Glacial erosion, plate tectonics, mountain responses
— Photo: AP
Unexpected: Intense glacial erosion can effect mountain growth.
Intense glacial erosion has not only carved the surface of the highest coastal mountain range on earth, St. Elias range in Alaska, but has elicited a structural response from deep within the mountain.
This interpretation is based on real-world data now being reported, which supports decades of model simulations of mountain formation and evolution regarding the impact of climate on the distribution of deformation associated with plate tectonics.
A team of researchers from seven universities report the results of their field studies, on the structural response of the St. Elias range to glacial erosion, in Nature Geosciences. The St. Elias range is a result of 10 million years of the North American plate pushing material up as it overrides the Pacific plate, then the material being worn down by glaciers. A dramatic cooling across the earth about three million years ago resulted in the onset of widespread glaciation. A million years ago, glacial conditions became more intense and glaciers grew larger over longer periods, and transitioned into more erosive ice streams that changed the shape and evolution of the mountains.
The process continues today, resulting in the particularly active and dramatic St. Elias ‘orogen’ – geologists’ word for mountains that grow from collision of plates.
Models create a simplified numeric version of an orogen. Then scientists can change variables in the mathematical formula to determine what happens as a result of climate. “Models are important in that they showed us that climate change can effect mountain growth,” Spotila said. “And the St. Elias orogen behaves very differently than ones that are at lower latitudes and receive most of their precipitation as rain,” he said. — Our Bureau
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