April 23, 2017
Each Sunday we present a notable item from our archives. This EPOD was originally published April 22, 2003.
The photo above shows a classic example of exfoliation. The U-shaped Coquihalla valley in British Columbia, Canada was carved by glaciers tens of thousands of years ago. As the overlying glacial material was removed, the rocks that had formed underneath the massive ice sheet rose up (isostasy) and tried to expand. Isostasy is also known as glacial rebound. Rocks, of course, aren’t very flexible so instead of expanding, their outer layers are peeling off like onion skins -- the process of exfoliation.
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