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Oceanic plates in the Pacific Ocean subducted in trenches offshore, carrying volatiles such as water and carbon dioxide with them, leading to rock melting and volcanic activity. Intense volcanism built up Alaska's mountains until a slowing of eruptions in the late Cretaceous around 80 million years ago.
The subduction along the trench gives rise to the Aleutian Arc, a volcanic island arc, where it runs through the open sea west of the Alaska Peninsula. As a convergent plate boundary, the trench forms part of the boundary between two tectonic plates. Here, the Pacific plate is being subducted under the North American plate at a dip angle of ...
Here, the Pacific Plate is being subducted underneath the North American Plate and the rate of subduction changes from west to east from 7.5 to 5.1 cm (3.0 to 2.0 in) per year. [2] The Aleutian subduction zone includes two prominent features, the Aleutian Arc and the Aleutian Trench. The Aleutian Arc was created via volcanic eruptions from ...
Tectonic map of Alaska and northwestern Canada showing main faults and historic earthquakes Denali Fault and the Denali National Park boundary. The Denali Fault is a major intracontinental dextral (right lateral) strike-slip fault in western North America, extending from northwestern British Columbia, Canada to the central region of the U.S. state of Alaska.
The rapid conversion and the gentle subduction angle of the Pacific plate under the North American plate also caused a back-arc region of tectonic deformation that spans 700 km from the Aleutian Arc into the interior of Alaska to form. [5] These conditions have allowed for a multitude of major earthquakes to be measured throughout Alaska's history.
Tectonic map of Alaska and northwestern Canada showing main faults and historic earthquakes. The Queen Charlotte triple junction is a geologic triple junction where three tectonic plates meet: the Pacific plate, the North American plate, and the Explorer plate.
The segment of the Aleutian Volcanic Arc from the central Aleutian Islands to the western Alaska Peninsula, which includes Aniakchak, features some of the largest volcanoes of the arc; [44] the formation of the Aniakchak caldera may be facilitated by a tectonic discontinuity that allows magma to accumulate in the crust. [45]
The southern part of Alaska is composed of a series of terranes that have been pushed against the North American landmass by the action of plate tectonics. The Pacific Plate moves northwestward relative to the North American Plate at about 2 inches (5.1 cm) to 2.5 inches (6.4 cm) per year, [29] meeting the continental landmass in the Gulf of ...