October 12, 2011
Geologist Discovers Strange Boulders In Atacama
A geologist has discovered a geological process operating in a remote corner of northern Chile's Atacama Desert.
University of Arizona geologist Jay Quade was starting to feel sick when he asked his colleagues Peter Reiners and Kendra Murray to stop their truck.
Quade then noticed unusual half-ton to 8-ton boulders near the truck after stopping.
The unusually smooth boulders, Quade said, were the result of two million years of seismic waves.
The waves caused the boulders to gradually grind against the sandy plain to help smooth their sides.
This was just a hypothesis to Quade until another trip to Atacama led him to feel the power of a 5.3 magnitude earthquake underneath his feet while standing on a boulder.
"It was this tremendous sound, like the chattering of thousands of little hammers," Quade said in a press release. "The one I was on rolled like a top and bounced off another boulder. I was afraid I would fall off and get crushed."
He believes the boulders tumbled down from the hills above, most likely due to the earthquakes. The boulders then accumulate on the sand flat, only to be ground down by seismic waves.
"I was just astonished when this earthquake came along and showed us how it worked," Quade said in a press release.
Quade said the boulder top surfaces suggest they have been there for one to two million years and have experienced 50,000 to 100,000 hours of bumping and grinding.
Quade explained the phenomenon on Tuesday at the annual meeting of The Geological Society of America in Minneapolis.
Image Caption: Huge boulders in Chile's Atacama Desert appear to be rubbed very smooth about their midsections, leading University of Arizona geologist Jay Quade to wonder what could cause this in a place where water, Earth's most common agent of erosion, is as almost nonexistent. Photos courtesy Jay Quade.
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