An ice-clad behemoth among Alaska’s Aleutian Range mountains is sharing secrets about what makes some volcanoes tick — namely, ones that show little sign of erupting before they blow.
In a study published Tuesday in the journal Frontiers in Earth Science, scientists said they have discovered why Mount Veniaminof is so stealthy — and that information may help improve volcano forecasting and perhaps save lives.
Named after an 18th century Russian Orthodox priest, Veniaminof is what scientists call a “stealthy volcano,” one that offers practically zero warning that an eruption is imminent. These volcanoes generally do not exhibit the typical precursors to eruptions, which may include rumbling, earthquakes, gas and steam plumes, and swollen or hot ground surfaces.
Stealthy volcanoes can be especially hazardous when located close to population centers. Merapi in Indonesia, Galeras in Colombia, Stromboli in Italy and Popocatépetl and Colima in Mexico are examples, according to the paper.
Unlike its more urban counterparts, Veniaminof sits in the remote Alaska Peninsula, some 480 miles southwest of Anchorage. The nearest village, Perryville, lies about 20 miles to the south. Perryville’s population totaled 81 people at last count.
Veniaminof is one of Alaska’s most active volcanoes, with 13 recorded eruptions since 1993, according to the study. Unlike Mount Redoubt, which triggered a near-disaster in 1989 when a jet bound for Anchorage lost engine power after flying into an ash cloud before recovering, or Mount Spurr, which coated Anchorage in ash and prompted airport closures during its 1992 eruption, Veniaminof’s seismic activity has caused relatively little trouble for Alaska residents.
But its eruptions seem to come out of the blue. Of Veniaminof’s 13 eruptions in the past three decades, only two produced warning signs, and a 2018 eruption went undetected until three days after it started.
The paper’s lead author, Yuyu Li, a volcanology doctoral student at the University of Illinois Urbana-Champaign, found Veniaminof’s behavior fascinating but disturbing. Given that the volcano can send ash nearly 10 miles into the atmosphere without warning, with the potential for disrupting air travel or posing other hazards, Li wanted to know more.
She and her team analyzed open-source monitoring data over three summer seasons immediately before the 2018 eruption. They created a model to understand what factors influence the likelihood of Veniaminof erupting. They considered several parameters, including magma flow rates, magma volumes and temperatures, and reservoir depths and shapes.
In a phone interview on Tuesday, Li said she and her colleagues found that a high flow of magma, or molten rock, into what’s known as a chamber increases the chances of an eruption.
The volcano may not erupt. But if magma quickly fills the chamber and an eruption does occur, the ground will likely bulge or otherwise change shape, a process called deformation. That’s something scientists would be able to detect.
They also found rapid movement of magma into a small chamber is likely to produce an eruption capable of being detected, not one without warning.
Stealthy eruptions occur more often when a low flow of magna enters a relatively small chamber, according to the research.
The study’s results suggest that Veniaminof has a small magma chamber and a low flow of magma.
A chamber’s size and shape factor heavily into the equation. Minimal earthquakes occur when magma enters larger, flatter chambers, according to the research.
Elongated chambers seem to produce less ground disturbance or deformation. If the rock is warm, it’s less likely to crumble in ways that produce earthquakes.
Stealthy eruptions only occur when the precise conditions exist, involving the right magma flow and the right chamber size, depth and shape.
One of the paper’s big takeaways is that volcanoes with small, warm reservoirs and slow magma flows are among those that ought to be most closely watched.
Using the model created by Li and her colleagues and adding more instrumentation and real-time monitoring to stealthy volcanoes could help keep the public safer, Li said. It’s a recipe for opening the door to improved volcano forecasting.
Dave Schneider, acting scientist-in-charge at the Alaska Volcano Observatory, didn’t have a chance to read the full study on Tuesday. But from what he gleaned from the news release, he said AVO scientists will evaluate it and determine if any of the findings and recommendations should be implemented.
“The biggest hazard from any eruption in Alaska is ashfall and disruption to aviation,” said Schneider. “Anything we can do to help predict that is important, given the constraints we have in terms of being able to get things in the ground and be able to interpret the data.”
Other stealthy volcanoes in Alaska include Cleveland, Shishaldin and Pavlov. The National Volcano Early Warning System lists them, as well as Veniaminof and others, as high priority in terms of their threat level.
Highest on the threat list are Akutan, Augustine, Makushin, Redoubt and Spurr.
Logistics and finances don’t always allow for high-tech, costly instruments to be placed in as many spots as volcanologists would like or to the extent they would prefer to see.
“Resources are finite,” Schneider said.
Eruptions from stealthy volcanoes in Alaska also tend to be less explosive and life- and property-threatening than those from volcanoes offering ample warning signs, he said.
Right now, Spurr is by far more of an issue than Veniaminof for volcanologists. The volcano, located about 75 miles west of Anchorage, is currently in “code yellow” status. That means low-level unrest is occurring with small earthquakes continuing beneath the surface and a weak steam plume arising from the top.
If magma were to move closer to the surface and other eruption indications were present, like ground deformation or increased hot gases and vapor plumes, the threat level would rise and scientists would advise the public that an eruption is very likely.
In March, scientists predicted that Spurr would erupt within weeks or months but the threat has since lessened.