ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, June 13, 2014, 2:59 PM AKDT (Friday, June 13, 2014, 22:59 UTC)

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

A swarm of earthquakes at Semisopochnoi volcano started at 10:00 AKDT (18:00 UTC) on June 9 and escalated June 12, at approximately 12:00 AKDT (20:00 UTC). The anomalous seismic activity has continued, prompting AVO to raise the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY. No eruptive activity is currently indicated.

AVO is closely monitoring the situation and will issue further updates as conditions change.

Semisopochnoi volcano is monitored by a 6-station seismic network as well as satellite imagery. Five of the seismic stations on Semisopochnoi are currently operational. The telemetry system for the Semisopochnoi stations, located on Amchitka Island, was just repaired in late May.

Remote Semisopochnoi 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.

PAVLOF VOLCANO (VNUM #312030)
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 continued over the past week. Seismic activity has been steady during the week and been characterized by intermittent seismic events. Weakly elevated surface temperatures were observed occasionally in mostly cloudy satellite images. Observations indicated lava fountaining continued at the active vent, although ash production was insignificant. Nothing was observed in mostly cloudy web camera views all week.

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.

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 continued at Shishaldin during the past week. Weakly elevated surface temperatures were observed on one day of the week in satellite images, under mostly cloudy conditions. Web camera views of the volcano have been obscured by weather. No significant seismicity has been observed over the past week.

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.

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 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 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.

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

Seismicity has remained slightly above background during the past week. No significant activity was observed in cloudy satellite images and web camera views.

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:

Chris Waythomas, Acting 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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