The Alaska Volcano Observatory upgraded the alert level at Shishaldin Volcano in the Aleutian Islands on Thursday after observing some unrest at the summit.
AVO scientist Kristi Wallace says the unusual activity at Shishaldin began Wednesday.
“Little bit ago, AVO changed the color code at Shishaldin from green to yellow based on increased temperatures at the summit crater of Shishaldin Volcano as well as increased steaming yesterday,” she says. “Both of those observations were observed via satellite imagery.
Wallace says the observations don’t mean Shishaldin is in imminent danger of eruption. The yellow status just indicates behavior that isn’t normal.
Shishaldin is the highest peak in the Aleutians, rising about 9,400 feet above sea level. It’s located on Unimak Island about 100 miles northeast of Unalaska.
Shishaldin was last elevated to yellow in 2009, when the same kind of activity occurred. Wallace says that anomaly didn’t result in anything more serious.
Historically, though, Shishaldin has been very active:
“It’s erupted approximately 28 times since 1775, so in historic times it’s erupted quite frequently, although the eruptions are typically low-level plumes and ash and steam plumes,” Wallace says. “So [it’s] not a particularly dangerous volcano, although the eruption that occurred in 1999 did send ash plumes as high as 45,000 feet above sea level.”
Wallace says the AVO is going to keep monitoring Shishaldin for signs of explosions. But the seismic stations closest to the summit aren’t working right now. That means using more distant monitoring points as their main sources of data.
“There’s a whole network of stations, so we’re just relying on other stations that are not quite as close to the summit area where we’re seeing the activity,” Wallace says. “Hopefully those will be enough for us to pick up a seismic signal, although this volcano’s not just monitored with a seismic network. We’re still using satellite imagery, and then the infrasound stations which are good at detecting explosion signals.”
There are two other volcanoes in the Aleutians currently on a yellow alert. Those are Cleveland, 175 miles southwest of Unalaska, and Veniaminof, northeast of King Cove.