NYT - Quelccaya Ice Cap Formation In Peruvian Andes That Took 1,600 Years To Form Melted In 25
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Of greater immediate interest, Dr. Thompson and his team have expanded on previous research involving long-dead plants emerging from the melting ice at the edge of Quelccaya, a huge, flat ice cap sitting on a volcanic plain 18,000 feet above sea level.
Several years ago, the team reported on plants that had been exposed near a meltwater lake. Chemical analysis showed them to be about 4,700 years old, proving that the ice cap had reached its smallest extent in nearly five millenniums.
In the new research, a thousand feet of additional melting has exposed plants that laboratory analysis shows to be about 6,300 years old. The simplest interpretation, Dr. Thompson said, is that ice that accumulated over approximately 1,600 years melted back in no more than 25 years.
If any time in the last 6,000 years these plants had been exposed for any five-year period, they would have decayed, Dr. Thompson said. That tells us the ice cap had to be there 6,000 years ago.
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http://www.nytimes.com/2013/04/05/world/americas/1600-years-of-ice-in-perus-andes-melted-in-25-years-scientists-say.html?_r=0