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ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, April 1, 2016, 2:44 PM AKDT (Friday, April 1, 2016, 22:44 UTC)
55°25'2" N 161°53'37" W,
Summit Elevation 8261 ft (2518 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE
The explosive eruption that began on Sunday, March 27, declined significantly the following day and has continued over the past week at a diminished level of intensity. Seismic activity remains elevated at levels above background and over the past 24 hours has been characterized by occasional small earthquakes and intermittent volcanic tremor. No ash emissions or elevated surface temperatures have been observed in cloudy satellite and web camera views over the past day.
The ash-producing energetic phase of the eruption lasted from 4 PM AKDT (00:00 UTC) on Sunday until about 12:30 PM AKDT (20:30 UTC) on Monday, and produced an ash cloud that stretched northeast over Bristol Bay and interior Alaska for over 1200 km (750 miles). Numerous pilot reports placed the top of the cloud at 30,000 to 37,000 ft above sea level, consistent with satellite data. Lava fountaining from the summit crater was observed on Sunday night by mariners, pilots, and by residents in Cold Bay, located 37 miles (60 km) to the SW. Minor ashfall (1/32 to 1/4 in) was reported in the nearby community of Nelson Lagoon and trace ashfall (less than 1/32 in) was confirmed near Dillingham in southwest Alaska. Periods of low-level ash emission and somewhat elevated seismicity persisted overnight Monday, but decreased during the early morning hours on Tuesday. By Wednesday, the drifting, remnant ash cloud from the energetic phase of the eruption had dispersed over Alaska; however, an extensive volcanic gas cloud (sulfur dioxide) and smaller areas of volcanic ash continued to be observed in satellite data over Canada and the Northern Atlantic Ocean through today.
Although the intensity of the eruption has diminished, it is possible for conditions to change at any time and more significant ash emissions may resume with little to no warning. Pauses of days to weeks are common during eruptive episodes at Pavlof. AVO will continue to monitor the volcano closely.
Pavlof Volcano is a snow- and ice-covered stratovolcano located on the southwestern end of the Alaska Peninsula about 953 km (592 mi) southwest of Anchorage. The volcano is about 7 km (4.4 mi) in diameter and has active vents on the north and east sides close to the summit. With over 40 historic eruptions, it is one of the most consistently active volcanoes in the Aleutian arc. Eruptive activity is generally characterized by sporadic Strombolian lava fountaining continuing for a several-month period. Ash plumes as high as 49,000 ft ASL have been generated by past eruptions of Pavlof, and during the 2013 eruption, ash plumes as high as 27,000 feet above sea level extending as much as 500 km (310 mi) beyond the volcano were generated. The nearest community, Cold Bay, is located 60 km (37 miles) to the southwest of Pavlof.
52°49'20" N 169°56'42" W,
Summit Elevation 5676 ft (1730 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW
Moderately elevated surface temperatures were observed in partly cloudy satellite views of the volcano overnight Monday during the past week. No signals of note were detected in seismic or infrasound (pressure sensor) data all week.
Cleveland volcano forms the western portion of Chuginadak Island, a remote and uninhabited island in the east central Aleutians. The volcano is located about 75 km (45 mi) west of the community of Nikolski, and 1500 km (940 mi) southwest of Anchorage. The most recent significant period of eruption began in February, 2001 and produced 3 explosive events that generated ash clouds as high as 39,000 ft above sea level. The 2001 eruption also produced a lava flow and hot avalanche that reached the sea. Since then, Cleveland has been intermittently active producing small lava flows, often followed by explosions that generate small ash clouds generally below 20,000 ft above sea level. These explosions also launch debris onto the slopes of the cone producing hot pyroclastic avalanches and lahars that sometimes reach the coastline.
OTHER ALASKA VOLCANOES
Other Alaska volcanoes show no signs of significant unrest: http://www.avo.alaska.edu/activity/
AVO scientists conduct daily checks of earthquake activity at all seismically-monitored volcanoes, examine web camera and satellite images for evidence of airborne ash and elevated surface temperatures, and consult other monitoring data as needed.
For definitions of Aviation Color Codes and Volcano Alert Levels, see: http://www.avo.alaska.edu/color_codes.php
FOR MORE INFORMATION ON ALASKA VOLCANOES: http://www.avo.alaska.edu
SUBSCRIBE TO VOLCANO ALERT MESSAGES by email: http://volcanoes.usgs.gov/vns/
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Michelle Coombs, Scientist-in-Charge, USGS
firstname.lastname@example.org (907) 786-7497
Jessica Larsen, Acting Coordinating Scientist, UAFGI
email@example.com (907) 322-4085
The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.