Thursday, September 16, 2010

Glacial Armour Lets Mountains Rise High

Ripe for the buzz saw (Image: Egner Photography/iStock)

From New Scientist:

Glaciers limit mountain height by stripping rock off the top – but not always. If conditions are right, glacial ice will protect the rocks beneath to let mountains grow.

The upper reaches of high mountains are covered with snow all year round, allowing glaciers to form. As these rivers of ice move slowly downhill, they wear away the rocks beneath them, meaning that mountains should not grow much beyond the height of their snowline: any rock that is pushed up above this altitude will eventually get worn away by the ice. This is called the buzz-saw hypothesis, because, like superhuman circular saws, the glaciers effectively cut the heads off mountains above a certain height.

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