Shishaldin Volcano Erupts on Aleutian Island of Unimak Setting Off Aviation Red Alert
The Alaska Volcano Observatory issued a notice of increased eruptive activity today and warns that pyroclastic and mudflows are likely - ashfall will affect surrounding fishing villages
Shishaldin Volcano began a renewed eruption this morning around 5:42 am AKDT, shooting an ash cloud growing above 20,000 feet (6 km) above sea level along with volcanic lightning detections. This follows an increase in observed eruptive activity over the past two days. The volcano recently erupted on September 15, just 10 days ago, when the Alaska Volcano Observatory (AVO) also issued a red alert.
In response to today’s Shishaldin eruption, the Aviation Color Code is being raised to RED again and the Volcano Alert Level is being raised to WARNING by the AVO. The National Weather Service has issued a SIGMET (Significant Meteorlogical Information) for this ash cloud, and a Special Weather Statement has been issued for possible trace ash on False Pass.
The AVO reports that based on previous eruption cycles, significant ash emissions are likely to continue for several hours. Pyroclastic and mudflows are likely on the immediate flanks of the volcano.
Recent significant ash events during the current eruption resulted in ash clouds with heights up to 40,000 ft (12 km) above sea level.
On September 15, an explosive eruption from Shishaldin began around 5:10 p.m. AKDT following a several-hour increase in seismicity. Ash was emitted and drifted to the east below the cloud deck of 27,000 feet above sea level. The Aviation Color Code and Volcano Alert Level issued at that time was RED/WARNING.
At least seven other volcanic eruptions of Shishaldin causing Red Alerts and Warnings to be issued have taken place since January 2023. Today’s volcanic activity is the latest in a series of consistent eruptions since July 2023.
Shishaldin Volcano is monitored by local seismic and infrasound sensors, web cameras, and a telemetered geodetic network. In addition to the local monitoring network, AVO uses nearby geophysical networks, regional infrasound and lighting data, and satellite images to detect eruptions.
Shishaldin is located near the center of Unimak Island in the eastern Aleutian Islands, just east of the international fishing port of Dutch Harbor/Unalaska. The volcano is an impressive symmetric cone with a base diameter of approximately 10 miles (16 km). A 660 foot (200 m) wide funnel-shaped summit crater regularly emits a steam plume and occasional small amounts of ash. Shishaldin is one of the most active volcanoes in the Aleutian volcanic arc, with at least 54 volcanic activity events including over 26 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.