WHY are mountains only as high as they are? Part of the answer is that they are kept in check by a process known as the glacial buzz saw.
When glaciers form on a mountain, they carve amphitheatre-shaped hollows into them called cirques. Sara Gran Mitchell, a geologist at College of the Holy Cross in Massachusetts, and Elisabeth Humphries at the University of North Carolina at Chapel Hill measured the elevation of 14,000 cirques, now free of ice, around the world.
They found that mountain summits rarely rose more than 600 metres above the highest cirque. They also found that cirques, and peak heights, were higher near the equator and lower at the cooler high latitudes (Geology, doi.org/xpt). This suggests that cirques – and hence climate – play a crucial role in limiting the height of mountains.
Gran Mitchell says cirques may act as a "glacial linebacker" that takes mountains out at the knees. The glacier scours the floors of the cirque and eats away at the walls, steepening the slopes above and making them weak and prone to erosion.
This article appeared in print under the headline "Glaciers control a mountain's height"
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