Researchers dig into past Augustine volcano eruptions to better understand future threats
Mount Saint Augustine volcano is a familiar and majestic sight across Cook Inlet. It's also one of the most highly active in Alaska. Standing over 4,000 feet the lava dome volcano has erupted six times in the last two hundred years, most recently in 2006. Scientists are now looking into the past of the volcano to better understand its future.
Kristina Walowski is assistant geology professor at Western Washington University, working with a team of researchers and in collaboration with Alaska’s Volcano Observatory, and taking a look back at hundreds of years by looking at its layers.
“One of our goals is to better understand the eruptive personality of Augustine and specifically, we want to better understand eruptions that happened in the past,” Walowski said. “So eruptions that happened about 400 years ago, and about 800 years ago, seem to have left really sort of thick pumice layers on the island of Augustine.”
Augustine is one of the most frequently active volcanoes in Alaska. Walowski says she hasn’t encountered any written or oral history describing those volcanic eruptions hundreds of years ago, but they seemed to be unique.
“But they seem like they left a thicker pumice and ash deposit than eruptions that we've witnessed over the past 200 years,” she said. “So one of our goals is to better understand whether or not they were more explosive or more hazardous but also we really want to understand why that was the case. So what's happening beneath Augustine volcano, or in the plumbing system of the magma reservoirs that might result in a different erupted personality over time.”
Augustine volcano is an island, and Walowski says it’s a fairly young one in geologic time.
“In the grand scheme of things, most of the rocks on Augustine actually erupted in the last 25,000 years,” she said. “You might think that that's really old. But in terms of volcanoes, many volcanoes have eruptive lives of hundreds of thousands, to even half a million, or a million years. So we consider Augustine a fairly young volcano.”
To investigate the volcano’s plumbing, Walowski and her team joined Alaskan researchers on a field expedition last summer.
“So what we do when we go to a place like Augustine island, is we walk around and we actually dig a lot of holes,” Walowski said. “Or we dig into the sides of existing river drainages, or along coastal bluffs. And when we dig into the soil, what you start to see are these different layers that appear. But then after a layer of soil, we might see a foot of pumice, white pumice and ash. And then we might see another soil layer, and then another layer of pumice and ash. And so essentially, we dig into the past by digging holes deeper in time.”
Though much of her work is investigating the base, Walowski described flying by helicopter to the summit of Augustine, where the newest rock is from the most recent eruption.
“The summit of Augustine is pretty amazing. It’s a bit of a moonscape, in that it is all just raw rock, with some ice and snow.” she said. “And there are also these really large funerals, which is a place on a volcano where there are volcanic gasses exiting the volcano. And then there's like a bunch of really big spires of rocks that are jutting out. And also, Augustine is this amazingly perfect, conical shape, right? It's like this perfect, pointed, circular triangle thing. And so when you stand at the top, and you look over the edge, it's almost like you're gonna fall off the edge and your view of the island is just this little bit of coastline all around you. So it feels really unique to being on other mountain summits, where you do really feel like you're sort of at the top of the pin, looking down at the Cook Inlet around you.”
Walowski says her work does not involve monitoring or predictions, but hopes her research, due out next year, will shed light on the past eruptions and what might happen in the future.
“A hypothesis for the triggering of some eruptions is, usually there's one magma reservoir, and then a new magma, which is hotter and fresher gets injected into that magma reservoir, and it causes mixing. And that sometimes can trigger eruptions,” she said. “So one of the hypotheses we're trying to test is how that process of mixing may be different for the older eruptions. There's some differences in how the mixing of magmas occurs before eruption in the older eruptions compared to the newer eruptions.”
The Alaska Volcano Observatory monitors Augustine closely. Matt Loewen is a research geologist, and explained the volcano monitoring system uses many tools.
“We have seismic instruments on the flanks of the volcanoes and around them, and then those have radio links, which send that data in real time back to our office,” Loewen said. “And if those volcanoes have small earthquakes underneath them, that can be a sign that magma is moving and an eruption is coming. But we also use remote sensing data like satellite images, we have webcams, we look at deformation, and a lot of different data streams.”
Loewen says Augustine is one of the most potentially dangerous in the case of an eruption, because of its proximity to the Kenai Peninsula and Anchorage. He says the main threat is ash fall impacting air travel and aviation, as well as respiratory health. In that case, geologists monitoring closely would be able to quickly put out the alert to the public.
“We've seen it erupt before, we kind of know it's eruptive style, we know it's unrest styles, and we have really good monitoring equipment on it,” he said. “There’s a very good chance that we'd be able to issue basically a forecast that an eruption was possible in the distant future, in the near future, and then maybe even at the last minute, that eruption was about to happen, and then certainly detecting it.”
Between daily monitoring and ancient observation, researchers say the hope is that if Augustine does erupt again the public would have more warning and be better prepared.