Three remote Alaska volcanoes are in various states of eruption, one producing lava and the other two blowing steam and ash. This is happening about 1 week after a M8.2 earthquake shook wide parts of Alaska on July 28, 2021.
So far, none of the small communities near the volcanoes have been affected, Chris Waythomas, a geologist with the Alaska Volcano Observatory, said Thursday.
1. Pavlof Volcano
Webcams on Thursday clearly showed episodic low-level ash emissions from Pavlof Volcano, prompting the observatory to raise the volcano’s threat level from yellow, or exhibiting signs of unrest, to orange, indicating an eruption is underway with minor volcanic ash emissions.
Ash clouds were rising just above the volcano’s 8,261-foot (2,518-meter) summit, drifting about 6 miles (9.7 kilometers) to the south before dissipating, Waythomas said.
Pavlov is a “very sneaky volcano,” Waythomas said. “It can get going without much warning.”
He described the peak as an open system volcano, meaning its “magmatic plumbing system is open and magmas can move to the surface really fast and it can start erupting almost with no warning.”
Pavlov is a snow- and ice-covered stratovolcano on the southwestern end of the Alaska Peninsula, nearly 600 miles (965.6 kilometers) southwest of Anchorage.
The nearest community is Cold Bay, about 35 miles (56.33 kilometers) southwest of Pavlov, which is considered one of Alaska’s most active volcanoes in the Aleutian Islands arc of active and dormant volcanoes.
Pavlov last erupted in 2016, dropping some ash on another community, Nelson Lagoon.
“Unrest continues at Pavlof volcano and minor ash emissions to just above the summit of the volcano were observed this morning. Seismic tremor and small explosions have been detected by local seismic and infrasound instruments.
“The ash emissions observed this morning were limited in extent and likely produced only local fallout on the southeast flank of the volcano. The heightened level of unrest at Pavlof prompted AVO to raise the Aviation Color Code and Volcano Alert Level to ORANGE/WATCH this morning.
“The level of unrest at Pavlof can change quickly and the progression to eruptive activity can occur with little or no warning. AVO continues to monitor Pavlof closely and will provide any new information about the status of the volcano when or if it becomes available.”
2. Great Sitkin volcano
The observatory on Thursday received reports from people in the community of Adak of a lava fountain at the summit of the Great Sitkin volcano. The reports were later confirmed by webcam.
“The fact that they just happen to walk outside and see it was really great,” Waythomas said.
He said if activity increases, Adak could get ashfall from Great Sitkin, located on an island about 27 miles (43.45 kilometers) away.
“This lava fountain is kind of unusual for Great Sitkin, but it’s been fairly passive at this point,” he said.
Great Sitkin, a stratovolcano with a caldera and dome, is about 1,150 miles (1,851 kilometers) southwest of Anchorage.
“Unrest continues at Great Sitkin volcano. Over the past day, numerous earthquakes and small explosions have been recorded on local infrasound and seismic stations. This morning, local observers reported low-level lava fountaining at the active vent that was also visible from Adak Island.
“A robust volcanic cloud has been observed in web camera views of the volcano throughout the day today. This cloud is extending to the north-northeast below about 10,000 feet above sea level. It likely consists mostly of volcanic gas and water vapor but could include some amount of ash.
“Renewed explosive activity or lava effusion remain possible outcomes of the current period of unrest. This is not certain and a decline in unrest to background levels of activity is also possible. Great Sitkin volcano is monitored by local seismic and infrasound sensors, satellite data, web cameras, and remote infrasound and lightning networks.”
3. Semisopochnoi Volcano
Semisopochnoi Volcano, about 150 miles (241 kilometers) away on an uninhabited island at the western end of the Aleutian Islands, has been erupting intermittently and on Wednesday produced an ash cloud that went to about 10,000 feet (3,048 meters) into the air, Waythomas said.
“Unrest continues at Semisopochnoi volcano. Detection of multiple, discrete, energetic explosion signals on local seismic and infrasound stations has characterized the unrest, similar to what has been detected over the past several days.
“Last night another small ash cloud was generated and was visible in satellite data from about 05:23 UTC 8/5/2021 (9:23 PM AKDT, 8/4/2021) until about 10:50 UTC, 8/5/2021 (02:50 AM AKDT). The ash cloud drifted to the southeast over Gareloi and southern Tanaga Island about 180 km before it was no longer visible in GOES-17 data.
“Ash emissions also were visible in web camera views of north crater yesterday evening. Satellite data confirmed that emissions of sulfur dioxide gas were occurring over the past day.
“Small eruptions producing minor ash deposits within the vicinity of the active north crater of Mount Cerberus and ash clouds under 10,000 ft above sea level are typical of recent activity at Semisopochnoi.
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