permafrost

Those who think history is by its nature a sort of settled permafrost will be surprised to see how the discipline has changed over the past half century.

These RNA sequences are the oldest ever recovered and come from mammoth tissue preserved in the Siberian permafrost for nearly 40,000 years.

The tundra had once been covered in a permanent layer of hard frozen soil, called permafrost.

Canada and Russia, where large amounts of ice and permafrost are melting, are losing the most fresh water.

"The thawing of permafrost at very high elevation led to the collapse of the summit," he explains.