ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, November 14, 2014, 12:21 PM AKST (Friday, November 14, 2014, 21:21 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 eruption of Pavlof Volcano that began on November 12 continues. It has been characterized by lava fountaining from a vent just north of the summit, flows of rock debris and ash descending the north flank of the volcano, and ash emissions observed in satellite images as a narrow plume that extends for distances of up to 125 miles (200 km) at an altitude of up to 16,000 ft (4.8 km) above sea level.
Over the past day, seismic tremor has remained at a level indicative of continuous eruptive activity. Strongly elevated surface temperatures consistent with lava fountaining continue to be observed in satellite data. Ash emissions are visible in satellite data. Aviation users should refer to the National Weather Service for updated SIGMETs on the ash cloud hazard (http://www.weather.gov/aawu/sigmets). No reports of ash fallout on nearby communities have been reported, and we encourage observers to contact AVO should it occur (https://www.avo.alaska.edu/ashfall/ashreport.php).
Past historical eruptions of Pavlof have been characterized by moderate amounts of ash emission, with ash plumes typically rising as high as 20,000 feet (6.1 km) above sea level, but occasionally higher. Near-vent accumulations of spatter produced by lava fountaining occasionally collapse and form hot rock avalanches that sweep down the flanks of the volcano. These hot rock avalanches run out over ice and snow and generate melt water, which leads to the development of sediment-water mudflows known as lahars. Lahars at Pavlof are capable of inundating the main drainages that head on the volcano, and these include the Leontovich and Cathedral Rivers on the north side of the volcano. At the present level of activity, lahars are not expected to be particularly large or hazardous, but streams on the north flank of the volcano could experience sudden increases in flow if or when eruptive activity intensifies. In past eruptions with a similar level of activity, hot rock avalanches have been limited to the flanks of the volcano and extended up to 2-4 km (1.25-2.5 miles) from the vent. During other Pavlof eruptions, ash fallout has been greatest on the proximal flanks of the volcano, but occasionally trace amounts of ash reach nearby communities, including Cold Bay, Sand Point, Nelson Lagoon, and King Cove.
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.
54°45'19" N 163°58'16" W,
Summit Elevation 9373 ft (2857 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE
Seismicity remains above background levels and elevated crater temperatures were observed in satellite images during periods of clear weather over the past week. It is unclear whether low-level eruptive activity continues, as there is no evidence of ash emissions in satellite images and no observations of ash deposits on the snow near the summit. Web camera images were mostly obscured by clouds.
Shishaldin volcano, located near the center of Unimak Island in the eastern Aleutian Islands, is a spectacular symmetric cone with a base diameter of approximately 16 km (10 mi). A 200-m-wide (660 ft) funnel-shaped summit crater typically emits a steam plume and occasional small amounts of ash. Shishaldin is one of the most active volcanoes in the Aleutian volcanic arc, with at least 54 episodes of unrest including over 24 confirmed eruptions since 1775. Most eruptions are relatively small, although the April-May 1999 event generated an ash column that reached 45,000 ft above sea level.
52°49'20" N 169°56'42" W,
Summit Elevation 5676 ft (1730 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW
Low-level volcanic unrest continues at Cleveland. Seismicity remains low, but vigorous steaming from the summit crater was observed in web camera images over the past week during periods of good weather. Steam emissions like these are routinely observed at Cleveland and do not necessarily indicate an increase in volcanic unrest. Satellite observations were mostly obscured by clouds and steaming over the past 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
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John Power, Scientist-in-Charge, USGS
email@example.com (907) 786-7497
Jeff Freymueller, Coordinating Scientist, UAFGI
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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.