Wrangell Volcanic Field
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The Wrangell Volcanic Field is a
volcanic field A volcanic field is an area of Earth's Earth's crust, crust that is prone to localized volcano, volcanic activity. The type and number of volcanoes required to be called a "field" is not well-defined. Volcanic fields usually consist of clusters ...
stretching from eastern
Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...
in the
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
to the southwestern
Yukon Territory Yukon () is a territory of Canada, bordering British Columbia to the south, the Northwest Territories to the east, the Beaufort Sea to the north, and the U.S. state of Alaska to the west. It is Canada’s westernmost territory and the smallest ...
in
Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...
. The field includes the four highest volcanoes in the United States, Mount Bona, Mount Blackburn, Mount Sanford, and Mount Churchill, all of which exceed 15,000 ft (4,600 m) in elevation. It formed as a result of
subduction Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second p ...
of the Pacific Plate beneath the North American Plate at the easternmost end of the Aleutian Trench /sup>. The bulk of the Wrangell Volcanic Field lies within the
Wrangell Mountains The Wrangell Mountains are a high mountain range of eastern Alaska in the United States. Much of the range is included in Wrangell-Saint Elias National Park and Preserve. The Wrangell Mountains are almost entirely volcanic in origin, and they i ...
of Alaska, but the field also extends eastwards into the neighboring Saint Elias Mountains and the
Yukon Territory Yukon () is a territory of Canada, bordering British Columbia to the south, the Northwest Territories to the east, the Beaufort Sea to the north, and the U.S. state of Alaska to the west. It is Canada’s westernmost territory and the smallest ...
. 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 A shield volcano is a type of volcano named for its low profile, resembling a shield lying on the ground. It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more viscous lava ...
es,
stratovolcano A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with ...
es,
caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...
complexes, cinder cones, and extensive
lava flow Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...
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 in
glacier A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...
s and icefields, especially on the windward southern side of the ranges. The field is named for Mount Wrangell, a massive
shield volcano A shield volcano is a type of volcano named for its low profile, resembling a shield lying on the ground. It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more viscous lava ...
which has been active historically. The
stratovolcano A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with ...
of Mount 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 with
volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to r ...
(the White 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
Cenozoic The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...
subaerial
lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...
s and
pyroclastic rock Pyroclastic rocks are clastic rocks composed of rock fragments produced and ejected by explosive volcanic eruptions. The individual rock fragments are known as pyroclasts. Pyroclastic rocks are a type of volcaniclastic deposit, which are deposit ...
s. Over large areas extrusive rocks lie in flat undisturbed piles on a Cenozoic surface of moderate relief. Locally, however,
strata In geology and related fields, a stratum (: strata) is a layer of Rock (geology), rock or sediment characterized by certain Lithology, lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by v ...
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-Cenozoic baserocks along southwesterly dipping thrust faults. Considerable recent uplift, accompanied by rapid erosion, has reduced once vast areas of upper Cenozoic volcanic rocks to small isolated remnants. Although no centers younger than late
Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
are known in Canada, the eruption of
rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture (geology), texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained matri ...
pumice Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of extremely vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicula ...
, White River Ash, from Mount Churchill near the head of Klutlan Glacier blanketed large areas of northwestern Canada with
tephra Tephra is fragmental material produced by a Volcano, volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, ...
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 as Rabbit Mountain and Felsite Peak, which are now eroded to form an
outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth and other terrestrial planets. Features Outcrops do not cover the majority of the Earth's land surface because in most p ...
. Major volcanoes of the Wrangell Volcanic Field include: * Mount Bona, , Saint Elias Mountains * Mount Blackburn, , Wrangell Mountains * Mount Sanford, , Wrangell Mountains * Mount Churchill, , Saint Elias Mountains * Mount Wrangell, , Wrangell Mountains * Atna Peaks, , Wrangell Mountains * Regal Mountain, , Wrangell Mountains * Mount Jarvis, , Wrangell Mountains * Mount Drum, , Wrangell Mountains Volcanoes of the Canadian portion of the Wrangell Volcanic Field include: * Felsite Peak, , Coast Mountains * Rabbit Mountain, , Nutzotin Mountains


See also

* List of volcanoes in the United States of America *
List of volcanoes in Canada List of volcanoes in Canada is an incomplete list of volcanoes found in Geography of Canada, mainland Canada, in the Islands of Canada, Canadian islands and in Canadian waters. All but two Provinces of Canada, provinces, Prince Edward Island and ...
* List of volcanic fields * Volcanism in Canada


References

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External links


Alaska Volcano Observatory - Wrangell Volcanic FieldNational Resources Canada: Catalogue of Canadian volcanoes
{{Coord, 62.0272, -143.6217, display=title Volcanic fields of Alaska Volcanoes of Yukon Volcanic fields of Canada Landforms of Copper River Census Area, Alaska Potentially active volcanoes Polygenetic volcanic fields Landforms of Unorganized Borough, Alaska he:ראנגל-סנט אליאס#השדה הגעשי