The world's largest hot desert (seeing as technically Antarctica is the largest desert, though cold), the Sahara measures in at over 9 million square kilometers, and covers the majority of northern Africa. With an intermittent history that some believe may go back as far as 3 million years, recent research questions how it made its transition from lush greenery to hot sandy desert.
According to the European-US-Canadian team of scientists behind the study, the Sahara finished a slow transition 2,700 years ago to become the desert that we know today. This is in direct contrast to previously held thoughts that the desertification of the Sahara came abruptly.
Six thousand years ago we know that the massive northern area of Africa was very green; an area filled with trees, savannas and lakes.
Sadly, most of the physical elements from that period of time though have been lost, and thus for a long time the exact tale of the Sahara's geographic evolution has too been lost. However the scientists looked at layers of sediment in one of the largest remaining Saharan lakes, Yoa, located in Chad. This sediment managed to take them back through six millennia of climate history for the region.
Their findings – upon conducting soil tests and reviewing biological indicators in the sediment – contradict previous modeling that showed a rapid collapse of vegetation in the region some 5,500 years ago. This according to Stefan Kropelin, a geologist at the Prehistoric Archaeology Institute of the University of Cologne who took part in the new study.
Peter de Menocal of Columbia University published a study in 2000, where he reviewed sediments in the west of Mauritania, and found a sudden increase in wind-carried dust blown off the Sahara region, suggesting what he believed to be a swift climate change. However Kropelin believes that the data was misinterpreted.
Posted by Josh Hill. Image credit: Jeff Malon.
Source link:
http://www.physorg.com/news129617309.html
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