London: A University of Arizona-led research team has found that glaciers can help actively growing mountains become higher by protecting them from erosion.
The finding is contrary to the conventional view of glaciers as powerful agents of erosion that carve deep fjords and move massive amounts of sediment down mountains. Mountains grow when movements of the Earth`s crust push the rocks up.
The research is the first to show that the erosion effect of glaciers – what has been dubbed the "glacial buzzsaw" – reverses on mountains in colder climates.
The researchers were surprised, said first author Stuart N. Thomson, a research scientist in the UA department of geosciences. "We were expecting to see the buzzsaw."
The team discovered the protective effects of glaciers by studying the Andes Mountains in the southernmost region of South America, known as Patagonia.
UA co-author Peter W Reiners said, "It`s been thought that glaciers limit the height of mountain ranges worldwide."
The key is climate. Glaciers atop mountains in temperate latitudes flow downhill, scouring away the surface of the mountain. Over millennia, such erosion can reduce the height and width of a mountain range by miles.
However in very cold climates such as the Patagonian Andes, rather than scraping away the surface of the mountain, the team found that glaciers protect the mountain top and sides from erosion.
The team dubs the action of the cold-climate glaciers "glacial armoring."
"Climate, especially through glaciers, has a really big impact on how big mountains get," said Reiners, a UA professor of geosciences.
"What we`re seeing is that below certain latitudes, glacial buzzsaws clearly and efficiently operate, but south of about 45 degrees, it not only doesn`t work – it has the opposite effect. The glaciers actually protect the surface and allow the mountains to grow higher," he said.
The research is published in the September issue of journal Nature.