How does a volcano erupt, and how are eruptions predicted?

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1. 1

   Volcano (Wikipedia)

   WikipediaPublished Oct 15, 2026Checked Oct 17, 2026

   “A volcano is a vent or fissure in the crust of a planetary-mass object that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are diverging or converging, and because most of Earth's plate boundaries are underwater, most volcanoes are found underwater. For example, a mid-ocean ridge, such as the Mid-Atlantic Ridge, has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes resulting from divergent tectonic activity are usually nonexplosive whereas those resulting from convergent tectonic activity cause violent eruptions. Volcanoes can also form where there is stretching and thinning of the crust's plates, such as in the East African Rift, the Wells Gray-Clearwater volcanic field, and the Rio Grande rift in North America. Volcanism away from plate boundaries most likely arises from upwelling diapirs from the core–mantle boundary called mantle plumes, 3,000 kilometres (1,900 mi) deep within Earth.”

2. 2

   Triggering the 2022 eruption of Mauna Loa.

   Nature communications (Lynn et al.)Published Nov 12, 2024Checked Oct 17, 2026

   “After decades of intermittent seismic and geodetic activity over 38 years of repose, Mauna Loa began erupting on 27 November 2022. Here we present a multidisciplinary synthesis that tracks the spatio-temporal evolution of precursory activity by integrating mineral and melt chemistry, fluid inclusion barometry, numerical modeling of mineral zoning, syn-eruptive gas plume measurements, the distribution and frequency of earthquake hypocenters, seismic velocity changes, and ground deformation. These diverse data indicate that the eruption occurred following a 2-month period of sustained magma intrusion from depths of 3-5 km up to 1-2 km beneath the summit caldera, providing a new model of the plumbing system at this very high threat volcano. Careful correlation of both the geochemistry and instrumental monitoring data improves our ability to distinguish unrest from the run-up to eruption by providing deeper understanding of the both the monitoring data and the magmatic system-an approach that could be applied at other volcanic systems worldwide.”

3. 3

   Jerk, a promising tool for early warning of volcanic eruptions.

   Nature communications (Beauducel et al.)Published Dec 17, 2025Checked Oct 17, 2026

   “Forecasting volcanic eruptions remains a great civil defense challenge in many parts of the world. Although instrumental monitoring networks provide a variety of signals interpretable as eruption precursors, volcano observatories still lack a systemic warning tool that can issue unambiguous real-time alerts to stakeholders. Here, we propose such a tool called "Jerk" that permits real-time detection of subtle ground movements associated with magma injections. The Jerk signals consist of very low frequency transients in both horizontal ground motion and tilt which, we show, are generated by fracture openings prior to an eruption. These signals can be detected using one single broadband seismometer. Implementation of fully automated Jerk detection and analysis at Piton de la Fournaise (La Réunion island) has permitted real-time early warnings for 92% of 24 eruptions that occurred in 2014-2023, with alarm times ranging from a few minutes to 8.5 h before magma reaches the surface. The Jerk tool thus promises to be a successful early warning method for forecasting volcanic eruptions and provides a potential alternative for poorly monitored volcanoes.”

4. 4

   Near real-time b -value analysis for volcano traffic light alert systems and eruption forecasting.

   Scientific reports (Bantidi et al.)Published Jun 2, 2026Checked Oct 17, 2026

   “We introduce a 'Volcano Traffic Light Alert System (VTLAS)' to assess priming timescales and potential improvements to near‑real‑time forecasting. We define red light as instances when the b-value drops exceed 10% below normal background levels of activity and examine whether eruptions occur within 10 days. Of the 25 identified cases, 39% are followed by eruptions, whereas 61% are not. Among the latter, 71% involve red lights without subsequent eruptions but are mostly linked to large earthquakes, and 29% show no drop before an eruption. Despite the relatively low percentages, our forecasting success rate is comparable to that reported in studies employing InSAR, GNSS deformation, or thermal anomaly analyses. This suggests that the proposed VTLAS may help anticipate impending eruptions. However, to improve reliability, we recommend combining b-value analysis with other geophysical observables to effectively distinguish volcanic unrest from imminent eruptions.”

5. 5

   Socio-economic value of data-driven eruption forecasts to balance false alarms against catastrophic loss.

   Nature communications (Ardid et al.)Published Aug 26, 2026Checked Oct 17, 2026

   “The adoption of new forecasting methods for volcanic eruptions typically emphasizes predictive accuracy, often overlooking their potential to reduce overall life and economic losses. We introduce a Potential Economic Value (PEV) framework that evaluates forecast utility by balancing precautionary actions against avoidable catastrophic losses (such as mass casualties). Using machine-learning forecasts from continuous seismic data at five volcanoes, we show that non-forecasted eruptions (missed) have disproportionate consequences, compared to false alarms, which generate recurring and manageable disruption. Retrospective analyses of the 2019 Whakaari (New Zealand) and 2014 Ontake (Japan) eruptions, along with three additional volcanoes, indicate that losses could have been reduced by 30-90%, despite generating numerous false alarms. Across all case studies, effective forecasting prioritizes reducing missed eruptions over maximizing accuracy. This supports the use of more precautionary warning thresholds, provided that the resulting increase in alert frequency is managed in ways that maintain public compliance and trust.”