Skip to comments.The Strange Rubbing Boulders of the Atacama
Posted on 10/11/2011 3:03:04 PM PDT by decimon
Boulder, CO, USA A geologist's sharp eyes and upset stomach has led to the discovery, and almost too-close encounter, with an otherworldly geological process operating in a remote corner of northern Chile's Atacama Desert.
The sour stomach belonged to University of Arizona geologist Jay Quade. It forced him and his colleagues Peter Reiners and Kendra Murray to stop their truck at a lifeless expanse of boulders which they had passed before without noticing anything unusual.
"I had just crawled underneath the truck to get out of the sun," Quade said. The others had hiked off to look around, as geologists tend to do. That's when Quade noticed something very unusual about the half-ton to 8-ton boulders near the truck: they appeared to be rubbed very smooth about their midsections. What could cause this in a place where Earth's most common agent of erosion water is as almost nonexistent?
About the only thing that came to mind was earthquakes, said Quade. Over the approximately two million years that these rocks have been sitting on their sandy plain perhaps they were jostled by seismic waves. They caused them gradually grind against each other and smooth their sides. It made sense, but Quade never thought hed be able to prove it.
Then, on another trip to the Atacama, Quade was standing on one of these boulders, pondering their histories when a 5.3 magnitude earthquake struck. The whole landscape started moving and the sound of the grinding of rocks was loud and clear.
(Excerpt) Read more at geosociety.org ...
That would be kind of cool to see in action.
I think I'll just take the guy's word for it. ;)
Remarkable. I wonder if the same thing can be found in CA with similar frequency of earthquakes?
Yes, the sides of the heads of California’s lunatic legislator-rockheads have all been worn smooth. However, there is little danger of any brains leaking out.
On the rocks ping.
Wind blown sand comes to mind. Note the ripples in the sand in the pics. His example pics also were mostly spaced apart rocks.
I remember when an earthquake hit my area a year or so ago. I didn’t feel any vibration, but heard a rumbling/roaring kind of sound which I knew had to be a quake (didn’t sound like anything else, for one thing), and it was. It was all the rocks rattling along their joint planes and other fractures.
Many people have gone out there, some even living out there for short spells. I don't think anyone has actually seen a rock move, but I could be wrong about that.
Mars seems to have them too.
“The Racetrack in Death Valley...”
My first thought as well.
Read a different theory couple months back that frost/condensation was enough to freeze around the rock at night and cause “expansion” in the soil up to about an inch into the soil hence moving the rock (very, very) a little at a time. Still doesn’t explain why one direction is usually observed however..
A zombie with a sense of humor.
Bump for reference. Interesting....
“the average boulder has experienced 50,000 to 100,000 hours of bumping and grinding while waiting for that nonexistent train.”
Well, at least they have something to keep them busy. Naughty boulders.
The condensation under a rock on the flat is influence by the direction the sun rises and the nearness of a land rise such as seen behind the rock in the picture. The condensation reduces the coefficient of friction of the rock on the flats soil and the weight of the rock effects the size of the ‘channel walls’, up to a point sustainable by the formation of cie crystals in the condensation enriched soil. ... The side-walls will be noticeable but never high no matter how large the bolder etching the channel.
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