Volcano Update from Archive



ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
Friday, May 24, 2013 11:38 AM AKDT (Friday, May 24, 2013 19:38 UTC)


PAVLOF VOLCANO (CAVW #1102-03-)
55°25'2" N 161°53'37" W, Summit Elevation 8261 ft (2518 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

The eruption of Pavlof continues, but at a lower level of activity than earlier in the week. Early in the week, continuous seismic tremor, intense elevated surface temperatures, and ash, gas and steam emissions characterized activity. A continuous plume of steam, ash, and gas, occasionally reaching up to 22,000 ft. above sea level but mostly below 15,000 ft., was observed in satellite images, by pilots, and observers on the ground in Cold Bay and Sand Point. Trace amounts of ash fall occurred in the community of Sand Point on May 18 and Nelson Lagoon on May 19-21. A lava flow advanced down the northwest flank, and lava fountaining was observed at the vent. Seismic tremor declined markedly on Wednesday morning and was replaced by small discrete explosions. The numbers and amplitude of these explosions have varied over the past several days. Cloudy conditions since Monday have hampered direct observation of the vent and ash plume but a pilot report and photos from Wednesday morning showed a very weak steam and gas plume with little to no ash issuing from the vent. Over the past day, distinct small explosion signals were detected on seismic instruments and pressure sensors and weak ash signal was detected in satellite images indicating that these small explosions contain minor amounts of ash at times.

During past eruptions of Pavlof, the style of eruptive activity fluctuated from higher to lower levels. Therefore, this apparent lower-level activity does not necessarily indicate that the eruption is ending. Although the activity to date has been characterized by relatively low-energy lava fountaining and ash emission, more energetic explosions could occur without warning that could place ash clouds above 20,000 ft. Depending on wind direction and strength, trace to minor ash fall may occur on local communities downwind. Information about mitigating the effects of volcanic ash can be found on the AVO web page.

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.

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

Elevated surface temperatures were observed in satellite images over the past week indicative of ongoing low-level activity. AVO has received no reports of ash emission or other indications of eruptive activity over the past 24 hours.

Sudden explosions of blocks and ash are possible with little or no warning. 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 quickly. However, for some events, a delay of several hours is possible. 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, Veniaminof, 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.