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This photo is from Photo Gallery: Arctic Climate Change
Alaska Permafrost Collapse
Photograph by Christine Dell'Amore
Thermokarst failures occur when permafrost—a layer of frozen soil in Earth's polar regions—thaws and becomes unstable, possibly releasing greenhouse gases into the atmosphere. Though the features occur naturally in some parts of the Arctic, many scientists suspect that rising temperatures are causing more to form. Until 2003, thermokarsts—such as this one, located about 155 miles (about 250 kilometers) north of the Arctic Circle—were unheard of in northern Alaska.