ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, August 23, 2013, 12:08 PM AKDT (Friday, August 23, 2013, 20:08 UTC)
56°11'52" N 159°23'35" W,
Summit Elevation 8225 ft (2507 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE
Seismicity associated with the ongoing eruption of Veniaminof Volcano has gradually declined over the past week. Earlier in the week, the eruption was characterized by relatively high levels of nearly continuous, gradually fluctuating tremor that corresponded with steady effusion of lava from two vents on the intracaldera cone. This activity also was accompanied by brief bursts of ash that produced low-level ash plumes rising to about 12,000 feet above sea level. Over the past 48 hours, the character of the seismicity has changed to more discreet earthquake activity and short bursts of tremor that probably correspond with brief periods of ash emission. When the volcano is not obscured by clouds, low-level (<12,000 feet above sea level) diffuse ash plumes have been observed in the FAA web camera in Perryville, and prominent, sometimes intense thermal signals have been evident in satellite data. During the week, AVO received several reports of rumbling noises and explosions (some of them felt) by residents of Perryville, and trace ash fall also was reported in Perryville on August 20. On Sunday, August 18, scientists from Dickinson College and AVO visited the volcano and made observations of the lava flows and ash emissions. These observations and a synopsis of the eruption to date were described in an Information Statement released by AVO on August 21 (http://www.avo.alaska.edu/activity/Veniaminof.php).
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 anomalous activity at Cleveland Volcano was observed in satellite imagery during the past week. The last confirmed episode of unrest, confirmed by observations of elevated surface temperatures and a plume, occurred about three weeks ago, in late July. A report from a USGS scientist who visited the volcano on July 30 indicates nothing unusual was occurring. AVO has received no other reports of activity at the volcano throughout the week.
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, Pavlof, 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
David Fee, Acting Coordinating Scientist, UAFGI
email@example.com (907) 474-7564
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.