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Rift Valley - A view from our expert author
The Great Rift Valley is the single largest geographical feature on the African continent, and was the only such feature visible to the first astronauts to reach the moon.
The Great Rift Valley is the single largest geographical feature on the African continent, and was the only such feature visible to the first astronauts to reach the moon. The process of rifting started some 20 million years ago along a 4,000km-long fault line that stretches from the Red Sea south to Mozambique’s Zambezi Valley. The gradual expansion of the valley has been accompanied by a large amount of volcanic activity: the floor is studded with dormant and extinct volcanoes such as Fantelle in Ethiopia and Longonot in Kenya. Africa’s two highest peaks, Mount Kilimanjaro and Mount Kenya, are also volcanic products of the rifting process, even though they lie outside of the Rift Valley. Millions of years from now, the Rift Valley will fill with ocean water, to split what is now Africa into two discrete land masses, much as happened millions of years ago when Madagascar was separated from the African mainland.
The Danakil Depression is one of the most striking features of the Great Rift Valley © Ariadne Van Zandbergen, Africa Image Library
The Ethiopian portion of the Rift Valley runs from the Red Sea to Lake Turkana on the Kenyan border. In northern Ethiopia, it forms the Danakil Depression, an inaccessible and inhospitable desert that dips to an altitude of 116m below sea level, one of the lowest points on the earth’s surface. South of the Danakil Depression, due east of Addis Ababa, the Rift narrows around Awash National Park to bisect the Ethiopian Highlands into the northwestern and southeastern massifs. In Ethiopia, as elsewhere along its length, the Rift Valley has formed an important barrier to animal movement and plant dispersal. For this reason, several animals are restricted to one or other side of the Rift, while populations of many animals that occur on both sides of the Great Rift, for instance Ethiopian wolves, form genetically distinct races.
The southern part of the Ethiopian Rift Valley is lower, warmer and drier than other densely populated parts of the country. Covered in acacia woodland and studded with lakes, it is also one of the few parts of Ethiopia that feels unequivocally African – in many respects the region is reminiscent of the Rift Valley lakes region of central Kenya. The six main lakes of the Ethiopian Rift formed during the last Ice Age, originally as two large lakes, one of which embraced what are now lakes Ziway, Abiata, Shala and Langano, the other lakes Abaya and Chamo.
South of Lake Chamo, the Rift Valley expands into the hot, barren scrublands of the Kenyan border region. The Rift here becomes less clearly defined, but it supports two further lakes, Chew Bahir and Turkana, both of which are practically inaccessible from the Ethiopian side (the vast bulk of Turkana’s surface area lies in Kenya). The Kenyan border area is most notable for two of Ethiopia’s most important national parks, Omo and Mago, which are among the most undeveloped game reserves in Africa, and noted not so much for their abundance of game (though most major plains animals are present) as for their wilderness atmosphere.
Although the Rift Valley is everywhere lower and hotter than the highlands, most of the lake region between Ziway and Arba Minch lies at an elevation of between 1,000m and 1,500m and temperatures are rarely uncomfortably hot. Rainfall figures are lower than in the highlands, but the pattern is broadly similar, with one long rainy season generally starting in April and finishing in July or August.