Permafrost, despite its name, is not always frozen. Soil composition, the presence of salt and other factors can keep some of the ground from actually freezing, even as the temperature remains below the freezing point.

Across much of Alaska, Canada, Russia and Antarctica the ground is in fact frozen year round, however to depths of as much as 5000 feet. A relatively thin active layer near the top may be subject to a yearly freeze-thaw cycle. Allowing ground vegetation to survive.

As the planet warms, the effect of a meltdown in permafrost areas is a subject of debate. Some have speculated for example , that a widespread thaw would release massive amounts of greenhouse gases now trapped in the permafrost into the atmosphere, further warming the planet. 

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