Permafrost

Permafrost is an often hidden element of Alaska’s geology. While it occurs underground, it shapes landforms on the surface. It is found in nearly 80% of Alaska and impacts how we build and maintain our physical infrastructure—roads, rail, pipelines, bridges, homes, commercial buildings, and factories. 

What is permafrost? It is ground that has been frozen for two or more years. The definition includes rock, soil, and ice with temperatures below 32°F (0°C).

The presence of permafrost in Alaska varies widely but can be broken up into 3 zones.  

• Along the Coastal Plain, which extends from the Brooks Range north to the Arctic Ocean, there is continuous permafrost.  This permafrost occurs just below the surface and extends to depths of 2000 feet! 

• Between the Brooks Range and the Alaska Range in interior Alaska, permafrost is widely present but not continuous.  It occurs further below the surface and reaches depths of less than 150 feet.  

• South of the Alaska Range, permafrost is largely absent, though there are isolated pockets. 

Permafrost is an important consideration for construction and engineering projects. Building on permafrost can cause it to melt, making the ground unstable. Ever wonder why much of the Alaska Pipeline is above ground?  That is to prevent the warm oil in the pipeline from melting the permafrost. If recent trends in warming average temperatures in Alaska continue, permafrost areas could destabilize and generate new challenges for Alaska’s maintenance and construction industries.