News in Brief: Climate change carved canyons in Andes bit.ly/1a9CCXD - News in Brief: Climate change carved canyons in Andes Erosion came thanks to cooling and more rain, not tectonic activity By Erin Wayman Web edition: August 15, 2013 Erosion came thanks to cooling and more rain, not tectonic activity By Erin Wayman Web edition: August 15, 2013 Enlarge Carving Canyons Climate change that brought more rain to the northeastern Andean Plateau triggered the erosion that carved the area’s canyons (Peru’s Rio San Gaban canyon shown), geologists report. Credit: R. Lease The onset of a cooler climate 4 million years ago — rather than tectonics — helped carve deep canyons in the Andes, geologists report in the Aug. 16 Science. The researchers examined one of the many 1.5- to 2.5-kilometer-deep canyons that cut into the northeastern edge of the Andean Plateau in southern Peru. By dating when rocks at various depths within the chasm were exposed to the surface, the team determined that rapid erosion created the canyon. Geologists usually tie canyon formation to uplift triggered by tectonic activity in Earth’s crust or movement in the mantle. Once the surface rises, erosion usually starts right away, says coauthor Richard Lease, now at the U.S. Geological Survey in Anchorage, Alaska. But in this case, the region was in a tectonic lull when erosion began, Lease and colleague Todd Ehlers of Germany’s University of Tübingen say. Instead, they suggest, climate change activated canyon formation. Roughly 4 million years ago, cooling in the Pacific Ocean initiated periodic La Niña events that intensified storms in the region. Cooling in the North Atlantic would also have caused more rainfall, and thus more erosion. Citations R.O. Lease and T.A. Ehlers. Incision in the eastern Andean Plateau during Pliocene cooling. Science. Vol. 341, August 16, 2013, p. 774. doi:10.1126/science.1239132.[Go to] Suggested Reading A. Witze. Grand Canyon born by continental lift. Science News. Vol. 179, May 21, 2011, p. 12. [Go to] S. Perkins. A rapid rise for the Andes. Science News. Vol. 174, July 5, 2008, p. 11. [Go to] S. Perkins. Rodents tell a geologic tale. Science News. Vol. 170, November 11, 2006, p. 318. [Go to] A. Witze. Grand Canyon could be much older than thought. Science News. Vol. 183, January 12, 2013, p. 15. [Go to] - #science #sciencenews #sciencearticle #article
Posted on: Sat, 17 Aug 2013 02:08:19 +0000
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