Low-frequency seismic tremor and vigorous steam plume have been observed at Pavlof volcano, Alaska over the past 2 days, forcing the Alaska Volcano Observatory (AVO) to raise the Aviation Color Code and Alert Level to Yellow/Advisory on May 15, 2019.
The low-frequency tremor was observed on May 14, followed by vigorous steam plume on the morning of May 15 (LT).
"This represents an increase from background activity and we are increasing the Aviation Color Code and Alert Level to YELLOW/ADVISORY," AVO said 22:22 UTC, May 15.
While this does not mean that an eruption is likely or imminent, past eruptions of Pavlof occurred with little or no warning.
The last eruption of this volcano took place in 2016 (VEI 2).
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, Dave Clum
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