USGS Volcano Notice - DOI-USGS-AVO-2024-03-29T00:35:15+00:00

ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, March 29, 2024, 9:25 AM AKDT (Friday, March 29, 2024, 17:25 UTC)

ATKA VOLCANIC COMPLEX (VNUM #311160)
52°19'51" N 174°8'20" W, Summit Elevation 5030 ft (1533 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

A small explosion occurred at the summit of Korovin volcano, one of the volcanoes in the Atka volcanic complex, on Wednesday March 27 at 19:36 AKDT (03:36 UTC March 28). It was detected in local infrasound and seismic data and was followed by a few minutes of elevated seismic tremor. Since then, seismic activity has continued to be above background. Satellite and web-camera views have been mostly obscured by clouds since the explosion, but a few clearer looks suggest that it did not produce significant ash.

AVO increased the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY Wednesday following the explosion. AVO continues to carefully monitor for signs of additional unrest that could lead to an eruption. The Atka volcanic complex is monitored by local seismic and infrasound sensors and webcam, satellite data, and regional lightning detection instruments.

The Atka volcanic complex forms the northern part of Atka Island, located about 16 km north of the community of Atka and 1,761 km southwest of Anchorage. The Atka volcanic complex includes a possible older caldera and several younger vents, including Korovin Volcano, Mount Kliuchef, and Sarichef Volcano. Korovin Volcano, a 1553-m-high (5030 ft) stratovolcano, has been the site of most historical volcanic activity, and has a small, roiling crater lake that occasionally produces energetic steam emissions. Korovin has erupted several times in the past 200 years, including 1973, 1987, and 1998, and has likely had small ash emissions as recently as 2005. Typical recent Korovin eruptions produce minor amounts of ash and occasional but small lava flows. Reports of the height of the ash plume produced by the 1998 eruption ranged as high as 10,600 m (35,000 feet) above sea level. Mount Kliuchef is composed of a series of five vents aligned northeast–southwest. The two main summit vents of Kliuchef appear relatively young and the easternmost was probably the source of an 1812 eruption that is sometimes attributed to Sarichef.

GREAT SITKIN (VNUM #311120)
52°4'35" N 176°6'39" W, Summit Elevation 5709 ft (1740 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

The eruption of lava within the summit crater of Great Sitkin Volcano continues. Partly cloudy satellite imagery showed steaming and elevated surface temperatures from the active lava flow. The active northwestern lava flow lobe that started in January 2024 is warm and mostly snow-free. Satellite radar data through March 28 showed growth of the northwest lava flow, as well as uplift of the lava flow surface above the vent region. Seismic activity remains low with occasional small volcanic earthquakes.

The current prolonged period of lava eruption at Great Sitkin Volcano began in July 2021. No explosive events have occurred since a single event in May 2021.        

The volcano is monitored by local seismic, geodetic, and infrasound sensors and web cameras, as well as regional infrasound and lightning networks and satellite data.   

Great Sitkin Volcano is a basaltic andesite volcano that occupies most of the northern half of Great Sitkin Island, a member of the Andreanof Islands group in the central Aleutian Islands. It is located 26 miles (43 km) east of the community of Adak. The volcano is a composite structure consisting of an older dissected volcano and a younger parasitic cone with a ~1 mile (1.5 km)-diameter summit crater. A steep-sided lava dome, emplaced during the 1974 eruption, occupies the center of the crater. That eruption produced at least one ash cloud that likely exceeded an altitude of 25,000 ft (7.6 km) above sea level. A poorly documented eruption occurred in 1945, also producing a lava dome that was partially destroyed in the 1974 eruption. Within the past 280 years a large explosive eruption produced pyroclastic flows that partially filled the Glacier Creek valley on the southwest flank.

SHISHALDIN (VNUM #311360)
54°45'19" N 163°58'16" W, Summit Elevation 9373 ft (2857 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Low-level unrest continues at Shishaldin Volcano. Seismicity was at low levels throughout the week with small earthquakes and weak seismic tremor observed. Weak infrasound was detected on a couple days in quiet conditions and likely results from gas bubbles bursting deep within the volcanic crater.  Satellite and webcam views were mostly obscured by clouds during the week, but a few clear webcam views showed little to no steaming at the summit. Low-level sulfur dioxide emissions were observed in clear satellite views on March 25. Minor rock falls or collapse events from the unstable ground in and near the summit crater remain likely. These events may generate very small clouds of fine-grained ash that dissipate quickly in the immediate vicinity of the summit. 

No significant eruptive activity has occurred since November 2023.  

Local seismic and infrasound sensors, web cameras, and a geodetic network are used to monitor Shishaldin Volcano. In addition to the local monitoring network, AVO uses nearby geophysical networks, regional infrasound and lighting data, and satellite images to monitor the volcano.

Shishaldin volcano, located near the center of Unimak Island in the eastern Aleutian Islands, is a spectacular symmetric cone with a base diameter of approximately 10 miles (16 km). It is one of the most active volcanoes in the Aleutian volcanic arc, with at least 54 episodes of unrest including over 28 confirmed eruptions since 1824. Most eruptions are relatively small, although the April-May 1999 event generated an ash column that reached 45,000 ft. (14 km) above sea level.

CONTACT INFORMATION:

Matt Haney, Scientist-in-Charge, USGS mhaney@usgs.gov (907) 786-7497

David Fee, Coordinating Scientist, UAFGI dfee1@alaska.edu (907) 378-5460

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.