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Regional Geology of North America

Alaska Physiographic Provinces

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Alaska encompasses an expansive region of the Western Cordillera (Figure 292). Belts of mountain range border both sides of a central lowlands and plateaus region. The southeastern Alaska Panhandle consists of an archipelago of islands and coast ranges. The mountainous coastline bordering the Gulf of Alaska has glaciers and fjords (submerged glaciated valleys). Cool climates and high precipitation are responsible for numerous ice caps and alpine glaciers. Some of the glaciers reach the ocean, forming tidewater glaciers, such as at Glacier Bay National Park and Kenai Fjords National Park (Figure 293 and 294).

The Pacific Plate is colliding directly with the North American Plate. The results include the highest mountain ranges and most active volcanoes on the continental United States. Denali National Park hosts the highest peak in North America (Figure 295). Wrangell-St. Elias National Park and Preserve encompasses a large region extending from the coast into the Alaska Range and is host to the Wrangell Volcanic Field (Figure 296). The Aleutian Range is volcanic arc that extends from near Anchorage to the Aleutian Island Chain which extends about 1,200 mile westward from the Alaska Peninsula toward the Kamchatka Peninsula in Russia and divides the Pacific Ocean from the Bering Sea. The interior of Alaska is a series of low mountain ranges, plateaus and lowlands drained by the Yukon River. The northern Alaskan Brooks Range is a more ancient mountain range that is bonded on the north by the" North Slope" Arctic Coastal Plain and continental margin basin that is host to Alaska's major oil fields.
Map of physiographic features in Alaska.
Fig. 292. Map of physiographic features in Alaska. The Aleutian Trench runs along the Pacific margin of Alaska and Aleutian Islands and is an active convergent plate boundary.
Satellite view of tidewater glaciers in Glacier Bay National Park. Kenai Fjords National Park is on the Gulf of Alaska near Seward, Alaska. Denali, Mt. Drum,
Fig. 293. Satellite view ice-capped mountains and tidewater glaciers in Glacier Bay National Park. Fig. 294. Kenai Fjords National Park has glaciers and submerged valleys along the Gulf of Alaska near Seward, Alaska. Fig. 295. Denali, elevation, 20,301 feet, is the highest mountain in North America—in Denali National Park. Fig. 296. Mt. Drum is a Pleistocene volcano in Wrangell-St. Elias National Park and Preserve, Alaska.
http://gotbooks.miracosta.edu/geology/regions/alaska.html     1/20/2017
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