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The historical geography of East Africa and the Great Rift Valley

Posted in Africa, Anthropology, Exploration, Geography, Historical articles, History, Wildlife on Monday, 30 July 2012

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This edited article about East Africa originally appeared in Look and Learn issue number 756 published on 10th July 1976.

Stanley meets Livingstone, picture, image, illustration

H M Stanley found Dr Livingstone living near the shores of Lake Tanganyika in East Africa by Severino Baraldi

Once a favourite field of adventure for explorers who took their lives in their hands; now the home of newly emergent nations, and a paradise for tourists and naturalists – that is East Africa. It owes its special character largely to a geological “accident”.

Most of Africa originally consisted of a vast plateau. This can be recognised even now from a relief map; though the huge tableland has been cut by rivers, and at various points, especially round the rim, mountains have appeared.

At one point in time there was an exceptionally violent disturbance of the pattern in the east, as can be seen by the tangled network of mountains, valleys and lakes that exist there. This extends about 2,000 miles (3,200 km) from north of the Zambezi River as far as the Red Sea coast.

This subterranean disturbance caused deep faults, or fractures, in the rock strata. When two such faults happen to run parallel, or approximately so, the earth’s crust between them tends to sink as a solid block, while the broken edges on either side frequently tilt upwards. In this manner a deep, steep-sided valley is formed, known as a “rift valley”.

The Great Rift Valley which is such a striking feature of East Africa is not really a single valley, despite its name. Nor is it confined to Africa. The Red Sea itself is part of the system, and it continues northwards, through the Gulf of Akaba, to the valleys of the Dead Sea and the Jordan River, on Israel’s eastern borders.

East Africa’s Great Rift Valley is far from being a straight and simple formation. From the Red Sea it runs southwards, splitting the highlands of Ethiopia. Then it divides into two branches. Lake Rudolf fills the northern part of the east branch, which runs south through Kenya and Tanganyika. Its course is marked by a chain of comparatively small lakes, and flanked on the east by the towering peaks of Mounts Kenya and Kilimanjaro. These are so high as to be snow-capped, even though Mount Kenya lies on the equator. The east branch valley finally rejoins the main rift valley at Lake Malawi (formerly known as Lake Nyasa).

The western branch is far more sharply defined, and more continuous in formation. It forms a sweeping curve north from Lake Malawi, and its bottom is almost entirely filled by long, narrow lakes of great depth. Biggest of these is Lake Tanganyika, 400 miles (640 km) in length.

The upheaval that gave birth to the Great Rift Valley was probably accompanied, and certainly followed, by widespread volcanic eruptions. Most of the high mountains of the region, including Kilimanjaro and Kenya, are extinct volcanoes. Many hills and craters appeared in the floors of the valleys. This part of Africa is still subject to earthquakes, and to some volcanic activity.

The volcanic disturbances and the continuous erosion by wind, rain, and river, have done much to blur the original clear outlines of the rifts. But in many areas they are still plainly visible.

Typical of the breath-taking views to be seen in the rift country is the one that awaits a motorist driving north from Nairobi to Nakuru, in Kenya. The road passes close to the edge of the escarpment that here forms the wall of the rift’s eastern branch. It drops almost vertically to the flat valley bottom, which stretches away into the distance to the far escarpment, forming a dim backcloth some forty miles away.

This part of the Great Rift Valley is given over mainly to farming. Better known to the outside world are those areas, in both the western and the eastern branches, which afford a refuge for Africa’s diminishing wild-life, and where efforts are being made to protect its future. Elephant and rhinoceros, lion and leopard, giraffe, zebra and many species of antelope are among the many creatures which owe their survival to such measures – though their future is still in danger.

One of the preservation areas is Lake Manyara, in Tanzania. Here flamingoes can be seen rising from the water in a rose pink cloud. So numerous are they that they have to “queue up” in their thousands, waiting for surface space for their take-off. On the shores of the lake, elephant, rhinoceros and other big game are seen.

The waters of the lakes are rich in fish. In Lake Rudolf 100-pound specimens of the Nile perch species are not unusual. The fish harvests of the lakes are still the principal food source of many tribes in East Africa.

Crocodiles, too, make their home in the lakes. They also are threatened – by the hunters who seek their valuable skins. The lumbering hippopotamus is a denizen of the shallows. A channel between Lake Albert – most northerly of the western lakes – and Lake George is said to be the haunt of the largest of all colonies of hippos, numbering several thousand.

Vegetation naturally varies somewhat throughout the rift region. Some parts of the valley floors are almost barren. Elsewhere there may be trees and comparatively thick bush. But much of the land is of the type known as “savannah”, with coarse grasses and scattered small trees and thorn scrub.

The Great Rift Valley country has provided a setting for many famous events. It was on the shore of Lake Tanganyika that Henry M. Stanley found Dr. David Livingstone in 1871 – after the famous explorer-missionary had been missing for three years.

The region was the scene of protracted warfare between British and German forces in the First World War. More recently it has seen the birth of several new independent states.

Discoveries in the last few years have shown that the Great Rift Valley’s association with the story of the human race is vastly more ancient than anyone once thought. Four years ago fragments of a human-type skull were unearthed from volcanic ash on the eastern shore of Lake Rudolf. Tests showed them to be nearly three million years old – though it had previously been thought that Man had existed for only half a million years or less. This upset to old theories was later underlined by the discovery of still older remains in Ethiopia.

It seems that the convulsions which carved great gashes in the face of eastern Africa not only gave the continent spectacular scenery. They may also have fashioned the birthplace of mankind.

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