The Great Rift Valley of Ethiopia, (or Main Ethiopian Rift) is a branch of the East African Rift that runs through Ethiopia in a southwest direction from the Afar Triple Junction. In the past, it was seen as part of a "Great Rift Valley" that ran from Madagascar to Syria.
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The Great Rift Valley lies between the Ethiopian Plateau to the north and the Somalian Plateau to the south. The rift developed as the Nubian and Somalian plates began to separate about 25 million years ago along the East African rift system. Rifting along the Ethiopian rift valley began at the south end around 18 million years ago, extending northward to reach and form the Afar triple junction about 11 million years ago. The rift is extending in an ESE-WNW direction at about 2.5 millimetres (0.098 in) annually.[1]
The Ethiopian rift valley is about 84 kilometres (52 mi) wide and bordered on both margins by large, discontinuous normal faults which began developing during the Miocene Period and are now thought to be inactive. The currently active rift consists of a series of smaller en echelon, right-stepping, rift basins of Quaternary to recent age. These basins are about 20 kilometres (12 mi) wide and 60 kilometres (37 mi) long. Extension within the valley is now thought to be mainly along these faulted and magmatically active segments. These segments are considered to be developing mid ocean ridge spreading centers.[1][2]
The Ethiopian Rift Valley lakes are the northernmost of the African Rift Valley lakes. The Ethiopian Rift Valley lakes occupy the floor of the rift valley between the two highlands. Most of the Ethiopian Rift Valley lakes do not have an outlet, and most are alkaline. Although the Ethiopian Rift Valley Lakes are of great importance to Ethiopia's economy, as well as being essential to the survival of the local people, there were no intensive and extensive limnological studies undertaken of these lakes until recently.[3]
The major ones are