Pavlof

Lava continues to slowly erupt within the summit crater at Great Sitkin Volcano. Satellite data on January 18 confirmed this by showing active steaming from the central region of the summit dome. Satellite data on January 22 shows that this area is largely snow-free, while the rest of the dome is covered in snow. Clouds obscured webcam images of the volcano with the exception of January 22. Seismic activity remains low, with only occasional small earthquakes and rockfalls detected. 

The current eruption of lava began in July 2021 and has filled most of the summit crater and advanced into valleys below. There have been no explosions at Great Sitkin Volcano since an event in May 2021. The volcano is monitored using local seismic and infrasound sensors, satellite data and web cameras, and regional infrasound and lightning networks. 

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 (42 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 (1.6 km)-diameter summit crater. A steep-sided lava dome, emplaced in the crater during an eruption in 1974, has been mostly buried by the ongoing eruption. The 1974 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 also occurred in 1945, 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.

Matt Haney, Scientist-in-Charge, USGS [email protected] (907) 786-7497

David Fee, Coordinating Scientist, UAFGI [email protected] (907) 378-5460

Contact AVO: https://avo.alaska.edu/contact

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.

The period of elevated seismic activity that prompted an increase in Pavlof's alert level on January 14 decreased to background levels this week. As a result, AVO lowered the Aviation Color Code to GREEN and the Volcano Alert Level to NORMAL on January 21. Seismicity remains low and no eruptive activity or unusual surface temperatures have been observed. 

Increases in this type of earthquake activity in the past have preceded eruptions, but also have ended without an eruption occurring. Eruptions at Pavlof Volcano have also occurred with little or no precursor activity. 

The Alaska Volcano Observatory will continue to closely monitor Pavlof Volcano data to confirm if the period of elevated activity has ended. The volcano is monitored by local seismic and infrasound sensors, satellite data, web cameras, and regional infrasound and lightning networks.

Pavlof Volcano is a snow- and ice-covered stratovolcano located on the southwestern end of the Alaska Peninsula about (592 miles (953 km) southwest of Anchorage. The volcano is about 4.4 miles (7 km) in diameter and has recently active vents on the north and east sides close to the summit. With over 40 historic eruptions, it is one of the most consistently active volcanoes in the Aleutian arc. Eruptive activity is generally characterized by sporadic Strombolian lava fountaining continuing for a several-month period. Ash plumes as high as 49,000 ft above sea level have been generated by past eruptions of Pavlof, and during the March 2016 eruption, ash plumes as high as 40,000 ft above sea level were generated and the ash was tracked in satellite data as distant as eastern Canada. The nearest community, King Cove, is located 30 miles (48 km) to the southwest of Pavlof.

Matt Haney, Scientist-in-Charge, USGS [email protected] (907) 786-7497

David Fee, Coordinating Scientist, UAFGI [email protected] (907) 378-5460

Contact AVO: https://avo.alaska.edu/contact

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.

Signs of volcanic unrest at Shishaldin Volcano continued this week. Satellite imagery showed barely elevated surface temperatures on January 19, 21, and 23, likely related to the continued gas emissions at the summit and favorable atmospheric conditions. Web camera images, when clear, showed a plume of gas rising from the summit crater. Low-level seismic activity has persisted, with volcanic tremor and small earthquakes occurring frequently. Infrasound signals, likely caused by gas bubbles bursting deep within the volcanic vent, were also detected throughout the week when the conditions were not too windy. At this time, there is no evidence of lava at the surface. 

Shishaldin Volcano is monitored by local seismic and infrasound sensors, web cameras, and a telemetered geodetic network. In addition to the local monitoring network, the Alaska Volcano Observatory uses nearby geophysical networks, regional infrasound and lighting data, and satellite data to monitor the volcano. 

Shishaldin Volcano, located near the center of Unimak Island in the eastern Aleutian Islands, is a conical stratovolcano 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 activity during the 1999 and 2023 eruptions generated ash columns that reached between up to 46,000 ft (16 km) above sea level.

Matt Haney, Scientist-in-Charge, USGS [email protected] (907) 786-7497

David Fee, Coordinating Scientist, UAFGI [email protected] (907) 378-5460

Contact AVO: https://avo.alaska.edu/contact

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.