African Rift Valley: Formation & Overview

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  • 0:34 Formation
  • 1:18 East African Rift System
  • 3:25 Diversity
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Lesson Transcript
Instructor: Jordana LaFantasie

Jordge teaches college Biology, Ecology and Environmental Science. She has a Doctorate degree in Agronomy.

This lesson offers a definition and description of rift valleys and their formation with details focusing on the East African Rift System. The diversity of the region is discussed, as well as its status as the 'Cradle of Mankind.'

What Is a Rift Valley?

A rift valley can be defined as a valley that is created by the splitting of the earth's crust. Rift valleys differ from river or glacial valleys in that they are created by tectonic activity rather than surface climatic forces.They are often narrow with flat floors and steep walls, and most of them occur in oceanic crust. Two major rift valleys occur on the land surface, or in the continental crust: the Baikal Rift Valley in Siberia and the African Rift.


We've established that rift valleys are formed due to a splitting in the earth's crust. How does that happen? The earth's crust is constantly reforming due to the movement of tectonic plates. Tectonic plates are sections of the earth's surface layer, or crust and upper mantle that move on the currents of the underlying mantle.

The plates may be driven together at the edges to create mountain ranges (such as the Himalaya Mountain Range), or one plate may slide under the other, often causing volcanic activity. Plates often slide against one another, building tremendous pressure that causes earthquakes. Or, the plates may be pulling apart from one another; this is what creates a rift valley.

East African Rift System

The African Rift, also known as the East African Rift System (or EARS), is actually a system of rifts created by the separating of the Nubian Plate and the Somalian Plate , which together comprise the African Plate of the African continent. The following is a map of East Africa showing historically important volcanoes as red triangles and the separating of the Somalian and Nubian sections of the African Plate.

The system began developing during the Miocene (22-25 million years ago) and stretches thousands of kilometers across Tanzania, Kenya, Ethiopia, the East African Great Lakes, and beyond into the Red Sea and Gulf of Aden. So, although we tend to think of the African Rift as one rift valley, it is actually a complex series of related rifts.

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