Alaska: Tectonics and Earthquakes

8min 40s Novice

How do tectonics change across the 4,000-km-long trench?

Alaskan tectonics are dominated by the Pacific-North American plates. The megathrust boundary between the plates results in both the 4,000-km-long Aleutian Trench and in the arc of active volcanoes that lie subparallel to the trench. This animation discusses the range of tectonic activity from megathrust earthquakes to accretion of geologic terranes.

Alaskan tectonics are dominated by Pacific-North American plate interaction. The megathrust boundary between the plates results in both the 4,000-km-long Aleutian Trench and in the arc of active volcanoes that lie subparallel to the trench. This animation discusses the range of tectonic activity from megathrust earthquakes to accretion of geologic terranes. Along the trench, the rate of convergence ranges from 5 cm/year on the east to 7.8 cm/year on the west. The angle of subduction also changes from shallow in the east to steep in the west. In the Gulf of Alaska region, the subduction of the Yakutat plateau complicates the area, and is responsible for mountain building in the Chugach-St. Elias Ranges and the Alaska Range.

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Keypoints:

Alaskan tectonics includes:

  • Subduction of the Pacific Plate yields large earthquakes & volcanoes
  • Changing angle of subduction affects the overlying position of volcanoes
  • Subduction of an older thicker Yakutat Plateau atop the Pacific Plate puts more compressive pressure on the overlying continental plate causing greater mountain building

 

 

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