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Some volcanoes don’t give much — or any — warning before they blow. Veniaminof, Alaska, is one of them: it is a ”stealthy” volcano, which doesn’t show the traditional warning signs of an impending eruption, like the ground deforming or earthquakes.

Now scientists at the University of Illinois and ��ɬֱ�� have developed a way of modeling Veniaminof’s behavior, which could more effectively monitor potential eruptions and provide warning to people in the path of danger. Many stealthy volcanoes, like Stromboli in Italy or Popocatépetl in Mexico, are close to major air routes or large communities, so this modeling could save lives.

A study on the findings was published in .

“Understanding stealthy systems like Veniaminof is crucial not only for Alaska, but for similar volcanoes worldwide,” said , Shuler-Foscue Chair at ��ɬֱ��'s Roy M. Huffington Department of Earth Sciences who was a co-author of the study.

“Our work helps explain how this happens, by identifying the key internal conditions — such as low magma supply and warm host rock — that make eruptions stealthy,” said of the University of Illinois Urbana-Champaign, lead author of the study. 

Volcano warning signs

Veniaminof is an ice-clad volcano in the Aleutian Arc of Alaska. It’s carefully monitored, but only two of its 13 eruptions since 1993 have been preceded by enough signs to alert observing scientists. In fact, a 2021 eruption wasn’t caught until three days after it had started.

“Veniaminof is a case study in how a volcano can appear quiet while still being primed to erupt,” said Li. “It is one of the most active volcanoes in Alaska. In recent decades, it has produced several VEI 3 eruptions — moderate-sized explosive events that can send ash up to 15 km high, disrupt air traffic, and pose regional hazards to nearby communities and infrastructure — often without clear warning signs.” 

To better understand Veniaminof, the scientists used satellite radar () and computer modeling over three summer seasons before and throughout the 2018 stealthy eruption, which produced only ambiguous warning signs immediately before it happened. They created a model of the volcano’s behavior in different conditions which would change the impact of a filling magma reservoir on the ground above; then they compared the models to the data to see which matched best, and which conditions produced eruptions, stealthy or otherwise.

The researchers found that magma movement at Veniaminof can occur so subtly — especially within small, deep magma chambers — that current monitoring technology may miss it entirely. Their simulations show that factors such as magma flux, the shape and size of the magma chamber, and the heat of surrounding rock all affect whether an eruption will be detectable, said Lu, who specializes in using sophisticated satellite imaging technologies like InSAR to detect subtle changes in volcanoes, landslides, coastal subsidence, and human-induced geohazards.

Time series of ground deformation from 2015 to 2018 (pre-, during- and post- 2018 eruption) generated by InSAR. Red represents upward movement while blue represents downward movement. Credit: Frontiers in Earth Science.

��ɬֱ�� postdoctoral researcher was also a co-author for this study.

The science of sneaky eruptions

The research team found that a high flow of magma into a chamber increases the deformation of the ground and the likelihood of an eruption. If magma is flowing quickly into a large chamber, an eruption may not occur, but if one does the ground will deform enough to warn scientists first. Similarly, a high flow of magma into a small chamber is likely to produce an eruption, but not a stealthy one. Stealthy eruptions become likely when a low flow of magma enters a relatively small chamber. Compared to observational data, the results suggest that Veniaminof has a small magma chamber and a low flow of magma.

The model also suggests that different conditions could produce different warning signs. Magma flowing into larger, flatter chambers may cause minimal earthquakes, while smaller, more elongated chambers may produce little deformation of the ground. But stealthy eruptions only happen when all the conditions are in place — the right magma flow and the right chamber size, shape, and depth.

However, when the scientists added temperature to their model, they found that if magma is consistently present over time so that the rock of the chamber is warm, size and shape matters less. If the rock is warm, it’s less likely to fail in ways that cause detectable earthquakes or deformation of the ground when magma flows into the chamber, increasing the likelihood of a stealthy eruption.

A promising direction for volcano forecasting

“To mitigate the impact of these potential surprise eruptions, we need to integrate high-precision instruments like borehole tiltmeters and strainmeters and fiber optic sensing, as well as newer approaches such as infrasound and gas emission monitoring,” said Li. “Machine learning has also shown promise in detecting subtle changes in volcanic behavior, especially in earthquake signal picking.”

At Veniaminof, taking measures to improve the coverage of satellite monitoring and adding tiltmeters and strainmeters could improve the rate of detection. In the meantime, scientists now know which volcanoes they need to watch most closely: volcanoes with small, warm reservoirs and slow magma flows.

“Combining these models with real-time observations represents a promising direction for improving volcano forecasting,” said Li. “In the future, this approach can enable improved monitoring for these stealthy systems, ultimately leading to more effective responses to protect nearby communities.” – Frontiers and ��ɬֱ��