Vigorous steam degassing was observed at Alaska's Pavlof volcano in web camera images from Cold Bay (65 km / 35 miles SW) and Black Hills (35 km / 20 miles NNE) on July 28, 2016. Alaska Volcano Observatory (AVO) has increased the Aviation Color Code and the Volcano Alert Level to ORANGE/WATCH.
AVO said satellite observations and pilot reports indicate minor amounts of ash associated with the steam cloud at an altitude of less than 4.5 km (15 000 ft) above sea level.
Seismicity remains elevated, with periods of volcanic tremor continuing.
Activity is currently at relatively low levels. However, an increase in eruptive activity is possible and could occur with little or no warning.
Pavlof on July 28, 2016. Credit: USGS/AVO
Meanwhile, unrest at Alaska's Cleveland volcano continues. Satellite and web camera observations are currently obscured by clouds, but no significant activity is being observed in seismic or infrasound (pressure sensor) data.
Other Alaska volcanoes show no signs of significant unrest.
The most active volcano of the Aleutian arc, Pavlof is a 2519-m-high 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, 2142-m-high 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