Farouk El-Baz

Document Type

Article

Publication Date

1979

Abstract

Since the first detection of palcachannels beneath sand shects and sand duncs in the Sahara using Shuttle Imaging Radar (SIR-A) data, kcy advances in their understanding havc bcen made. The Sahara is curently the largest and driest region on Earth. However, it was drained by namerous rivers hat are now dry channels beneath sand sheets and sand dunes. The present Sahara rcflects pluvial conditions in the past, and the transitions from heavy rainfall to arid or hyper-arid conditions reveal major climate shifts. Here, we propose that the evolution of the Sahara was in response to stages of the location of the African Plate relative to the Earth Equator; i e., as a result of the northward drift of Africa in space and time. For instance, in the latc Eocene/Oligocene time, the Earth Equator was probably located at today's Chad and Sudan latiludes. This would have caused pluvial conditions throughout North Africa. With inereasing drift in space and time during Miocene, Pliocene, and Pleistocene time, the source points shifted. New valleys wcre formed and old ones were abandoned, and the length of the main stream of the Nile increased.

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