Daua tributary of the Juba is a mountain range with a steep escarpment towards the south. It is known as the Goro Escarpment, and at its eastern end it forms the boundary between the protectorate and Abyssinia. South-east of it the country is largely level bush covered plain, mainly waterless.
[Geology. - The geological formations of British East Africa occur in four regions possessing distinct physiographical features. The coast plain, narrow in the south and rising somewhat steeply, consists of recent rocks. The foot plateau which succeeds is composed of sedimentary rocks dating from Trias to Jurassic. The ancient plateau commencing at Taru extends to the borders of Kikuyu and is composed of ancient crystalline rocks on which immense quantities of volcanic rocks - post-Jurassic to Recent - have accumulated to form the volcanic plateau of Central East Africa.
The formations recognized are given in the following table: -
1. Alluvium and superficial sands.
2. Modern lake deposits, living coral rock.
3. Raised coral rock, conglomerate of Mombasa Island.
4. Gravels with flint implements.
5. Glacial beds of Kenya
6. Shales and limestones of Changamwe.
7. Flags and sandstones.
8. Grits and shales of Masara and Taru.
9. Shales of the Sabaki river.
10. Schists and quartzites of Nandi.
11. Gneisses, schists, granites.
Igneous and Volcanic.
Active, dormant and extinct volcanoes.
Post-Jurassic to Pleistocene
Kibo and volcanoes of the rift-valley.
Kimawenzi, Kenya and plateau eruptions.