Alaska Volcano Could Be Getting Ready to Erupt

A volcano near Alaska's largest city is showing new signs of unrest, with experts saying the likelihood of an eruption at Mount Spurr in the next few weeks or months has increased. The Alaska Volcano Observatory said Wednesday that it had measured during recent overflights "significantly elevated volcanic gas emissions," and said signs indicated an eruption of the volcano near Anchorage was likely, though not certain, in the weeks or months ahead. "We expect to see further increases in seismic activity, gas emissions and surface heating prior to an eruption, if one were to occur," the observatory said in a statement. "Such stronger unrest may provide days to weeks of additional warning." More, from the AP:

• What is Mount Spurr? It is an 11,070-foot tall, ice- and snow-covered volcano roughly 80 miles northwest of Anchorage. Mount Spurr is one of 53 volcanoes in Alaska that have been active within the last 250 years. It has two main vents.

• When did Mount Spurr last erupt? The last known eruption from the summit vent was more than 5,000 years ago. The Crater Peak vent, meanwhile, erupted once in 1953 and three times in 1992, according to the observatory. The Crater Peak vent is about 2 miles south of the summit. There have been periods of increased earthquake or other activity since then, including between 2004 and 2006, but no other eruptions. Last October, the observatory raised its alert status for Mount Spurr from green to yellow when an increase in seismic activity became pronounced and a ground deformation was spotted in satellite data. The most likely outcome of the current unrest would be an eruption or eruptions similar to those in 1953 and 1992, the observatory said.
• What impacts could an eruption have? The eruptions during the last century lasted between three and seven hours, produced ash columns that rose more than 50,000 feet above sea level and deposited ashfall in south-central Alaska communities, according to the observatory. In 1992, ashfall of about a quarter-inch in Anchorage prompted residents to stay inside or to wear masks if going outside to avoid breathing ash. The cloud drifted as far as Greenland. The 1992 eruptions prompted the temporary closures of airports in Anchorage and other communities.

Matt Haney, the scientist in charge of the Alaska Volcano Observatory, tells Alaska Public Media that researchers have seen a "checklist" of signs of an impending eruption—an increased number of earthquakes, an increase in gases, the melting of snow, and an inflating surface. He says there's a chance the volcano could erupt with "little or no additional warning," posing a risk to people within 15 to 20 miles. "There would be more proximal hazards, like hot flows of ash and gas called pyroclastic flows that would go down the slopes of the volcano," Haney says. "There can also be volcanic mudflows called lahars." (More volcano stories.)