Monday, August 1, 2011

The first true view of global erosion

Joshua E. Brown in the University of Vermont News talks about a cool method for measuring erosion. I always knew that someone would find a use for beryllium-10!: ...For more than a century, scientists have looked for ways to measure and compare erosion rates across differing landscapes around the globe—but with limited success. “Knowing the background rate of erosion for a place is extremely important,” says University of Vermont geologist Paul Bierman, “if you want to compare it to what’s coming off the landscape today because of human impacts like agriculture, development, and forestry.”

Since the mid-1980’s, measurements of a rare radioactive element—beryllium-10 that appears in quartz bombarded by cosmic rays in the top few feet of Earth’s surface—have greatly improved geologists’ ability to estimate erosion rates. But these experiments have been done on a local or regional scale, using a variety of methods, calculation constants, and corrections. Comparisons between climate zones and differing rock types have been difficult—cutting off a global perspective.

Now Bierman and his graduate student, Eric Portenga, have taken twenty years worth of this disparate data, compiled 1599 measurements from eighty-seven sites around the world, and recalculated it with a single, up-to-date method. Their work, “provides the first broad, standardized view of pre-human, geologic erosion rates,” they write in “Understanding Earth’s eroding surface with 10Be,” published in the August edition of GSA Today, an open-access journal, available online July 26, 2011.

...The method used in this new study can provide a good tool for measuring the sustainability of modern agricultural practices, Bierman notes, since the beryllium-10 data shows the rate at which landscapes have been changing in the recent geologic past: the last thousand to several-hundred-thousand years. “If human impacts result in rates faster than we measure, it’s non-sustainable,” he says.

...“Following this study, we can start to answer big questions like, ‘how does climate drive erosion?’” says Bierman. In other words, a clearer picture of what global erosion has looked like in the recent past will start to illuminate what is likely to happen in the future as human impacts and land-use decisions play out...

The Delicate Arch in Arches National Park, Utah, National Park Service

No comments: