Permafrost

Permafrost is ground that has been frozen for at least two years straight. It is found in very cold regions near the Arctic and on high mountains. Some permafrost has been frozen for thousands of years. It covers about a quarter of all the land in the Northern Hemisphere.

What Is Inside Permafrost

Permafrost is a mixture of frozen soil, rock, and ice. Some permafrost contains ancient plants, animals, and even woolly mammoths perfectly preserved by the cold. The frozen ground can be hundreds of feet deep. Only the very top layer, called the active layer, thaws in summer.

Melting Permafrost

As Earth's climate warms, permafrost is starting to melt. This is a big concern for scientists. Melting permafrost releases greenhouse gases that were trapped in the frozen ground. Buildings and roads built on permafrost can crack and collapse as the ground softens.

Fun Facts

• Permafrost covers about 25 percent of the land in the Northern Hemisphere.
• Some permafrost in Siberia has been frozen for over 700,000 years.
• Perfectly preserved woolly mammoths have been found frozen in permafrost.

Did You Know?

The world's permafrost contains about twice as much carbon as the entire atmosphere! If it all melted, it could release huge amounts of greenhouse gases.