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Aniakchak Crater description and information




Official Name: Aniakchak Crater
Type:Stratovolcano with summit caldera, intracaldera domes, cones, and vents
Most Recent Activity:May 1, 1931
Seismically Monitored: No
Elevation: 4400 ft (1341 m)
Latitude: 56.9058° N
Longitude:158.209° W
CAVW Number:312090
Pronunciation: Sound file
Associated Features:Vent Mtn
Surprise Lake
Blocky cone
Bolshoi Dome
Half Cone
New cone
Pumice Dome
Vulcan Dome
West Dome
1931 Crater
Nearby towns:Port Heiden 16 mi (26 km) NW
Chignik 43 mi (69 km) SW
Chignik Lagoon 43 mi (69 km) SW
Chignik Lake 50 mi (80 km) SW
Anchorage 419 mi (674 km) NE
From Miller and others (1998) [1]: "Aniakchak Crater is an ice-free, circular caldera about 10 km in diameter and a maximum of 1 km deep which was first described by Smith (1925) [2]. The pre-caldera cone was built upon a basement of Tertiary sedimentary and volcanic rocks and Jurassic-Cretaceous sedimentary rocks, which are exposed high on the east and south walls of the caldera [3]. The elevation of the caldera rim varies from 1,341 m to 610 m. Surprise Lake, a 3.2-km-long lake in the northeast part of the caldera at an elevation of about 335 m is the source of the Aniakchak River, which flows through a breach in the eastern wall of the caldera. Numerous domes, flows, and cones occupy the interior of the caldera [4]; the largest cone is Vent Mountain, 2.5 km in diameter and rising 430 m above the floor of the caldera. The pre-caldera cone was built on the west side of a basement high. The cone was deeply dissected by numerous glaciers that cut U-shaped valleys into the slopes before the caldera-forming eruption.

From Bacon and others (2014) [4]: “The oldest recognized postglacial explosive eruption, andesitic Aniakchak I, left nonwelded ignimbrite in valleys below the edifice and fines-poor welded ignimbrite or agglutinated fall deposits high on its flanks between ca. 9,500 and 7,000 years ago. A small caldera may have collapsed at the source of the ignimbrite, likely just west of the present Vent Mountain…Subsequent to Aniakchak I, Plinian eruptions ca. 7,000 14C yr B.P. from a vent northeast of the edifice summit produced the Black Nose Pumice, consisting of a lower unit of rhyodacite lava, pumice fall, and intraplinian welded ignimbrite and an upper unit of dacite pumice fall and northeast flank lava flow. At least 20 additional Holocene eruptions are thought to have occurred before the Aniakchak II caldera-forming event.”

From Miller and others (1999) [1]: "Ash flows from the caldera-forming eruption - 3430 +/- 10 yrs B.P. [5] - reached both the Bering Sea and the Pacific Ocean [6]. They are typically non-welded and fill glacial valleys to a depth of at least 75 m adjacent to the caldera rim. The ash flows were highly mobile, over-running 260-meter-high passes in the Aleutian Range and traveling as far as 50 km from the caldera rim [6]."

From Bacon and others (2014) [4]: “Postcaldera vents are mainly on the caldera ring-fracture system. The earliest extruded small dacite domes into a deep caldera lake and a lava flow on the northwest flank. Three basaltic andesite-andesite tuff cones were constructed on the eastern caldera floor after catastrophic draining of the lake by ~200 m. Dacite-andesite magmas issued from Vent Mountain and Half Cone starting as early as ~1,000 years ago. Plinian eruption at Half Cone ~400 14C yr B.P. yielded widespread dacite Pink and overlying andesite Brown Pumice fall deposits. Strombolian eruption of basaltic andesite built Blocky Cone after Half Cone and most Vent Mountain activity. The most recent eruption, in 1931, yielded dacite-rhyodacite tephra followed by relatively voluminous andesite tephra and ended with minor basaltic andesite.”

Catalog of the historically active volcanoes of Alaska, 1998
citation imageMiller, T. P., McGimsey, R. G., Richter, D. H., Riehle, J. R., Nye, C. J., Yount, M. E., and Dumoulin, J. A., 1998, Catalog of the historically active volcanoes of Alaska: U.S. Geological Survey Open-File Report 98-0582, 104 p.
Download PDF title page PDF : 52
Download PDF intro and TOC PDF : 268 KB
Download PDF eastern part - Wrangell to Ukinrek Maars PDF : 972 KB
Download PDF central part - Chiginagak to Cleveland PDF : 2,463 KB
Download PDF western part - Carlisle to Kiska PDF : 956 KB
Download PDF references PDF : 43 KB

Aniakchak crater, Alaska Peninsula, 1925
citation imageSmith, W. R., 1925, Aniakchak crater, Alaska Peninsula: in Mendenhall, W. C., (ed.), Shorter contributions to general geology, U.S. Geological Survey Professional Paper PP 0132-J, p. 139-149, 4 plates, scale unknown.
Download PDF full-text PDF : 1.2 MB

Geologic map of the Chignik and Sutwik Island quadrangles, Alaska, 1981
Detterman, R. L., Miller, T. P., Yount, M. E., and Wilson, F. H., 1981, Geologic map of the Chignik and Sutwik Island quadrangles, Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I 1229, unpaged, 1 sheet, scale 1:250,000.

Postglacial eruptive history, geochemistry, and recent seismicity of Aniakchak Volcano, Alaska, 2014
Bacon, C.R., Neal, C.A., Miller, T.P., McGimsey, R.G., and Nye, C.J., 2014, Postglacial eruptive history, geochemistry, and recent seismicity of Aniakchak Volcano, Alaska: U.S. Geological Survey Professional Paper 1810, 74 p., http://dx.doi.org/10.3133/pp1810, available online at http://pubs.usgs.gov/pp/1810/
Download link to PDFs and tables on USGS website

Late Quaternary caldera-forming eruptions in the eastern Aleutian arc, Alaska, 1987
citation imageMiller, T. P., and Smith, R. L., 1987, Late Quaternary caldera-forming eruptions in the eastern Aleutian arc, Alaska: Geology, v. 15, n. 5, p. 434-438.
Download PDF full-text PDF : 2.5 MB

Spectacular mobility of ash flows around Aniakchak and Fisher calderas, Alaska, 1977
citation imageMiller, T. P., and Smith, R. L., 1977, Spectacular mobility of ash flows around Aniakchak and Fisher calderas, Alaska: Geology, v. 5, n. 3, p. 173-176.
Download PDF full-text PDF : 1.92 MB

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