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Ancient Lakes Responsible For India's Historic Floods?

A Northwest researcher has uncovered remains of ancient ice-dammed lakes near Lhasa, Tibet that may have given rise to the flooding events recounted in the oral history of Tibet and India. 

Working along the Tsangpo River with a team sponsored by the National Science Foundation, geomorphologist David R. Montgomery has located lake sediments of silt and clay halfway up the steep valley walls of the Tsangpo River bed. These embedded sediments may be the key to unlocking a world now long forgotten.

With the elevation of the Tsangpo River already at 10,000 ft above sea level, and surrounding glacier peaks towering at 14,000 ft, the discovery of quiet-water sediments was unexpected in this kind of terrain.

Montgomery sought to explain the lakes' existence. "You have essentially a glacier bulldozer that shoved all this dirt and filled in a huge valley, damming the river with ice, backing it up and creating these huge lakes," says Montgomery, a University of Washington professor of earth and space sciences. The results of evidence of megafloods down the Tsangpo River were published in a recent edition of Quaternary Research.

The existence of two massive ancient lakes, dating from 10,000 and 1,200 years ago, is further supported by evidence of monsoons whose increased moisture allowed snow to accumulate upon the Himalayas, providing a constant source of ice to dam these lakes. As the ice began to melt, the unstable dam would have given way, causing severe flooding and producing enough force to wipe out an unpresuming city below.

While evidence points to two lakes of specific time periods, it is possible that this process of damming and draining the lakes occurred numerous times throughout history. Examining the effects of burst flooding could shed light on historical lost civilizations. These floods flowed into India, and that's where scientists need to look for clues, says Montgomery. "It could be like looking for a needle in a haystack, there's no guarantee you'll find it,” he cautions, but considering the force generated by over 850 cubic kilometers of water rushing down a narrow gorge, the possibility for further discovery is waiting downstream.

Jessica Cromheecke is an undergraduate studying biochemistry and economics at the University of Washington.

Images

Top: Ancient lake may have once filled the valley of Tsangpo River in Tibet.


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