ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, June 28, 2013, 12:48 PM AKDT (Friday, June 28, 2013, 20:48 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
Eruptive activity at Pavlof Volcano is continuing, but at a much lower level than earlier this week. Relatively continuous low-level tremor and occasional small explosions have characterized the seismicity for the past several days, and persistent thermal signals also have been observed in satellite data. The thermal features and level of seismic activity are consistent with intermittent, minor episodes of ash emission and lava fountaining.
Beginning late Monday evening and continuing through Wednesday this week, Pavlof experienced an episode of elevated eruptive activity characterized by vigorous lava fountaining and ash emission that was associated with some of the highest levels of seismicity yet recorded during the 2013 eruption. Several ash and vapor plumes rising to 26,000 to 28,000 feet above sea level were observed by pilots and detected in satellite data. On June 25 and 26, sulfur dioxide gas emissions were large enough to be detected in satellite data that indicated a narrow gas plume extending north and south of the volcano for several hundred miles. Sulfur odors were reported by passing pilots. Trace amounts of ash fall were reported in King Cove on June 25. Activity has gradually declined since early Wednesday morning and the volcano has been relatively quiet since then.
At the current level of unrest, some lava fountaining and ash emission may be occurring, but overall, the volcano is relatively quiet. It is possible for conditions to change at any time and more vigorous seismicity and ash emissions may result. Pavlof Volcano often experiences fluctuating levels of eruptive activity and lengthy periods of low-level activity lasting for weeks or more may be punctuated by periods of vigorous lava fountaining and ash emission. Typically, the build up to such activity is gradual and would be identified during routine analysis of seismic, satellite and other monitoring data.
Pavlof volcano is located on the southwestern end of the Alaska Peninsula. Pavlof is a stratovolcano which rises to an elevation of 8262 feet. With almost 40 historic eruptions, it is one of the most consistently active volcanos in the Aleutian arc. Eruptive activity is generally characterized by sporadic strombolian fountaining continuing for a several-month period. The community of Cold Bay is located 60 km (37 miles) to the southwest of Pavlof.
56°11'52" N 159°23'35" W,
Summit Elevation 8225 ft (2507 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE
Volcanic tremor and small explosions have been detected in seismic data throughout the past week and satellite observations continue to show elevated surface temperatures at the intracaldera cone of Veniaminof Volcano. These data indicate an ongoing eruption characterized by effusion of lava and emission of minor amounts of ash and steam. Web camera images from Perryville throughout the past week have shown a small light-colored plume rising above the intracaldera cone to just above the rim of the caldera to about 8,000 to 10,000 feet above sea level. A persistent incandescent glow at the cone has been evident in night time web camera images when not obscured by clouds and fog.
Satellite data obtained this week indicates that a multi-lobed lava flow extends a short distance (a few thousand feet) beyond the intracaldera cone onto the ice and snow within the Veniaminof caldera. AVO has received no reports of unusual hydrologic phenomena in the drainage to the north of the intracaldera cone that might result from the release of meltwater generated by the lava flows flowing over snow and ice.
It remains possible for activity at Veniaminof Volcano to increase above its current level at any time and more vigorous ash emissions may occur. Sustained periods of volcanic tremor may correspond with episodes of continuous ash emission which may not be detected in satellite data, especially if ash plumes remain below 15,000 to 20,000 feet above sea level. Brief bursts of ash emission and small explosions may result in ash fall on the flanks of the volcano, and this is likely to occur while the volcano is at its current level of unrest. A vigorous explosive episode that produces a large ash cloud is not expected at the level of unrest that has been occurring over the past several weeks; however, this remains a possible, but not certain outcome of the present eruption.
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 km3) 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 moderate Strombolian eruptions producing intermittent low-level jets of incandescent lava fragments, and low-level emissions of steam and ash from the main intracaldera cone. During the 1993-95 activity, a small lava flow was extruded into the summit caldera ice field producing an ice pit. Minor ash-producing explosions occurred in 2002, 2004, early 2005, November 2006, and February 2008. Previous historical eruptions have produced ash plumes that reached 6,000 m (20,000 ft) above sea level and ash fallout that blanketed areas within about 40 km (25 mi) of the volcano.
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 elevated surface temperatures or other outward signs of unrest were observed in satellite images over the past week. AVO has received no other reports of activity at the volcano.
Sudden explosions of blocks and ash are possible with little or no warning and ash clouds, if produced, could exceed 20,000 feet above sea level. If a large ash-producing event occurs, nearby seismic, infrasound, or volcanic lightning networks should alert AVO staff. However, for some events, detection may not be possible for several hours. Cleveland volcano does not have a local seismic network and is monitored using only distant seismic and infrasound instruments and satellite data.
Cleveland volcano forms the western half of Chuginadak Island, a remote and uninhabited island in the east central Aleutians. It is located about 75 km (45 mi.) west of the community of Nikolski, and 1500 km (940 mi.) southwest of Anchorage. The volcano's most recent significant eruption began in February, 2001 and it produced 3 explosive events that produced ash clouds as high as 12 km (39,000 ft) above sea level. The 2001 eruption also produced a rubbly lava flow and hot avalanche that reached the sea. The most recent minor ash emissions were observed in November 2012.
OTHER ALASKA VOLCANOES
Seismic activity is monitored in real time at 29 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. Akutan, Aniakchak, Augustine, Dutton, Fisher, Fourpeaked, Gareloi, Great Sitkin, Griggs, Iliamna, Isanotski, Kanaga, Katmai, Mageik, Makushin, Martin, Novarupta, Okmok, Redoubt, Shishaldin, Snowy, Spurr, Tanaga, Trident, Ugashik-Peulik, Ukinrek Maars, and Westdahl 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 of these volcanoes.
Please see http://www.avo.alaska.edu/color_codes.php
for complete definitions of Aviation color codes and Volcano alert levels.
VOLCANO INFORMATION ON THE INTERNET: http://www.avo.alaska.edu
RECORDING ON THE STATUS OF ALASKA'S VOLCANOES (907) 786-7478
John Power, Scientist-in-Charge, USGS
firstname.lastname@example.org (907) 786-7497
Janet Schaefer, Acting Coordinating Scientist,
Alaska Division of Geological and Geophysical Surveys
email@example.com (907) 451-5005
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.