最冷冰川能保护大山

Glaciers slowly grind their way over mountains and plains, moving immense boulders and carving out fjords. That’s true in temperate regions, where glaciers – glacially – flow downhill. Over thousands of years, the frozen masses can scrape miles off of mountains. Researchers call it the glacial buzz-saw.

But for the very coldest climes, researchers now offer a counter-intuitive view of glaciers – they actually help mountains grow. The finding was published in the journal Nature.

A team led by scientists from the University of Arizona studied mountains in remote areas of Patagonia in South America.The Andes are actively growing. Hot rocks are shoved to the top, and erosion brings them back down the sides.The team collected 146 samples of rocks from mountainsides and then dated the rocks’ so-called cooling age, which reveals when the rock was exposed by erosion.

They found that erosion happened faster in the warmer mountains to the north, and more slowly in the colder mountains in the south. Turns out that when glaciers are cold enough they don’t move much. Instead, they seal the mountains, protecting them from erosion. The scientists call the effect ‘glacial-armoring’: an invaluable assist for peak performance.

—Cynthia Graber