ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, July 12, 2013, 11:24 AM AKDT (Friday, July 12, 2013, 19:24 UTC)
55°25'2" N 161°53'37" W,
Summit Elevation 8261 ft (2518 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW
There has been no evidence of eruptive activity at Pavlof over the past week. Seismic activity remains very low. Mostly cloudy satellite observations over the past week showed no unusual activity. No ash or gas emissions have been detected in satellite data, web camera images, or reported by pilots.
During earlier periods of the current eruption and past eruptions of Pavlof, the style of eruptive activity has fluctuated from higher to lower levels. Such a fluctuation occurred during the current eruption on May 28, when eruptive activity paused until resuming on June 4. Therefore, the current pause in eruptive activity does not necessarily indicate that the eruption has ended. Renewed activity is possible, and may not be preceded by significant seismic activity. AVO will continue to monitor Pavlof closely.
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
Nearly continuous, low-level volcanic tremor has 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. Web camera images of the volcano from Perryville throughout the past week showed small emissions of gas and ash, which were confined to the caldera area. Some nighttime images showed incandescence of the intracaldera cone. These data indicate an ongoing low-level eruption characterized by effusion of lava and emission of minor amounts of ash and steam.
Satellite data obtained this week indicates that most of the active lava flows extend a short distance (a few thousand feet) south of 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. Geologic studies indicate that flowage events toward Perryville are highly unlikely.
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. The lava flow may continue to grow slowly and is not expected to lead to any significant hydrologic events in the drainages north of the volcano associated with melting of snow and ice.
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
Jeff Freymueller, Coordinating Scientist, UAFGI
email@example.com (907) 378-7556
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.