The great rift valleys of the earth took shape during the Pleistocene age, about two million years ago. They were caused mainly by volcanic eruptions powerful enough to split a mountain range, thus creating a rift between the two sides of the volcano.
Rift valleys are to be found in all parts of the world where volcanic action has been common. The most impressive example is the Great Rift Valley which extends from Jordan in south-west Asia to Mozambique in southern Africa. Many big lakes are situated within the valley’s boundaries.
Extremely steep edges are characteristics of these valleys. In Africa their edges rise to heights of 10,000 feet on either side.
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