University of Alaska Fairbanks    |    Scenarios Network for Alaska + Arctic Planning


This map shows detailed geological units for the state of Alaska.

No legend is shown due to the large quantity of different geological units present on the map.

Choose a location below by community name, coordinates, or by clicking on the map to select a point.

  • ✓  Detailed Geological Units

In Paleozoic and early Mesozoic times (541 to 250 million years ago), much of what is now continental Alaska were ocean basins. These ocean basins were later squeezed and uplifted in response to tectonic plate movement.

Mid-late Mesozoic was the time of the most dramatic changes in Alaska geography and many of the motions initiated then persist today. Widespread intrusion of granitic bodies into existing rocks also occurred during the Mesozoic, presumably also a result of the dynamics of lithospheric plate collision.

During the early Tertiary period (60 to 30 million years ago) extensive volcanic activity occurred, particularly in the Wrangell Mountains, the Alaska Peninsula, and the Aleutian Islands. During this warm period, large peat swamps formed and subsequently produced the coal deposits in the Cook Inlet region and on the northern side of the Alaska Range. Throughout the late Tertiary (30 to 2 million years ago) volcanic activity remained widespread.

During the Pleistocene ice age (2.5 million to 12 thousand years ago), broad snowfields formed in the Brooks, Alaska, and Coast Ranges and filled the trough between the Alaska Range and the coast ranges. Great glaciers from the snowfields carved the mountains and valleys of Alaska into their present shape and provided the sediments that now cover valley floors and basins.