ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, July 19, 2013, 12:01 PM AKDT (Friday, July 19, 2013, 20:01 UTC)

PAVLOF VOLCANO (VNUM #312030)
55°25'2" N 161°53'37" W, Summit Elevation 8261 ft (2518 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Pavlof was obscured by clouds in satellite data and web camera images during the week. Seismic activity has been low. No ash or gas emissions have been detected in satellite data, web camera images, or reported by pilots. Observers in the field report on-going lava flows and associated water drainage down the north-northwest flank of Pavlof.

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.

VENIAMINOF VOLCANO (VNUM #312070)
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. Available data indicate an ongoing low-level eruption characterized by effusion of lava and emission of minor amounts of ash and steam.

Satellite data continue to 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.

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

Cleveland volcano was obscured by clouds in satellite data throughout the week. No elevated surface temperatures or other outward signs of unrest were observed. AVO has received no other reports of activity at the volcano.

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

CONTACT INFORMATION:

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

Jeff Freymueller, Coordinating Scientist, UAFGI
jeff.freymueller@gi.alaska.edu (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.

---