permafrost

American  

[pur-muh-frawst, -frost] / ˈpɜr məˌfrɔst, -ˌfrɒst /

noun

1. (in Arctic or subarctic regions) perennially frozen subsoil.

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permafrost British  

/ ˈpɜːməˌfrɒst /

noun

1. ground that is permanently frozen, often to great depths, the surface sometimes thawing in the summer

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permafrost Scientific  

/ pûr′mə-frôst′ /

1. A layer of soil or bedrock that has been continuously frozen for at least two years and as long as tens of thousands of years. Permafrost can reach depths of up to 1,524 m (4,999 ft). It is found throughout most of the polar regions and underlies about one fifth of the Earth's land surface.

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Etymology

Origin of permafrost

First recorded in 1943; perma(nent) + frost

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Explanation

Permafrost is ground that is frozen permanently. As you can imagine, permafrost is extremely cold. If you know that frost has many cold-related meanings and permanent means "always," then you should be able to figure out what permafrost is: ground that is permanently frozen. You won't be able to plant a garden in permafrost — or do much with it — since it’s so hard and cold. You won't find permafrost in warm climates or places that have distinct seasons. Permafrost only exists in areas where it's cold all the time, so the ground never thaws out.

Example Sentences

See Examples For:

permafrost

The major destruction of hydropower infrastructure underscored the risks of that strategy in a region where glaciers are retreating, permafrost is thawing and extreme hazards are becoming harder to predict.

From Barron's ● Sep. 27, 2026

The World Weather Attribution study, published on Thursday, said the disaster was the result of a "compound event" caused by rising temperatures, thinning glaciers, thawing permafrost and pre-existing geological weaknesses.

From BBC ● Sep. 17, 2026

At the same time, increasing permafrost thaw is further weakening Arctic coastlines, making them more susceptible to erosion and storm damage.

From Science Daily ● Sep. 14, 2026

Vanishing ice and permafrost make glaciers more prone to snapping and the underlying bedrock more likely to fracture.

From The Wall Street Journal ● Sep. 9, 2026

How could the permafrost have given way like that?

From "Two Degrees" by Alan Gratz

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