New findings of climatologists published in Nature reveal that the formation of the Sahara desert may have started up to 7 million years ago, more than twice as long ago as previously thought. Following the discovery of aeolian dune deposits that challenged the widely accepted age of approximately 2 – 3 million years for the Sahara desert, the scientists have used climate models to simulate the mechanisms behind the onset of aridification in northern Africa. Their results show that the origination of the Sahara desert may be related to shrinking of the Tethys Sea and the uplift of the Arabian Peninsula, associated with the northward movement of the African tectonic plate towards the Eurasian tectonic plate during the late Miocene. This reorganization of landmasses is thought to have significantly weakened the African summer monsoon, resulting in a reduced flow of moisture from the Atlantic Ocean and increasingly arid conditions in northern Africa. Until now, it was long believed that the desertification of northern Africa was related to the onset of glaciation on the Northern Hemisphere during the Pliocene and Pleistocene.
Journal reference: Zhang, Z., Ramstein, G., Schuster, M., Li, C., Contoux, C., & Yan, Q. (2014). Aridification of the Sahara desert caused by Tethys Sea shrinkage during the Late Miocene. Nature, 513(7518), 401-404.
Image: Sand dunes of the Sahara desert at sunset in Fezzan, Libya. Source: Luca Galuzzi, Wikimedia Commons.