Alaska’s Augustine Volcano Showing Signs of Erupting, Scientists Say

A sulfurous steam plume, hundreds of miniature earthquakes and a new swath of ash on Alaska’s snowy Augustine Volcano have scientists alerted to a possible eruption in the next few months.

The 4,134-foot volcano hasn’t shown such signs since it last erupted in 1986, when ash from a 7-mile-high column drifted over Anchorage, the state’s most populous city, and kept flights out of the skies over Cook Inlet.

“It’s steaming more vigorously right now than it has at any point since 1986,” Steve McNutt, research professor of volcano seismology with the Alaska Volcano Observatory, said.

The observatory has been monitoring the volcanic island more closely since bumping its status up to code yellow from green on Nov. 29. Code yellow means the volcano is restless and showing signs of an eruption.

Steam mixed with sulfur dioxide gas has been billowing vigorously since late last week from a space between lava domes formed during Augustine’s most recent eruptions, in 1976 and 1986.

The presence of sulfur, one of the main magmatic gases, is a sign that molten rock has moved closer to surface, McNutt said.

Residents on the Kenai Peninsula about 50 miles across Cook Inlet have reported the rotten-egg smell of sulfur fumes floating into their communities over the last few days.

“On Sunday night I woke up with the taste of sulfur in the back of my throat,” Kevin Seville, who lives in the Russian and Alutiiq village of Nanwalek, said.

The number of earthquakes on Augustine, on the eastern end of the Aleutian volcanic arc, has increased tremendously in the past week.

Seismometers have recorded more than 170 small temblors over the last week, and 74 on Sunday alone. The average for the past 15 years has been about one to two per week.

The jump is “very dramatic,” McNutt said. But he noted the low magnitudes — less than 1 — were still smaller than the bulk of the earthquakes preceding the 1986 eruption.

He said the entire island has inflated by as much as one inch as injections of molten rock rise into the mountain from beneath the earth’s surface.

“You could picture it as a balloon expanding under a pile of sand,” McNutt said.

Scientists on a flyover earlier this week also spotted a swath of new ash on the snow-covered peak. The thin dusting indicates cracks have opened on the mountain to vent steam.

The uninhabited volcanic island has a history of long periods of activity leading up to an eruption.

“It could be days, weeks, months before we see something else, or at any point here things could just stop,” said Chris Nye, research assistant professor at the observatory, a joint program between the U.S. Geological Survey, University of Alaska Fairbanks and state Division of Geological and Geophysical Surveys.

The last time Augustine erupted, ash filled the skies over Anchorage, 171 miles to the northeast, and disrupted air and mail service at the city’s airport, the largest in the state.

Nanwalek residents are monitoring the volcano observatory’s Web site and have packed emergency supplies in case an ash cloud cuts out air service, the main source of transportation to and from the village.

“We’re isolated as it is, when you throw ash into the mix, it makes it really hard to connect,” Seville said.

Nanwalek and other Kenai Peninsula communities are constantly wary of the volcano.

“You can’t miss it on a clear day. It’s just a big mountain,” Seville said. “Sometimes it looks like you can reach out and just grab it.”

Augustine is a stratovolcano, composed of alternating layers of
lava and ash, on the eastern boundary of the 2,500-mile Aleutian
chain. Aleutian volcanoes are formed as the Pacific plate burrows
under the North American plate.

Topics Catastrophe Natural Disasters Alaska