The likelihood of an Alaska volcano’s explosive eruption not far from the state’s largest city has increased, according to researchers.
Scientists like Matt Haney have had their eyes on Mount Spurr for months.
“It started almost a year ago, with increased amounts of earthquakes beneath a volcano, and we've been tracking that closely,” Haney said.
Haney is the scientist in charge at the Alaska Volcano Observatory. He said researchers also observed that the surface of Mount Spurr was inflating outwards. Movements escalated in the summer when researchers saw snow on the summit of the volcano begin to melt and form a turquoise lake. Then on Friday and Tuesday, researchers flew over the volcano, where they sampled gases venting from the volcano.
Between the increase in gases, quakes, the melting of snow and the inflating surface, Haney said signs are pretty good that Spurr will erupt in the coming weeks or months.
“It's almost like we have a checklist of the usual signs that volcanoes give us before they progress to an eruption," Haney said. "And now we're seeing all four of those are giving us those indicators.”
Mount Spurr is about 80 miles west of Anchorage and the closest active volcano to Alaska’s population centers. It erupted twice historically, once in 1953 and again in 1992, when roughly a quarter of an inch of ash fell on Southcentral communities. The 1992 eruption resulted in the Anchorage airport closing for 20 hours.
“When we consider many different scenarios, including the scenario that the volcano may not ultimately erupt, or other eruption scenarios, we now consider it the most likely scenario to be eruptions like occurred in 1953 and in 1992 at Spurr,” Haney said.
Haney said the most likely scenario is an eruption not from the summit of Mount Spurr, but at an opening about two miles away called Crater Peak.
“The eruptions of Mount Spurr in 1953 and in 1992 were from Crater Peak," Haney said. "And when they flew around Crater Peak, they did not measure sulfur dioxide gas in excessive background there, but they did measure carbon dioxide, which is indicative of magma intruding beneath Mount Spurr in Crater Peak in particular.”
Spurr remains at a “yellow” advisory status, as it has since October, but Haney and other researchers now predict an explosive eruption, rather than lava running down the volcano.
“More often than not, we have explosive eruptions that fragment magma and shoot ash, you know, 50,000 feet into the atmosphere,” Haney said.
Those explosions could last for as long as a few hours and produce ash clouds carried for hundreds of miles.
That ash is known to shut down jet engines and cause severe damage to plane exteriors, and Ted Stevens Anchorage International Airport is one of the busiest air cargo hubs in the world. In December 1989, a KLM 747 jet flew through ash from another nearby volcano, Mount Redoubt, and the plane’s engines shut down, forcing an emergency landing in Anchorage with 231 passengers aboard.
On the ground, the most immediate hazard to nearby residents from a Mount Spurr eruption would be from ashfall, which could be carried by winds, State Division of Homeland Security and Emergency Management spokesman Jeremy Zidek said.
“Ash is not good for people to breathe,” Zidek said. “It’s not good for your skin. So what we want people to do during the volcanic eruption is really minimize their exposure to that ash as much as possible. Mask up if they do have to go outside.”
The ash can also impact visibility on the roads and damage vehicles, so residents should limit their driving in the event of an eruption, Zidek said.
Haney, the volcano researcher, said an eruption could come with “little or no additional warning” and pose a risk to people closer to the volcano, within about 15 or 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 said. "There can also be volcanic mudflows called lahars.”
Though the eruption has the potential to temporarily impact air travel, Zidek said he doesn’t anticipate widespread impacts.
“While we need to be mindful of it and take steps to prevent breathing it, we don't anticipate we're going to see widespread power outages (or) our water supplies being contaminated,” Zidek said. “We don't anticipate that air travel will be canceled for weeks.”
So, while Mount Spurr’s unrest comes with some risks, Haney said there should be ways for residents to see the eruption from a safe distance at Anchoage’s Point Woronzof.
“When it comes into Anchorage, it will be almost like a sandstorm with dark ash," Haney said. "It will, if it occurs in daylight, it'll block out the sun.”
If it comes at night, Haney said onlookers can be in for a different visual spectacle
“It can produce a large amount of lightning," Haney said. "We call it volcanic lightning. It's due to charges getting set up by the the ash particles scraping up next to each other.”
More information on how residents can prepare for an eruption is available on the state emergency division website.
