USGS Volcano Notice - DOI-USGS-AVO-2023-02-22T13:05:43-09:00

AVO/USGS Volcanic Activity Notice

Volcano: Aniakchak (VNUM #312090)

Current Volcano Alert Level: ADVISORY
Previous Volcano Alert Level: NORMAL

Current Aviation Color Code: YELLOW
Previous Aviation Color Code: GREEN

Issued: Wednesday, February 22, 2023, 4:43 PM AKST
Source: Alaska Volcano Observatory
Notice Number: 2023/A192
Location: N 56 deg 54 min W 158 deg 12 min
Elevation: 4400 ft (1341 m)
Area: Alaska Peninsula

Volcanic Activity Summary:

The number of earthquakes beneath Aniakchak volcano has recently increased and shifted to shallower depths. Due to this increase in seismic activity to above-background levels, the Alaska Volcano Observatory is raising the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY. There have been no signs of unrest in other monitoring data.

Background seismicity at Aniakchak has mostly been characterized by deep (>15 km or 9.3 miles), long-period events occurring at a rate of ~4 earthquakes per month. From October 2022 to present, the rate of earthquakes has been more elevated and characterized by shallower earthquakes at depths less than 9 km (5.6 miles) below sea level. The earthquake rate has further increased since January 31 with dozens of earthquakes detected per day, including a M3.7 earthquake on February 17.

There is no indication that an eruption of Aniakchak is imminent, or that one will occur. Increases in seismic activity have been detected previously at other similar volcanoes, with no subsequent eruptions. We expect additional shallow seismicity and other signs of unrest, such as gas emissions, elevated surface temperatures, and surface deformation to precede any future eruption, if one were to occur. Should activity increase, AVO will issue further notices.

AVO monitors Aniakchak with a local network, which consists of six seismometers, a web camera, and a single infrasound sensor, as well as satellite remote sensing data and regional infrasound and lightning networks. To view current monitoring data, see https://avo.alaska.edu/activity/Aniakchak.php

Recent Observations:
[Volcanic cloud height] none
[Other volcanic cloud information] none

Hazard Analysis:
[General hazards] none
[Ash cloud] none

Remarks:

Aniakchak volcano, located in the central portion of the Alaska Peninsula, consists of a stratovolcano edifice with a 10 km (6 mile) diameter summit caldera. The caldera-forming eruption occurred around 3,500 years ago. Postcaldera eruptions have produced lava domes, tuff cones, and larger spatter and scoria cone structures including Half-Cone and Vent Mountain all within the caldera. The most recent eruption occurred in 1931 and created a new vent and lava flows on the western caldera floor while spreading ash over much of southwestern Alaska. Aniakchak volcano is 25 km (15 miles) southeast of the nearest community, Port Heiden, and 670 km (416 miles) southwest of Anchorage, Alaska.

Contacts:

Michelle Coombs, Scientist-in-Charge, USGS mcoombs@usgs.gov (907) 786-7497

Társilo Girona, Acting Coordinating Scientist, UAFGI tarsilo.girona@alaska.edu (907) 322-4085

Next Notice:

A new VAN will be issued if conditions change significantly or alert levels are modified. While a VAN is in effect, regularly scheduled updates are posted at http://www.avo.alaska.edu.

The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.

(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:	(20230223/0143Z)
(3) Volcano:	Aniakchak (VNUM #312090)
(4) Current Color Code:	YELLOW
(5) Previous Color Code:	GREEN
(6) Source:	Alaska Volcano Observatory
(7) Notice Number:	2023/A192
(8) Volcano Location:	N 56 deg 54 min W 158 deg 12 min
(9) Area:	Alaska Peninsula
(10) Summit Elevation:	4400 ft (1341 m)
(11) Volcanic Activity Summary:	The number of earthquakes beneath Aniakchak volcano has recently increased and shifted to shallower depths. Due to this increase in seismic activity to above-background levels, the Alaska Volcano Observatory is raising the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY. There have been no signs of unrest in other monitoring data. Background seismicity at Aniakchak has mostly been characterized by deep (>15 km or 9.3 miles), long-period events occurring at a rate of ~4 earthquakes per month. From October 2022 to present, the rate of earthquakes has been more elevated and characterized by shallower earthquakes at depths less than 9 km (5.6 miles) below sea level. The earthquake rate has further increased since January 31 with dozens of earthquakes detected per day, including a M3.7 earthquake on February 17. There is no indication that an eruption of Aniakchak is imminent, or that one will occur. Increases in seismic activity have been detected previously at other similar volcanoes, with no subsequent eruptions. We expect additional shallow seismicity and other signs of unrest, such as gas emissions, elevated surface temperatures, and surface deformation to precede any future eruption, if one were to occur. Should activity increase, AVO will issue further notices. AVO monitors Aniakchak with a local network, which consists of six seismometers, a web camera, and a single infrasound sensor, as well as satellite remote sensing data and regional infrasound and lightning networks. To view current monitoring data, see https://avo.alaska.edu/activity/Aniakchak.php
(12) Volcanic cloud height:	none
(13) Other volcanic cloud information:	none
(14) Remarks:	Aniakchak volcano, located in the central portion of the Alaska Peninsula, consists of a stratovolcano edifice with a 10 km (6 mile) diameter summit caldera. The caldera-forming eruption occurred around 3,500 years ago. Postcaldera eruptions have produced lava domes, tuff cones, and larger spatter and scoria cone structures including Half-Cone and Vent Mountain all within the caldera. The most recent eruption occurred in 1931 and created a new vent and lava flows on the western caldera floor while spreading ash over much of southwestern Alaska. Aniakchak volcano is 25 km (15 miles) southeast of the nearest community, Port Heiden, and 670 km (416 miles) southwest of Anchorage, Alaska.
(15) Contacts:	Michelle Coombs, Scientist-in-Charge, USGS mcoombs@usgs.gov (907) 786-7497 Társilo Girona, Acting Coordinating Scientist, UAFGI tarsilo.girona@alaska.edu (907) 322-4085
(16) Next Notice:	A new VAN will be issued if conditions change significantly or alert levels are modified. While a VAN is in effect, regularly scheduled updates are posted at http://www.avo.alaska.edu.