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Rain really does move mountains, study finds

Oct. 16 (UPI) — Scientists have finally shown that precipitation and erosion rates influence the movement of mountains. Researchers detailed the breakthrough in a new paper, published Friday in the journal Science Advances.

The role that rain — and climate — plays in the evolution of mountain changes has been debated for decades. It seems intuitive that rain erodes mountains, altering a range’s topography, and even its tectonics, but the link has been difficult to prove.

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“Previously, many papers have brought together large datasets and found relationships ranging from a strong correlation to no correlation between rainfall and erosion rate,” Byron Adams told UPI in an email.

“The problem with the studies that suggested there was a strong correlation was that they did not provide a physical mechanism for why rainfall would affect erosion,” said Adams, earth scientist and research fellow at the University of Bristol.

To establish a connection between climate patterns and erosion rates, researchers precisely dated and mapped quartz sand grains across the slopes of the central and eastern Himalaya in Bhutan and Nepal.

Researchers used a novel dating technique that relied on the precise measurement of a rare element, Berllyium-10, in quartz samples.

“Berllyium-10 is produced within quartz when cosmic radiation, mostly neutrons, from outer space travels through the atmosphere and strikes the nucleus of an Oxygen-16 or Silicon-28 atom in the mineral,” Adams said. “When this interaction occurs, the atom breaks apart, or spalls, and new elements are formed including Berllyium-10.”

Berllyium-10, or Be10, is a very rare form of Berllyium, so scientists can be confident that its presence in quartz is a measure of what’s called “cosmogenic spallation.”

“Because we know the flux of cosmic radiation and the production rate of 10Be in quartz, we can use this technique to keep track of time,” Adams said.

In other words, by counting Be10 atoms, scientists can measure how long quartz sands have been exposed to the heavens in any given place on mountain sides and in river valleys.

“To make our erosion rate measurements we need to extract very small amount of Berllyium-10 from river sands and measure it very precisely with mass spectrometers,” Adams told UPI.

For the study, researchers combined their precise erosion rate measurements with precipitation and elevation data, and then used sophisticated numerical models to make sense of it all.

The analysis allowed the research team to isolate the influence of rainfall on erosion rates. The breakthrough helped researchers improve the accuracy of simulations for mountain tectonics.

“We found that if we used our new understanding of how the rivers are responding to rainfall, we could more accurately constrain the geometry and velocity of the active faults in Bhutan,” Adams said.

While researchers were able to confirm the influence of precipitation on erosion and local tectonic activity in the Himalayas, Adams suggests there is more work to be done to understand the true scope of this phenomena.

“The question that remains is: Is this a big enough change to drive crustal flow?” he said.

Researchers are currently working to expand their analysis across the entirety of the Himalayas and to use their findings to update risk models for landslides, dam breaches and fault slips.

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Science News – UPI.com

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