Previously Ignored Process For Breaking Down Rocks Important, UW Team Finds

Jan 26, 2021

A rock affected by weathering.
Credit George F. Mobley, National Geographic

There are two ways rocks break down. Chemical weathering happens when water dissolves minerals in a rock, causing cracks. Physical weathering happens as the surface erodes. Because there's less material on top of them, deep rocks rise towards the surface.

Cliff Riebe, a UW geology professor, and his team compared the different types of weathering. In the latter process, Riebe said there's less pressure, so the volumes of rocks expand and they crack.

"We measure the volumes and that gives us the physical component, and then we measure the geochemistry and that gives us the chemical component," he said. "Then we can look at both of them together and figure out what fraction is accounted for by physical versus chemical."

Riebe said most studies ignore physical weathering, but his team found that it's actually important, especially in dry climates like Wyoming.

"Understanding this weathering process can help us better predict it," he said. "Where is the weathering going to be most pronounced, what forest ecosystems are going to be most resilient during a drought."

Riebe says cracks from weathering hold water. More weathering means an ecosystem can store more water for dry periods.

Have a question about this story? Please contact the reporter, Ashley Piccone, at apiccone@uwyo.edu.