60秒科学:冰能给山拔高,你相信吗?（在线收听）

Moving glaciers can cause erosion on mountains, but the coldest glaciers, frozen in place, protect mountains and allow them to grow taller. Cynthia Graber reports

冰川移动会侵蚀山地（冰川移动通常会导致出现角峰和冰斗谷），但是最冷的冰川被冻得固定在某个地方，就会保护山脉并且还会让它们“长高”。Cynthia Graber 报道

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.