- Wrangell Volcanic Field
The Wrangell Volcanic Field is a
volcanic field stretching from easternAlaska in theUnited States to the southwesternYukon Territory inCanada . The field includes the four highest volcanoes in the United States,Mount Bona ,Mount Blackburn , Mount Sanford, andMount Churchill , all of which exceed 15,000 ft (4,600 m) in elevation. It formed as a result ofsubduction of thePacific Plate beneath theNorth American Plate at the easternmost end of theAleutian Trench .The bulk of the Wrangell Volcanic Field lies within the
Wrangell Mountains of Alaska, but the field also extends eastwards into the neighboringSaint Elias Mountains and theYukon Territory .The east-west length of the field is over 200 mile (320 km), while the width reaches up to 80 miles (130 km) in the central Wrangell Mountains. The field includes numerous
shield volcano es,stratovolcano es,caldera complexes,cinder cones , and extensivelava flow s, which have erupted throughout the past 26 million years. All of the higher peaks are less than 5 million years old, since the rate of glacial erosion is very high in this region of extreme snowfall and cold temperatures. Higher elevations of the field above 5,000 ft (1,500 m) are almost entirely covered inglacier s andicefield s, especially on the windward southern side of the ranges.The field is named for
Mount Wrangell , a massiveshield volcano which has been active historically. Thestratovolcano ofMount Churchill has had the largest recent eruptions, with two large-magnitude explosive eruptions in the last 2,000 years that blanketed most of the Yukon withvolcanic ash (theWhite River Ash ).The volcanoes of the western Wrangell Mountains are less than 5 million years old with the youngest lava flows are probably as young as 50,000 years ago. The Canadian portion of the field is dominated by scattered remnants of upper
Tertiary subaeriallava s andpyroclastic rock s. Over large areas extrusive rocks lie in flat undisturbed piles on a Tertiary surface of moderate relief. Locally, however,strata of the same age have been affected by a late pulse of tectonism, during which they were faulted, contorted into tight symmetrical folds, or overridden by pre-Tertary baserocks along southwesterly dipping thrust faults. Considerable recent uplift, accompanied by rapid erosion, has reduced once vast areas of upper Tertiary volcanic rocks to small isolated remnants. Although no centers younger than lateMiocene are known in Canada, the eruption ofrhyolite pumice ,White River Ash , fromMount Churchill near the head ofKlutlan Glacier blanketed large areas of northwestern Canada withtephra some 2,000 years ago.Most of volcanoes of the Western Wrangell Mountains are not like the other volcanoes located around the
Pacific Rim . Rather than erupting explosive lavas forming stratovolcanoes, they have been built by the buildup of hundreds of comparatively fluid lava flows to form shield volcanoes. Only the young Mount Wrangell still shows its shield-like form; the other, commonly older volcanoes have had much of their original form removed by glacial and other erosional processes, such asRabbit Mountain andFelsite Peak , which are now eroded to form anoutcrop .Major volcanoes of the Wrangell Volcanic Field include:
*Mount Bona , Convert|16421|ft|m|0|abbr=on, Saint Elias Mountains
*Mount Blackburn , Convert|16390|ft|m|0|abbr=on, Wrangell Mountains
*Mount Sanford, Convert|16237|ft|m|0|abbr=on, Wrangell Mountains
*Mount Churchill , Convert|15638|ft|m|0|abbr=on, Saint Elias Mountains
*Mount Wrangell , Convert|14163|ft|m|0|abbr=on, Wrangell Mountains
*Atna Peaks , Convert|13860|ft|m|0|abbr=on, Wrangell Mountains
*Regal Mountain , Convert|13845|ft|m|0|abbr=on, Wrangell Mountains
*Mount Jarvis , Convert|13421|ft|m|0|abbr=on, Wrangell Mountains
*Mount Drum , Convert|12010|ft|m|0|abbr=on, Wrangell MountainsVolcanoes of the Canadian portion of the Wrangell Volcanic Field include:
*Felsite Peak , Convert|8301|ft|m|0|abbr=on, Coast Mountains
*Rabbit Mountain , Convert|6857|ft|m|0|abbr=on, Nutzotin MountainsReferences
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ee also
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List of volcanoes in the United States of America
*List of volcanoes in Canada
*Volcanoes of Canada External links
* [http://www.avo.alaska.edu/volcanoes/wrangells.php Alaska Volcano Observatory - Wrangell Volcanic Field]
* [http://gsc.nrcan.gc.ca/volcanoes/cat/belt_wrangell_e.php National Resources Canada: Catalogue of Canadian volcanoes]
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