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Aniakchak
Description
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Facts
Official Name:
Aniakchak Crater
Seismically Monitored:
Yes
Color Code:
UNASSIGNED
Alert Level:
UNASSIGNED
Elevation:
1341m (4399ft)
Latitude:
56.9058
Longitude:
-158.209
Smithsonian VNum:
312090
Pronunciation:
Your browser does not support the audio element.
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
Pilot Point 51 mi (82 km)
NE
Distance from Anchorage: 419 mi (674 km)
Subfeatures:
Vent Mtn
Surprise Lake
Blocky cone
Bolshoi Dome
Half Cone
New cone
Pumice Dome
Vulcan Dome
West Dome
1931 Crater
Description
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.”
Name Origin
Sargent and Smith (1922) named Aniakchak Crater and Aniakchak peak. The name was probably derived from nearby Aniakchak Bay (Orth, 1971).
References Cited
[1]
Catalog of the historically active volcanoes of Alaska
, 1998
Miller, 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.
title page PDF
52
intro and TOC PDF
268 KB
eastern part - Wrangell to Ukinrek Maars PDF
972 KB
central part - Chiginagak to Cleveland PDF
2,463 KB
western part - Carlisle to Kiska PDF
956 KB
references PDF
43 KB
[2]
Aniakchak crater, Alaska Peninsula
, 1925
Smith, 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.
full-text PDF
1.2 MB
[3]
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.
Link to free map online
[4]
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/
link to PDFs and tables on USGS website
[5]
Late Quaternary caldera-forming eruptions in the eastern Aleutian arc, Alaska
, 1987
Miller, 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.
full-text PDF
2.5 MB
[6]
Spectacular mobility of ash flows around Aniakchak and Fisher calderas, Alaska
, 1977
Miller, 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.
full-text PDF
1.92 MB
Current Activity
No new updates for Aniakchak volcano since February 18, 2026, 11:48 am.
Recent Updates
Monitoring status of Aniakchak Volcano remains at UNASSIGNED
Feb 18th, 2026 11:48:22 AM
Resuspended ash observed from Aniakchak. Aviation color code and alert level remain at UNASSIGNED.
Jan 15th, 2026 05:47:25 PM
Status changed to Unmonitored due to seismic station outages.
Dec 23rd, 2025 11:23:05 AM
Monitoring stations online again, Aviation Color Code and Volcano Alert Level changed to GREEN/NORMAL.
Jul 8th, 2024 12:52:29 PM
Aviation Color Code and Volcano Alert Level decreased to UNASSIGNED/UNASSIGNED due to failure of monitoring equipment.
Oct 30th, 2023 02:14:09 PM
Webcams
Aniakchak [ANNQ, 1217 ft]
Aniakchak [Port Heiden, 59 ft]
Port Heiden - E
Webicorder
Color Code Timeline
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Before an eruption
Sign up for volcanic activty alerts from the Volcano Notification System (US Geological Survey)
Preliminary volcano-hazard assessment for Aniakchak volcano, Alaska
Ashfall & Preparedness Information
Ashfall impacts & preparedness (US Geological Survey)
Volcanic health hazards & impacts (International Volcanic Health Hazards Network)
Ash Alert! Pamphlet (AK Division of Homeland Security & Emergency Management)
Volcanic Ashfall (AK Department of Environmental Conservation, Division of Air Quality)
During and After an Eruption
National Weather Service Ashfall Warnings are posted here when in effect
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Other Useful Links
Citizen Science: Ashfall collection instructions
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Ash Forecasting
Mathematical models developed by the USGS forecast various aspects of how a volcanic ash plume will interact with wind—where, how high, and how fast ash particles will be transported in the atmosphere, as well as where ash will fall out and accumulate on the ground. AVO runs these models when a volcano is restless by assuming a reasonable hypothetical eruption, to provide a pre-eruptive forecast of areas likely to be affected. During an ongoing eruption, AVO will update the forecast with actual observations (eruption start time and duration, plume height) as they become available.
View the current airborne ash cloud models for Aniakchak
Ashfall thickness forecast
The Ash3d model was developed by the USGS to forecast how a volcanic ash plume will interact with wind and where ash will fall out and accumulate on the ground. AVO runs these models twice daily when a volcano is restless by assuming a reasonable
hypothetical
eruption altitude and duration. The map shows the model results of ashfall thickness for areas that are likely to be affected, if one were to occur. During an ongoing eruption, AVO will update the forecast with actual observations (eruption start time and duration, plume height) as they become available, and these plots will be automatically updated. The
National Weather Service
Anchorage Forecast Office will issue the official ashfall warning product and post them at
weather.gov/afc
THESE PRODUCTS MAY NOT BE CURRENT.
During an actual eruption, see National Weather Service forecasts of ashfall:
Ashfall Forecast
Click on the X on the graphic (upper right) to expand the map to show the map legend.
Ashfall Start Time
This map shows the modeled estimate of the time it would take for ashfall to begin following an eruption. It corresponds to the ashfall thickness forecast map shown above. This map uses the start time of either the twice-daily hypothetical model runs (time shown in the legend) or the actual eruption start time (if one were to occur). In the case of an actual eruption, the National Weather Service Anchorage Forecast Office will issue the official ashfall warning product that includes the ashfall start time and post them at
weather.gov/afc
THESE PRODUCTS MAY NOT BE CURRENT.
During an actual eruption, see National Weather Service forecasts of ashfall:
Ashfall Start Times Forecast
Click on the X on the graphic (upper right) to expand the map to show the map legend.
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