Small explosion signals at Pavlof volcano, alerts raised, Alaska

Small explosion signals from Pavlof volcano have been detected on the infrasound network located at Sand Point and on the local seismic network on October 19, 2019.

It is unknown if the explosions produced any volcanic ash, but their small size suggests any hazard is currently confined to the area around the volcano's summit, the Alaska Volcano Observatory (AVO) reports.

Because these signals are above normal background for Pavlof, AVO is raising the Aviation Color Code to YELLOW and the Alert Level to ADVISORY.

Low-frequency seismic tremor and vigorous steam plume have been observed at Pavlof volcano, Alaska on May 14 and 15, 2019.

"While this does not mean that an eruption is likely or imminent, past eruptions of Pavlof occurred with little or no warning," AVO said at the time.

The last known eruption at this volcano took place in 2016 (VEI 2).

Geological summary

The most active volcano of the Aleutian arc, Pavlof is a 2 519-m-high (8 264 feet) Holocene stratovolcano that was constructed along a line of vents extending NE from the Emmons Lake caldera.

Pavlof and its twin volcano to the NE, 2 142-m-high (7 027 feet) Pavlof Sister, form a dramatic pair of symmetrical, glacier-covered stratovolcanoes that tower above Pavlof and Volcano bays.

A third cone, Little Pavlof, is a smaller volcano on the SW flank of Pavlof volcano, near the rim of Emmons Lake caldera.

Unlike Pavlof Sister, Pavlof has been frequently active in historical time, typically producing Strombolian to Vulcanian explosive eruptions from the summit vents and occasional lava flows. The active vents lie near the summit on the north and east sides.

The largest historical eruption took place in 1911, at the end of a 5-year-long eruptive episode, when a fissure opened on the N flank, ejecting large blocks and issuing lava flows. (GVP)

Featured image credit: USGS/AVO, David Fee