Mush of Alaska is covered with permafrost, a layer of permanently frozen soil that lies just below the surface. Warmer temperatures are now causing the permafrost to melt in some places. As it melts, the ground softens and water wells up to the surface. Trees growing in the top soil layer tip sideways and their roots drown. Melting permafrost is creating big problems for Alaskans. Where houses were build one once-solid frozen ground, foundations are shifting and cracking. Roads are buckling and sinking. Even the Trans-Alaska Pipeline, which carries petroleum 800 miles from Alaska’s North Slope fields to the port for shipping.

Melting permafrost is also increasing the risk of erosion and landslides. Alaska’s more than 2,000 glaciers are causing worries, too. Scientists have expected the glaciers to get thinner as a result of warmer temperatures. But in 2002 studies showed than many Alaska’s glaciers are shrinking even faster that scientists had thought.