Pavlof volcano, located on the southwestern end of the Alaska Peninsula, began erupting abruptly late March 27, 2016, sending an ash cloud to 6 km (20 000 feet) a.s.l. The last time this volcano erupted was in November 2014.
As of 00:18 UTC on March 28, ash was moving northward from the volcano.
Alaska Volcano Observatory (AVO) said seismicity began to increase from background levels at about 23:53 UTC on March 27 with quick onset of continuous tremor, which remains at high levels.
Tremor amplitude at Pavlof volcano, March 27 - 28, 2016. Image credit: USGS/AVO
AVO raised the Aviation Color Code to Red and the Volcano Alert Level to Warning.
Previous eruptions at Pavlof have produced eruptions up to 15 km (49 000 feet) a.s.l., with some drifting more than 480 km (300 miles) from the crater, according to AVO. Its staff say the volcano’s more than 40 previous eruptions have marked it as “one of the most consistently active volcanoes in the Aleutian arc.”
Pavlof volcano eruption on March 27 and 28, 2016. Image credit: USGS/AVO
The last time Pavlof was erupting was in November 2014. On November 12, 2014, AVO raised the Aviation Color Code for Pavlov to Orange and the Volcano Alert Level to Watch, citing the beginning of a new phase of eruptive activity at about 15:00 (local time). An observer in Cold Bay (52 km / 32 miles SW) reported that ash emissions rose slightly above the summit; minor ash emissions were also recorded by an FAA-operated webcam in Cold Bay beginning at 16:50. Seismicity increased and remained elevated. Lava fountaining occurred from a vent just N of the summit and flows of rock debris and ash descended the N flank. A thermal anomaly appeared in satellite images at 17:40. The eruption continued on November 14. A narrow ash plume observed in satellite images drifted 200 km (124 miles) at an altitude of 4.8 km (16 000 feet) a.s.l.
The eruption intensified on November 15 prompting AVO to raise the Aviation Color Code to Red and the Volcano Alert Level to Warning. Ash plumes rose to an altitude of 7.6 km (25 000 feet) a.s.l. and drifted 200 km NW. The intensity of seismic tremor had increased significantly. Pilot reports through 12:30 indicated that the ash plume had risen to an altitude of 9.1 km (30 000 ft) a.s.l. At about 19:00 seismicity abruptly decreased and remained low. Satellite observations confirmed a significant decrease in ash emissions; discrete seismic events possibly indicated minor ash emissions that were not detected in satellite images. The Aviation Color Code was lowered to Orange and the Volcano Alert Level was lowered to Watch. Pilot reports on November 16 indicated no eruptive activity, and satellite images showed diminished temperatures in the summit crater. During November 17 - 18 seismic activity remained at low levels and elevated surface temperatures on the upper NW flank were observed, consistent with a flow of lava and/or hot debris.
Update, March 29
At 02:01 UTC on March 29, AVO reported that the intensity of eruptive activity at Pavlof has declined significantly starting at about 22:30 UTC (March 28) and currently continuous ash emission from the summit vent is not being observed in satellite imagery. The Aviation Color Code was lowered to ORANGE and the Volcano Alert Level to WATCH.
AVO added the seismicity and infrasound signals from Pavlof have dropped to low levels and it appears that the robust eruptive activity that began yesterday has declined for now.
The level of seismic tremor is still slightly above background. A drifting ash cloud extending from the southern Bering Sea into interior Alaska is still present and may pose a hazard to air travel.
Although the intensity of the eruption has diminished, it is possible for conditions to change at any time and significant ash emissions may resume with little to no warning. At this reduced level of unrest, it is possible that low-level lava fountaining and minor amounts of ash emission may be occurring and affecting the area in the immediate vicinity of the volcano.
Pavlof volcano eruption on March 28, 2016. Image credit: Nahshon Almandmoss. Taken from Coast Guard 1713, a HC-130H Hercules based at Air Station Kodiak.
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