The recent eruption of Shishaldin Volcano has decreased in intensity, leading to a reduction in the Aviation Color Code and Volcano Alert Level.
According to current observations by the Alaska Volcano Observatory, the volcano is still emitting low-level ash below 10,000 feet above sea level, with ash drifting to the south. The Aviation Color Code has been downgraded to orange, and the Volcano Alert Level has been lowered to watch.
On Tuesday, a significant ash plume was detected, starting at approximately 7 am AKDT (15:00 UTC), reaching an altitude of around 30,000 feet above sea level.
By 9:30 am AKDT (17:30 UTC), satellite data revealed that the primary plume had detached, but residual low-level ash was still emanating. The detached plume remains visible between 60 and 280 miles away from the volcano. In response to this cloud, the National Weather Service has issued a SIGMET (Significant Meteorological Information) advisory.
Explosive eruptive activity can resume rapidly and with little warning. Previous eruptions of Shishaldin have produced minor to significant ash clouds. Consequently, the volcano is closely monitored using local seismic and infrasound sensors, web cameras, and a telemetered geodetic network.
While the local monitoring network is partially impaired, the Alaska Volcano Observatory is employing nearby geophysical networks, satellite data, and regional infrasound and lighting data to detect any signs of activity. AVO will continue to closely monitor the volcanic unrest at Shishaldin.
Hazard analysis reveals that there is a possibility of trace ashfall downwind of the volcano, while mud flows are likely to occur on all flanks, the observatory said.
Shishaldin Volcano is situated near the center of Unimak Island in the eastern Aleutian Islands. A visually striking, symmetric cone, it has a base diameter of approximately 10 miles. Its funnel-shaped summit crater measures 660 feet wide and typically emits a steam plume and occasional small amounts of ash.
Shishaldin is one of the most active volcanoes in the Aleutian volcanic arc, having experienced at least 54 episodes of unrest, including over 26 confirmed eruptions since 1824.
While most eruptions have been relatively small, the April-May 1999 event produced an ash column that reached a height of 45,000 ft above sea level.
As observers monitor the situation, residents and pilots are warned by the FAA to steer clear of the area through Aug. 14. Shishaldin is about 58 miles from the Cold Bay airport, which also serves King Cove and neighboring villages and towns.
