Lava continued to erupt within the summit crater of Great Sitkin at a low rate over the past week. Weather conditions were cloudy at the volcano for most of the week obscuring views of the summit. Satellite-based radar data from February 19 showed that the lava flow continued advancing to the east into the remaining summit crater icefield. There is also a smaller lobe slowly advancing to the south that is nearing the crater rim where lava previously spilled down the southwest flank in 2021–2022. Small earthquakes were detected on some days, but seismic activity overall remains very low.  

Great Sitkin is monitored by local seismic and infrasound sensors, satellite data, web cameras, and regional infrasound and lightning networks.  

Earthquake activity beneath Trident Volcano has recently increased and is ongoing, although there have been no signs of unrest in other monitoring data. Due to this increase in seismic activity to above-background levels, the Alaska Volcano Observatory raised the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY on Wednesday, February 22. Over the past week, seismicity has been elevated at Trident Volcano, with dozens of earthquakes detected per day, many too small to locate. The largest of these was a M4 that occurred this morning. No significant activity was seen in partly cloudy satellite and web camera views all week. 

The current period of seismic unrest began on August 24, 2022. Earthquake depths at the beginning of the swarm were mostly deep, around 25 km (16 miles) below sea level, and became progressively shallower to around 5 km (3 miles) over the following four days. Since late August 2022, most earthquakes have been located in the shallow crust, with depths less than 6 km below sea level. Since January 1, 2023, earthquakes under Trident are occurring at an average rate of about ten per day.   

Increases in seismic activity have been detected previously at Trident Volcano and 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.  

AVO monitors Trident Volcano with a local network of seismometers, a webcam, remote sensing data, and regional infrasound and lightning networks. 

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 raised the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY on Wednesday, February 22. Dozens of small earthquakes were detected daily over the past week, but no significant activity was observed in partly cloudy web camera or cloudy satellite views. 

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.  

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. 

No unusual activity was observed in seismic or infrasound data over the past week. Steam emissions were seen in the north cone of Mount Young in partly cloudy web camera views all week, but satellite views were mostly obscured by clouds. 

Although the active north cone of Mount Young continues to produce a robust steam plume when views are clear, no ash emissions or explosive activity have been detected at Semisopochnoi volcano since late January. The level of seismic activity has also decreased, with no significant seismic tremor observed since January 25th. The Alaska Volcano Observatory therefore lowered the Aviation Color Code to YELLOW and Volcano Alert Level to ADVISORY on Wednesday, February 22. 

Small eruptions producing minor ash deposits within the vicinity of the active north crater of Mount Young and ash clouds usually under 10,000 ft (3 km) above sea level have characterized the recent activity. Additional ash-producing events could occur again with little warning.  
 
Semisopochnoi volcano is monitored by local seismic and infrasound sensors, satellite data, web cameras, and regional infrasound and lightning networks. 

The ongoing earthquake swarm near Takawangha volcano continues, with more than 300 earthquakes located during the past week. The number of events per day was highest during the first half of the week, with seismic activity decreasing over the past several days. No eruptive signals were detected in seismic or satellite data. Weather conditions were mostly cloudy all week obscuring satellite views of the volcano. 

Takawangha is monitored with a local seismic network, a single local infrasound sensor, regional infrasound and lightning sensors, and satellite imagery.