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ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, May 20, 2016, 2:58 PM AKDT (Friday, May 20, 2016, 22:58 UTC)
52°49'20" N 169°56'42" W,
Summit Elevation 5676 ft (1730 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE
A small-volume lava dome was extruded from the vent in the summit crater of Cleveland Volcano earlier this week (May 17 or 18). The low-relief 50-meter (165 ft) diameter dome is similar in size and shape to the ten domes observed since 2011, the most recent of which was extruded and destroyed earlier this month. Seismicity remains low and no explosions have been detected in infrasound (pressure sensor) or satellite data over the past week.
Previous domes have been destroyed by short duration explosive events that shower the upper cone with large blocks of lava, produce debris flows down the flanks of the volcano that at times extend to the ocean, and generate small volume ash clouds that are typically too small to be be observed in meteorological satellite data with coarse spatial resolution. These explosions happen without warning, but are usually detected by pressure sensor data on the island, and/or at more distant locations.
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 or domes, 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.
55°25'2" N 161°53'37" W,
Summit Elevation 8261 ft (2518 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW
The recent period of eruptive activity at Pavlof Volcano that began on May 13, 2016 has ended and the Aviation color code and Volcano Alert Level were reduced to YELLOW/ADVISORY earlier today. Four minor ash eruptive episodes were inferred from seismic data over the past week, the last of which occurred on May 16. Since then, we have not detected seismic signals associated with ash emissions. The volcanic ash clouds produced during this recent period of activity were low (below 4.5 km or 15,000 ft above sea level, too small to be observed in satellite data), and quickly dissipated. No lava effusion or fountaining was detected or observed during this eruption.
The volcano remains in a heightened state of unrest. Pauses in eruptive activity of days to weeks are common during eruptive episodes of Pavlof Volcano. A return to eruptive activity remains possible and could occur with little or no warning. Thus, AVO will continue to monitor the volcano closely and will issue additional information as necessary.
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 March 2016 eruption, ash plumes as high as 40,000 feet above sea level were generated and the ash was tracked in satellite data as distant as eastern Canada. The nearest community, Cold Bay, is located 60 km (37 miles) to the southwest of Pavlof.
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
Mike West, 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.