This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A University of Massachusetts Amherst-led research team has discovered that weaker rock in mountain landscapes erodes three times faster than harder rock—even on gentler slopes—and is one of the main attributes governing mountain erosion. The finding also challenges our current understanding of the relationship between erosion and the release of carbon dioxide, and suggests that geologists and atmospheric scientists may be underestimating the CO₂ contributions coming from the Earth's rocky places.
The research, recently published in Science Advances, depends on a new technique relying on common quartz grains, the rare isotope beryllium-10 (known as ¹⁰Be) and cosmic rays from exploded stars. Over the course of the universe's nearly 14 billion years, countless stars have exploded, and when they do, they blast out showers of cosmic shrapnel in the form of high-energy particles. These cosmic particles have been raining down on the Earth for uncountable ages at a constant rate.
When the particles penetrate rocks on the surface, ¹⁰Be is produced within quartz. For four decades, geologists have been able to harvest these quartz grains from rocks like granite and sandstone, in which the quartz grains are comparatively large, to test all sorts of hypotheses. But in rocks where the grains are too fine, such as shale, the conventional ¹⁰Be technique hasn't worked.
And that has limited geologists' abilities to accurately pinpoint things like erosion rates across a broad spectrum of rock types. That is, until Marder and his colleagues developed a new method for harvesting the rare isotope from such rocks. "When we look at landscapes, we are only seeing a snapshot in time," says Eyal Marder, a postdoctoral researcher in earth, geographic and climate sciences at the University of Massachusetts Amherst and the lead author of the new paper.
But researchers want to understand the full geological movie from start to finish in order to understand the land's life cycle. Marder and his team studied Colorado's East River Watershed, which drains approximately 465 square kilometers (180 square miles) of the southern Elk and West Elk mountains—jagged peaks whose most famous landmark, Crested Butte, is revered as one of the U.S.'s premier ski areas. The sheer alpine topography is notable for its diverse geological composition: a mix of incredibly durable igneous rock and much weaker shale, deposited by rivers eons ago.
Their new technique allowed Marder and his team to make a few surprising discoveries. As expected, weaker sedimentary rocks erode faster than harder igneous ones. What was surprising is how much faster they erode.
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