Explainer: Ice sheets and glaciers

Here’s how and where these ice blankets form

By Douglas Fox, 16:39 PM September 4, 2013


Most of Antarctica’s ice sheet is made up of slow-moving ice. This ice generally moves no more than a few meters, or tens of meters per year. But in some places there are corridors of ice that flow much more quickly. These rivers of ice, called ice streams, or glaciers, often flow hundreds of meters per year. In this map, the Antarctic Ice Sheet is color-coded according to how quickly the ice flows. The fast-flowing ice streams appear in blue or purple. Credit: Eric Rignot, NASA/JPL/UCI



Ice covers nearly all of Antarctica’s 14 million square kilometers (5.4 million square miles) of land. In some places, that ice is nearly 4 kilometers (2.5 miles) thick. It formed as snow piled up over many thousands of years. Gradually, the snow compacted into ice. Scientists call this vast, frozen blanket an ice sheet. A second, smaller ice sheet covers much of Greenland.


An ice sheet may look stationary, but it is always moving.


The lower layers are under crushing weight — in some place...

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