ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, June 19, 2015, 1:34 PM AKDT (Friday, June 19, 2015, 21:34 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, with minor ash emissions observed over the past day and continuing. Yesterday, pilot reports and a satellite image indicated a weak ash plume rising a few hundred feet from the summit crater, and ash deposits on the volcano's upper flanks. Today, clear webcam views show that weak ash emissions continue.

Elevated surface temperatures were detected in satellite images during the week. Seismicity remains above background levels and is characterized by continuous seismic tremor. Throughout the week, tremor levels have remained fairly consistent despite the recent slight uptick in eruptive activity.

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.

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

Renewed unrest was detected at Cleveland over the past week. Elevated surface temperatures were detected in satellite images throughout the week, and a dusting of light ash was observed near the summit on Sunday, June 14. The view from the webcam was clear intermittently throughout the week, and showed light steaming. The consistently elevated temperatures are consistent with possible renewed growth of the small lava dome that sits in the summit crater of the volcano.

No significant activity was detected in seismic or infrasound (air pressure) data.

The increase in heat output, and possible growth of the dome, suggests that new magma is slowly ascending to the surface. The possibility of ash-producing explosions has thus increased. Most such explosions do not send ash higher than 20,000 feet above sea level, but larger explosions are possible.

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

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:

Dave Schneider, Acting Scientist-in-Charge, USGS
djschneider@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.

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