Mountains grow faster than expected
6 February 2006
by Richard
Conan-Davies
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Mountain ranges rise to their height in as little as two million years according to two new studies from geologists at the University of Rochester. Carmala Garzione, one of the lead authors of the paper explained that "These results really change the paradigm of understanding of how mountain belts grow," Recently she was concentrating on the Bolivian Altiplano, which is a large, high elevation basin in the Andes Mountains in South America. Basically she looked at the amount of oxygen isotopes in rock strata in this basin. Oxygen has two isotopes 16 and 18. It is mostly 16 with a bit of 18. But as water vapour goes up into the atmosphere oxygen 18 is removed ( in fact it is a little heavier). So by measuring the amount of this isotope in rock layers can tell you how high the mountains were at particular times. She also used another technique that looked at temperatures of formation of carbonates and the kinds of isotopes of carbon. Since air temperature decreases with altitude, this a temperature-based recording of the rocks' original altitude should be preserved. At high temperatures individual atoms will vibrate more and their bonds break more easily. Because heavy isotope bonds are stronger, at lower temperatures and lower vibrational frequencies, the light isotope bonds are more likely to be broken. Her results suggest that Andes rose a kilometer per million years,. This means scientists can now assign a very specific--and very controversial--process to mountain uplift or formation. The theory is called "deBlobbing" The idea , roughly, is that as tectonic plates collide they buckle but there is a kind of blob underneath the plate that falls away and bobs up to push up the mountains faster |
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Original press release from University of Rochester
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