Pavlof Volcano continues to erupt from the east vent near the volcano’s summit. Seismic tremor and elevated surface temperatures are consistent with low-level eruption and effusion of short lava flows on the upper flank. No explosions or ash emissions were observed in satellite or webcam images this week. 
 
Periods of lava spatter and fountaining from the vent on the volcano’s upper east flank have been occurring since mid-November 2021. This activity has built a small cone and sent flows down the flank that melt the snow and ice and produce variable amounts of meltwater. The meltwater typically incorporates loose debris on the flank of the volcano and forms thin (less than 2 m thick) lahars. The lahar deposits extend down the east-southeast flank for several kilometers, not quite to the base of the volcano. 
 
Previous eruptions of Pavlof indicate that the level of unrest can change quickly and the progression to more significant eruptive activity can occur with little or no warning. 
 
Pavlof is monitored by local seismic and infrasound sensors, satellite data, web cameras, and remote infrasound and lightning networks. 

Slow lava effusion from the summit crater of Great Sitkin Volcano continued this week, as observed in a satellite radar image from May 11.  Elevated surface temperatures were detected throughout the past week which is consistent with continued lava effusion. Seismic activity remains low.  
 
The terrain is steep near the terminus of the lava flow lobes, and blocks of lava could detach without warning and form small rock avalanches in these valleys. These avalanches may liberate ash and gas and could travel several hundred meters beyond the lava flows; they would be hazardous to anyone in those areas.  
 
Great Sitkin is monitored by local seismic and infrasound sensors, satellite data, web cameras, and remote infrasound and lightning networks. 

The eruption at Semisopochnoi volcano continued throughout the past week. Seismicity remained elevated with ongoing periods of seismic tremor. Multiple explosions were detected in seismic and infrasound data on all but one day this week.  Clear satellite and web camera views most of the week showed low-level ash emissions. 
 
Small explosions have characterized the recent activity and show no signs of abating. These produce minor ash deposits within the vicinity of the active north crater of Mount Cerberus, with ash clouds typically lower than 10,000 ft (3 km) above sea level. 
 
Semisopochnoi is monitored by local seismic and infrasound sensors, satellite data, web cameras, and remote infrasound and lightning networks. 

Elevated surface temperatures have been observed at Cleveland in clear satellite views since May 4, and elevated sulfur dioxide emissions were observed in satellite data May 8-11. Based on these observations, AVO increased the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY on May 11.  No other signs of unrest have been detected. 

 
Episodes of lava effusion and explosions can occur at Cleveland without advance warning. Explosions are normally short duration and only present a hazard to aviation in the immediate vicinity of the volcano. Larger explosions that present a more widespread hazard to aviation are possible but are less likely and occur less frequently. 
 
Cleveland volcano is monitored by only two seismic stations, which restricts AVO's ability to precisely locate earthquakes and detect precursory unrest that may lead to an explosive eruption. Rapid detection of an ash-producing eruption may be possible using a combination of seismic, infrasound, lightning, and satellite data. 

Strong northwesterly winds in the vicinity of Katmai and the Valley of Ten Thousand Smokes have picked up loose volcanic ash erupted during the 1912 Novarupta-Katmai eruption and carried it to the southeast toward Kodiak Island today (May 13). The National Weather Service has issued a SIGMET for this low-level event and suggests that the maximum cloud height is 6,000 ft above sea level. 
 
This phenomenon is not the result of recent volcanic activity and occurs seasonally in the spring and fall during times of high winds and dry snow-free conditions in the Katmai area and other young volcanic areas of Alaska. All of the volcanoes of the Katmai area (Snowy, Griggs, Katmai, Novarupta, Trident, Mageik, Martin) remain at color code GREEN. 
 
Resuspended volcanic ash should be considered hazardous and could be damaging to aircraft and health. For more information on volcanic ash and human health, visit the following website: http://volcanoes.usgs.gov/ash/. Official warnings about these ash resuspension events are issued by the National Weather Service: http://www.weather.gov/afc. Forecasts of airborne ash hazard to aircraft: http://www.weather.gov/aawu . Volcanic Ash Advisories: http://vaac.arh.noaa.gov/ . Forecasts of ash fall: http://www.weather.gov/afc. Air quality hazards and guidance from Alaska Department of Environmental Conservation, Division of Air Quality: http://dec.alaska.gov/Applications/Air/airtoolsweb/Advisories/Index