The results of the research, carried out on the Patagonian Andes, came as a surprise. In previous studies, glaciers have been shown to act as powerful agents of erosion, carving out deep valleys as they move slowly down the mountainsides – an effect dubbed the ‘glacial buzzsaw’. As movements in the Earth’s crust push mountains higher, the glacial buzzsaw grinds them back down, limiting their growth.

Mountain growth pushes hot rocks from deep in the Earth’s crust upwards. As erosion removes surface material from the mountains, these rocks get closer to the surface. The speed at which they cool gives an indication of how rapidly surface material above them is being removed by erosion.

The researchers collected soccer-ball-sized rocks from the base of glaciers on mountains along the Andes, from 38°S to 56°S. They then used independent dating methods to calculate the rates at which the rocks cooled. They found that rocks from the north had cooled more rapidly than those from the south, indicating that erosion was slower in the south.

‘What corroborates this is that the mountains are higher in the south than in the north. Uplift is winning in the south, and the glacial buzzsaw is winning in the north,’ said one of the study’s authors, Peter Reiners.

The team argues that in the colder southern areas, glaciers are protecting the mountains from erosion, allowing them to grow higher.

November 2010