ANCHORAGE, Alaska – A sulfurous steam plume, hundreds of miniature earthquakes and a new swath of ash on snowy Augustine Volcano have scientists looking for 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 Wednesday.
The observatory has been monitoring the uninhabited 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.
"On Sunday night I woke up with the taste of sulfur in the back of my throat," said Kevin Seville, who lives in the Russian and Alutiiq village of Nanwalek.
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 magnitudes — less than 1 — were still smaller than the bulk of the earthquakes preceding the 1986 eruption.
The entire island, located 171 miles southwest of Anchorage, has inflated by as much as one inch as injections of molten rock rise into the mountain from beneath the earth's surface, he 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.
"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.
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.