ABSTRACT
Alaska comprises approximately 20% of the geographic area of the United States; the geologic history of the region, ranging from its tectonic history to its volcanic history is complex. The Alexander Terrane encompasses much of eastern and particularly southeastern Alaska, and illustrates the assembly of the southern margin of this part of North America. The geology of southern Alaska is dominated by two major collisional events, the arrival of the Wrangellia composite terrane in the Cretaceous and the arrival of the Yakutat terrane in the Cenozoic. Within the Wrangellia composite terrane is a thick rock unit called the Matanuska Formation, a largely marine rock unit that captures some of the history of collision of Wrangellia with the rest of Alaska. The North Slope of Alaska is that part of the state defined as the land that slopes north from the Brooks Range to the Arctic Ocean. It comprises three physiographic provinces: mountains, Arctic Foothills, and Arctic Coastal Plain.
