The explosive activity at the volcano has been continuing at intense levels over the past few hours yesterday.
Near-constant ash emissions persisted from the recently formed cinder cone within the summit crater for over 6 hours, accompanied by the ongoing seismic tremor. The eruptive period that began at 21:00 local time sent emissions of ash to an approx. elevation varying between 15,000 ft (4,6 km) and 16,000 ft (4.9 km), some of them reaching up to 20,000 ft (6 km) height. The ash column has extended about 125 km to the S-SE of the volcano, but later on has changed its direction to E-SE. The NWS has a SIGMET for this cloud and estimate it to be under 16,000 ft (4.9 km) above sea level. Frequent explosion signals were being detected at regional infrasound (pressure sensor) networks.
Therefore, the Alaska Volcano Observatory (AVO) raised the alert status for the volcano to „Red“.
The recent magnitude 7.3 earthquake located 55 mi (89 km) SW of Sand Point has nothing to do with the volcanic activity at Shishaldin volcano.
Eruptions from Shishaldin have produced minor and on occasion significant ash clouds in the past. These can occur with little warning. Shishaldin is monitored by local seismic and infrasound sensors, web cameras, and a telemetered geodetic network. The local monitoring network is partially impaired, therefore AVO is also using nearby geophysical networks, satellite data and regional infrasound and lighting data to detect activity.
UPDATE
Today, the AVO reported that the explosive eruption at the volcano has declined along with the seismic activity and no explosion signals are being detected in infrasound (pressure sensor) data.
Hence, the local institute decreased the alert level for the volcano back to „Orange“.
Source: Alaska Volcano Observatory volcano activity update 16 July 2023
