Instead of wearing mountains down, evidence from Europe's high Alps shows that glaciers shield summits from erosion, acting as a protective lid. French scientists studied erosion on Mont Blanc, western Europe's highest peak, below and around its glaciers.
Cold ice at the highest points froze to the mountain rock and played little part in erosion, the team said. In contrast, water and rain eroded glacier-free areas 10 times faster than areas protected by the glacier.
The research was part of Cécile Godon's doctoral research at Université de Savoie, located on the edge of the French Alps, and appeared in the journal Earth and Planetary Sciences Letters. The study focused on the Bossons glacier, which flows down the northern face of Mont Blanc towards the French town of Chamonix.
Rock debris, carved from the mountain at the toe of the Bossons glacier and sediments washed out in high mountain streams were compared with erosion in nearby glacier-free areas. The researchers found that the cold glacial ice protected the mountain from erosion, rather than promoting it.
These results may explain the high altitude of the Alps. Driven by the tectonic collision of Europe with Africa, the high alpine bedrock is rising about one millimetre each year. Glacier-free areas of the Alps erode at a similar rate but where the mountains are protected by ice, the peaks wear away at one tenth that rate.