Amak Volcano

Amak Volcano

Amak Island and volcano at top
Highest point
Elevation 1,601 ft (488 m)
Coordinates 55°25′02″N 163°08′49″W / 55.41728°N 163.14687°W / 55.41728; -163.14687Coordinates: 55°25′02″N 163°08′49″W / 55.41728°N 163.14687°W / 55.41728; -163.14687
Geography
Amak Volcano

North Pacific, part of Alaska

Parent range Aleutian Islands
Geology
Mountain type Stratovolcano
Volcanic arc Aleutian Arc
Last eruption 1796

Amak Volcano is a basaltic andesite stratovolcano in the Aleutian Islands of Alaska, USA, 618 miles (995 km) from Anchorage.[1] It is located on the eponymous island, 31 miles (50 km) from Frosty Volcano and near the edge of the Alaskan Peninsula's western flank. Only boats are allowed to access the island with a certain permit.

Blocky (dotted with flat blocks of minerals and crystals) lava flows[2] stream from its summit to its flanks. Three historical eruptions have taken place – two within the 18th century, the first from 1700–1710, and the latter in 1796. The earliest prehistoric eruption was believed to have taken place between 3050 and 2050 BCE.

Accessibility

Cold Bay, the city nearest Amak, is easily accessible by plane. Amak is accessible only by boat; airplanes are not permitted to land on the island. Private boat rides to Amak are available in Cold Bay, but for access to the Aleutian Islands, a permit is required from the United States Fish and Wildlife Service.[3]

Geography and geology

Amak Island lies in the Bering Sea, north of the main archipelago of the Aleutians. It is one of two islands (along with Bogoslof Island) that are 31 miles (50 km) north[4] of the main range.[3]

The United States has the most active volcanoes in the world, many of them geologically young.[5] In Alaska, at least 50 volcanoes, including those in the Aleutian archipelago, have erupted in historical time.[6] The state accounts for ~80% of the United States' volcanoes, excluding the seamounts in the area, ~8% of world volcanoes, and most of these are located among the Aleutian Islands.[6] The Aleutian Islands arc serves as the northern boundary of the Pacific Ring of Fire,[6] where tectonic activity generates earthquakes and volcanic eruptions in masses.

The volcano is basaltic-andesitic in composition.[3] It is a modest stratovolcano,[2] rising no more than 1,683 feet (513 m) above sea level.[1] The volcanic crater is distinct, and has erupted in historical times, only "blocky" lava flows.[2] Charles Wood and Jürgen Kienle, volcanologists, propose that earlier activity, 4,000–5,000 years ago, consisted primarily of lavas of ethereal (fine) platy and thick andesite.[3] Amak Volcano is unique in that its andesitic lavas, while composed the same as the other Aleutians, contain an abundance of potash. They also could contain more sodium carbonate and rare earth element deposits than the Aleutian norm.[4] Between Bogoslof, the other Aleutian island north of the main arc, and Amak, Amak's lavas are more alkalic and silicic.[4]

Glaciation took place around the volcano roughly 6700 years BP, carving out U-shaped valleys. At the southwest flank of the island, a crater, likely a maar, can be found amid an alluvial plain.[3]

Eruptive history

The Amak Volcano has erupted three times in historical times: circa 2550 BC, from 1700–1710, and in 1796; the first of these events was identified with tephrochronology. Each eruption has been characterized by lava flows, and the two most recent eruptions included a crater eruption.[2]

See also

References

  1. 1 2 "Amak description and statistics". Alaska Volcano Observatory. United States Geological Survey. Retrieved July 6, 2009.
  2. 1 2 3 4 "Amak". Global Volcanism Program. Smithsonian Institution. Retrieved July 6, 2009.
  3. 1 2 3 4 5 Wood and Kienle, p. 51.
  4. 1 2 3 Marsh, B.D.; Leit, R.E. (November 1979). "Geology of Amak Island, Aleutian Islands, Alaska". Journal of Geology. The University of Chicago Press. 87 (6): 715–723. Bibcode:1979JG.....87..715M. doi:10.1086/628461.
  5. ↑ Ewert, John; Guffanti, Marianne; Cervelli, Peter; Quick, James (2006). "The National Volcano Early Warning System (NVEWS): U.S. Geological Survey Fact Sheet FS 2006-3142". United States Geological Survey. Retrieved July 9, 2009.
  6. 1 2 3 "Alaska GeoSurvey News: NL 2008-1". 11 (1). Alaska Division of Geological & Geophysical Surveys. March 2008: 1–14. Archived from the original on 10 August 2009. Retrieved July 9, 2009.

Bibliography

External links

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