ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, June 27, 2014, 3:07 PM AKDT (Friday, June 27, 2014, 23:07 UTC)

SHISHALDIN VOLCANO (VNUM #311360)
54°45'19" N 163°58'16" W, Summit Elevation 9373 ft (2857 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

Low-level eruptive activity continues. Consistently elevated temperatures at the summit of Shishaldin Volcano were recorded in satellite images this past week. No significant seismicity was noted. In web camera images, a steam and gas plume was intermittently visible rising from the summit and drifting downwind.

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 small summit crater typically emits a noticeable steam plume with 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 of Shishaldin's eruptions have produced small ash and steam plumes, although a recent eruption in April-May 1999 generated an ash column that reached a height of 45,000 ft above sea level.

SEMISOPOCHNOI VOLCANO (VNUM #311060)
51°55'44" N 179°35'52" E, Summit Elevation 2625 ft (800 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

The Semispochnoi earthquake swarm that began on June 9 continues. The M7.9 earthquake that occurred near the volcano on June 23 appears to have had no impact on the ongoing swarm. No eruptive activity is occurring at Semisopochnoi. Satellite images of the volcano have been mostly cloudy for the past week and AVO has received no reports from pilots or mariners of any unusual activity at Semisopochnoi.

An earthquake swarm is a series of relatively small earthquakes that occur near each other and closely spaced in time. An earthquake swarm beneath a volcano typically means that magma is moving towards the surface, but an earthquake swarm does not always lead to an eruption. AVO continues to track seismic and other monitoring data closely to watch for any acceleration in activity that could indicate an increased likelihood of eruption.

Remote Semisopochnoi ("Seven Peaks") volcano occupies the largest, young volcanic island in the western Aleutians. The volcano is dominated by an 8-km (5-mile) diameter caldera that contains a small lake and a number of post-caldera cones and craters. The age of the caldera is not known with certainty but is likely early Holocene. The last known eruption of Semisopochnoi occurred in 1987, probably from Sugarloaf Peak on the south coast of the island, but details are lacking. Another prominent, young post-caldera landform is Mount Cerberus, a three-peaked cone cluster in the southwest part of the caldera. The island is uninhabited and part of the Alaska Maritime National Wildlife Refuge. It is located 65 km (40 mi) northeast of Amchitka Island and 200 km (130 mi) west of Adak.


CLEVELAND VOLCANO (VNUM #311240)
52°49'20" N 169°56'42" W, Summit Elevation 5676 ft (1730 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

No significant activity was observed in mostly cloudy satellite images over the past week.

Cleveland volcano forms the western half 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 within its summit crater. These extrusive episodes are typically followed by explosions that destroy the lava flow, generate small ash clouds generally below 20,000 ft ASL, and launch debris onto the upper slopes of the volcanic cone.

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

Eruptive activity has ceased at Pavlof. Earlier this week, AVO returned to Aviation Color Code Yellow and Volcano Alert Level Advisory. Small, discrete seismic events continue, however, and eruptive activity could resume at any time with little or no warning.

A very small ash burst, perhaps from collapse of hot material high on the volcano's flanks, was captured in web camera images on June 24. Weakly elevated temperatures in the vicinity of the newly erupted lava flows on the northwest flank were recorded in satellite images throughout the week. No evidence of ash or lava emission from the main vent has been seen since early to mid-June.

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.

VENIAMINOF VOLCANO (VNUM #312070)
56°11'52" N 159°23'35" W, Summit Elevation 8225 ft (2507 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

No activity was observed in partly to mostly cloudy satellite images and web camera views of Veniaminof in the past week. Seismicity remains above background. A steam plume from the intracaldera cone was occasionally visible in Perryville web camera images during clear conditions.

Mount Veniaminof volcano is an andesitic stratovolcano with an ice-filled 10-km diameter summit caldera located on the Alaska Peninsula, 775 km (480 mi) southwest of Anchorage and 35 km (22 mi) north of Perryville. Veniaminof is one of the largest (~ 300 cubic km; 77 cubic mi) and most active volcanic centers in the Aleutian Arc and has erupted at least 13 times in the past 200 years. Recent significant eruptions of the volcano occurred in 1993-95 and 2005. Both were Strombolian eruptions producing lava fountans and minor emissions of ash and gas from the main intracaldera cone. During the 1993-95 activity, a small lava flow was extruded into the ice field producing a melt pit. Minor ash-producing explosions occurred nearly annually between 2002 and 2008. Previous historical eruptions have produced ash plumes that reached 20,000 ft above sea level (1939 and 1956) and ash fallout that blanketed areas within about 40 km (25 mi) of the volcano (1939).


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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CONTACT INFORMATION:

John Power, Scientist-in-Charge, USGS
chris@usgs.gov (907) 786-7497

Jeff Freymueller, Coordinating Scientist, UAFGI
jeff.freymueller@gi.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.

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