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Permafrost. Break the word down: Perma -- permanent or long-lasting

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and frost -- frozen. Permafrost is soil that has been frozen for at least

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two years. But typically, it’s been frozen for much longer, hundreds or even thousands of

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years. Permafrost is found in the Arctic, the Antarctic, and at high elevations.

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So, why do we care about a frozen layer of soil? Because the human-caused

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climate change that's warming Earth is warming the Arctic first and fastest. And as

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temperatures climb, permafrost thaws. Thawing permafrost is a problem

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for things people build. As frozen soil turns to mud and water, roads, runways,

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and buildings start to wobble and collapse.  And thawing permafrost packs a

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double punch by releasing planet-warming greenhouse gases. Over centuries,

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ancient plants and animals became frozen in the permafrost, which stored this material like a big

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freezer. When permafrost thaws, this organic material is eaten by microorganisms,

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releasing carbon dioxide and methane into the atmosphere, adding to the greenhouse

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gases released by human activities that thawed permafrost in the first place.