Climate May Grind Mountains into the Dirt with Moving Glaciers
For the first time ever, researchers have attempted to measure all of the material leaving and entering a mountain range over millions of years. They found that glacial erosion can actually wear down a mountain faster than plate tectonics can build it.
In this latest study, the researchers mapped a huge submarine sediment fan in the Gulf of Alaska built by sediment eroded from the nearby mountains. Next, the scientists recovered sediment cores to understand the fan environments and recent history.
"It turns out that most sediments were younger than we anticipated, implying that erosion was higher than we expected," said Sean Gulick, one of the researchers, in a news release. "About a million years ago, short 40,000-year climate oscillations jumped into a new mode with stronger, 100,000-year long glacial cycles, and erosion of the mountains accelerated under attack from ice. In fact, more rock was eroded than tectonics has replaced."
Mountain ranges form when tectonic plates thrust into one another over millions of years and scrunch up the Earth's outer crust. As these mountains are built, though, other agents wear them down. In this case, the researchers found that climatic processes can drive glaciers to outstrip mountain building over a span of a million years.
"People often see mountain ranges as permanent, but they aren't really," said John Jaeger, co-chief scientist, in a news release. "If more rock is pushed in, they grow, and if more rock is eroded away, they shrink."
The findings are published in the journal Proceedings of the National Academy of Sciences.
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