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ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
Friday, July 18, 2008 11:43 AM AKDT (Friday, July 18, 2008 19:43 UTC)


OKMOK VOLCANO (CAVW #1101-29-)
53°23'49" N 168°9'58" W, Summit Elevation 3520 ft (1073 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

The 2008 eruption of Okmok Volcano, which began on July 12 at 11:43 AKDT (19:43 UTC), continues. The initial phase of the eruption was quite explosive and produced a wet, ash and gas-rich plume that reached 50,000 feet above sea level. Wet, coarse (sand-sized) ash fall was reported within minutes of the eruption's start at Fort Glenn, about 10 km E/SE of Okmok Caldera. A light ashfall was also reported at Unalaska/Dutch Harbor by 13:00 AKDT. Based on pilot reports, airborne photographs, and radar intensity images, the eruptive vent appears to be new, having formed to the northwest of Cone D (located east of the center of the caldera).

Over the last week, the severity of eruption has slowly declined. Pilot reports, seismicity, and satellite data all indicate that the eruption is now episodic, with occasional, ash-producing explosions occurring every 15 to 30 minutes. The plumes from these explosions appear to be limited to about 20,000 feet above sea level.

The current Okmok eruption differs from eruptions of the recent past in two important respects: it has been considerably more explosive, and it has occurred in a different place. Prior to this eruption, and at least since the late 1800s, eruptive activity had been concentrated at Cone A, in the southwestern corner of the caldera, and had been limited to relatively low-level plumes, generally less than 30,000 feet above sea level. Because of these differences, it is not a simple matter to forecast the eventual course of the current eruption based on recent past experience. Over the next several weeks to months, intermittent explosions are likely to occur, and some of these may produce ash plumes to 30,000 feet above sea level. Lava fountaining and lava flows are also possible, although these will result in hazards confined mainly within the caldera. We also cannot rule out a return to more vigorous explosions, perhaps even exceeding the size of those on July 12.

Please see http://www.avo.alaska.edu/activity/Okmok.php for more information.

CLEVELAND VOLCANO (CAVW #1101-24-)
52°49'20" N 169°56'42" W, Summit Elevation 5676 ft (1730 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Satellite and webcam views were mostly cloudy this week, though on July 14 and today thermal anomalies were visible at Cleveland's summit. AVO received no other reports of activity at Cleveland this week.

AVO monitors Cleveland Volcano with satellite imagery as weather allows. The lack of a real-time seismic network at Cleveland means that AVO is unable to track local earthquake activity related to volcanic unrest. Short-lived explosions of ash that could exceed 20,000 ft above sea level can occur without warning and may go undetected on satellite imagery. Please see http://www.avo.alaska.edu/activity/Cleveland.php for more information.

OTHER ALASKA VOLCANOES

Seismic activity is monitored in real time at 31 volcanoes in Alaska. Satellite images of all Alaskan volcanoes are analyzed daily for evidence of ash plumes and elevated surface temperatures. Some volcanoes may currently display anomalous behavior but are not considered to be at a dangerous level of unrest. Wrangell, Spurr, Redoubt, Iliamna, Augustine, Fourpeaked, Snowy, Katmai, Griggs, Trident, Novarupta, Mageik, Martin, Ugashik-Peulik, Ukinrek Maars, Aniakchak, Veniaminof, Pavlof, Dutton, Isanotski, Shishaldin, Fisher, Westdahl, Akutan, Makushin, Korovin, Great Sitkin, Kanaga, Tanaga, and Gareloi volcanoes are in color code GREEN and volcano alert level Normal. All are at or near normal levels of background seismicity. AVO did not detect ash plumes or significant elevated surface temperatures in the vicinity of any volcano.

Please see http://www.avo.alaska.edu/color_codes.php for complete definitions of Aviation color codes and Volcanic activity alert levels.

VOLCANO INFORMATION ON THE INTERNET: http://www.avo.alaska.edu
RECORDING ON THE STATUS OF ALASKA'S VOLCANOES (907) 786-7478

CONTACT INFORMATION:
John Power, Acting Scientist-in-Charge, USGS
jpower@usgs.gov, (907)786-7497

Steve McNutt, Coordinating Scientist, UAFGI
steve@giseis.alaska.edu (907)978-5458

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].
Contact AVO Privacy Accessibility Information Quality FOIA
URL: avo.alaska.edu/activity/avoreport.php
Page modified: May 16, 2014 09:40
Contact Information: AVO Web Team

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