Last updated at 5:15 p.m. on Wednesday, May 17
Tuesday night, the Alaska Volcano Observatory (AVO) said a pilot reported an eruption of the Bogoslof Volcano that produced an ash cloud that went as high is about 34,000 feet. According to the organization, the eruption began at 10:32 p.m. Tuesday.
In an updated report posted Wednesday morning, AVO said the eruption lasted 73 minutes. According to the organization, the ash cloud moved southwest, “along the edge of a mass of weather clouds as seen in satellite images.”
“If we think it may have another explosive event, if seismicity is still high we might keep it at Red for a while, but it had dropped down to lower levels and it was essentially at background levels, so we wanted to reduce it down to orange,” said Hans Schwaiger, Geophysicist with the AVO.
Bogoslof has been active with multiple eruptions since December, but had a two month gap in explosive activity until Tuesday night. Schwaiger says the recent eruption was one of the largest in this sequence.
The volcano is providing new opportunities for research.
“It’s different from most of the other volcanoes we deal with because it comes through the ocean, and so there’s a different character to the plumes, there’s more lightning detection we’re getting off these so it’s an interesting science study as well,” said Schwaiger.
Bogoslof’s eruption wasn’t the only in the Aleutians Tuesday night.
Cleveland Volcano erupted three hours earlier, just after 7:30 p.m. The eruption only lasted about 10 minutes, but sent an ash cloud to about 15,000 feet. The Alaska Volcano Observatory says the dome at the summit was completely removed by this explosion.
The ash cloud could be seen on satellite data drifting southwest of the volcano for about 5 hours.
Original story posted on Tuesday, May 16
Bogoslof Volcano — the largest volcano in a cluster of small, low-lying volcanos off the coast of Alaska’s Aleutian Islands — “remains at a heightened state of unrest and in an unpredictable condition,” according to a Tuesday report from the Alaska Volcano Observatory (AVO). But in the update, the organization said no volcano activity had been recorded over the last day.
Over the winter, the island saw continued activity. And in the Tuesday post, AVO said volcanic activity could ramp up, producing explosions and volcanic clouds at an altitude of 15,000 feet, without much of a precursor.
“Some previous explosions have been preceded by an increase in earthquake activity that allowed for short-term forecasts of imminent significant explosive activity,” AVO explained. “Although, we are able to detect energetic explosive activity in real-time, there is typically a lag of tens of minutes until we can characterize the magnitude of the event and the altitude of the volcanic cloud. It is possible for low-level unrest, including explosive activity, to occur that we are unable to detect with existing data sources. Such low-level periods of unrest and possible explosions could pose a hazard in the immediate vicinity of the volcano.”
The last major explosive event on the island was March 8, the organization said.
On May 8, AVO geoscientist Max Kaufman traveled to the area with the U.S. Coast Guard and captured the volcano in a series of misty, Bering Sea photos. In a Facebook post, AVO wrote, “Bogoslof Island has a new lava dome formed during the 2016-2017 eruption on the north side of the island, and a steaming center lake.”
AVO says they don’t have any volcanic monitoring equipment, ground based, on Bogoslof. They’re monitoring it by using satellite images, information from the Worldwide Lightning Location Network, and data from infrasound instruments on nearby islands for any sign of volcanic activity.