Major volcanic eruptions might be driven by gas dissolving back into magma

Krystal Kasal

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Understanding what triggers large volcanic eruptions is crucial for hazard assessment, but the exact mechanism driving these eruptions is still poorly understood. The prevailing theory is that volatile exsolution—gas coming out of magma—is a main driver of eruptions, particularly in volcanoes rich in silica. However, a new study, published in Nature Communications, posits that it is actually gas being dissolved back into the magma that leads to the pressurization needed for large eruptions.

Volatile exsolution vs. volatile resorption

Previous research has emphasized volatile exsolution as a driver for eruption caused by increasing pressure in magma chambers. In volatile exsolution, dissolved gases, like water vapor, carbon dioxide and sulfur separate from a silicate melt to form bubbles as magma rises or cools. This decreases solubility, creating significant magmatic overpressure, which drives volcanic eruptions. Some previous studies have found that exsolved gases in large volcanic systems can actually buffer pressure, making eruptions less frequent, but larger when they do occur.

"However, for volatile exsolution to act as primary eruption trigger, exsolution must outpace both volatile loss by passive degassing and viscous relaxation of the crust. This, however, requires rapid crystallization rates that are difficult to maintain in larger, thermally buffered reservoirs. In large silicic systems, exsolved volatiles may therefore exert a primary control on magma compressibility and chamber growth, rather than directly triggering eruptions," the study authors explain.

The new study explores the opposite process, called volatile resorption, in which gases dissolve back into magma. The team says that this resorption reduces magma compressibility, modulating the system's response to recharge and its overall stability, which ends up expediting eruptions since it is harder to compress. Volatile resorption can rapidly increase pressure in large silicic magma chambers, potentially triggering eruptions faster than volatile exsolution.

Simulating the Aso caldera in Japan

The researchers use an ancient volcanic eruption in Japan as an example. They say that volatile resorption likely played a key role in Japan's Aso eruption, referred to as "Aso-4," which occurred around 86,000 years ago. To make this determination, the team used a thermo-mechanical numerical model of magma chambers, calibrated with geochemical data from the Aso volcano. A calcium phosphate mineral, called apatite, is spit out by such volcanoes and can serve as a record of water saturation behavior in the magma. Information gathered from Aso's apatite crystals helped to model how the eruption occurred.

The simulations tested out different recharge rates, volatile contents, and thermal conditions to see when volatile resorption occurs and how it affects chamber stability. The results showed that volatile resorption reduces magma compressibility, amplifying pressurization and destabilizing the chamber.

The study authors say the simulations show resorption results in eruption faster than cases involving exsolution. They write, "Looking specifically at the 5 wt% H₂O containing cases, we find that pressurization rate is substantially higher in the resorbing run and that this case experiences an eruption after ~2.3 kyrs, while the exsolving run does not undergo eruption within the 5 kyrs simulation time. The elevated pressurization rates during resorption are caused not only by higher recharge rates experienced in volatile resorbing runs, but also by a reduction in the magma compressibility stemming from the resorption-induced decrease in magmatic volatile phase (MVP) that usually buffers pressure build up in silicic systems."

Although these models simplify the mechanics of volcanoes to some degree and focus on one specific case, the team believes this study can serve as a jumping off point for future studies. Future studies may be able to refine understanding of volatile resorption with more complex models and real-time monitoring, ultimately offering a new way to predict catastrophic volcanic eruptions, potentially saving lives and reducing economic loss.

Written for you by our author Krystal Kasal, edited by Gaby Clark, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.

Publication details

Franziska Keller et al, Volatile resorption expedites eruption onset in large silicic systems, Nature Communications (2026). DOI: 10.1038/s41467-026-70206-8

Journal information: Nature Communications

Key concepts

magmavolcanic activityvolcanic eruption prediction

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