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ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
Friday, May 20, 2016 2:58 PM AKDT (Friday, May 20, 2016 22:58 UTC)


CLEVELAND VOLCANO (VNUM #311240)
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.


PAVLOF VOLCANO (VNUM #312030)
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/

FOLLOW AVO ON FACEBOOK: https://facebook.com/alaska.avo

FOLLOW AVO ON TWITTER: https://twitter.com/alaska.avo

CONTACT INFORMATION:
Michelle Coombs, Scientist-in-Charge, USGS
mcoombs@usgs.gov (907) 786-7497

Mike West, Acting Coordinating Scientist, UAFGI
mewest@alaska.edu (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.
VOLCANO ALERT LEVELS
NORMAL
Volcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.
ADVISORY
Volcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.
WATCH
Volcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway but poses limited hazards.
WARNING
Hazardous eruption is imminent, underway, or suspected.
AVIATION COLOR CODES
GREEN
Volcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.
YELLOW
Volcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.
ORANGE
Volcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway with no or minor volcanic-ash emissions [ash-plume height specified, if possible].
RED
Eruption is imminent with significant emission of volcanic ash into the atmosphere likely OR eruption is underway or suspected with significant emission of volcanic ash into the atmosphere [ash-plume height specified, if possible].
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URL: www.avo.alaska.edu/activity/avoreport.php
Page modified: January 21, 2016 16:41
Contact Information: AVO Web Team

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