Collapse-Driven PDCs at Fuego Volcano: Investigating the March 2025 Eruption and Establishing Monitoring Framework

Fuego volcano (Guatemala) is one of the world’s most active volcanoes. One hazardous process that occurs on its steep slopes is the collapse of accumulated volcaniclastic material, triggering fast-moving and destructive pyroclastic density currents (PDCs). These flows can travel >10 km, destroying everything in their path. In June 2018, such an event resulted in over 430 fatalities, demonstrating the urgent need for improving our understanding of the flow triggering mechanisms. This project will investigate the eruption of Fuego on 9–10 March 2025, which triggered collapse-generated PDCs with runouts exceeding 6 km. While eruptions at Fuego are closely monitored, the gradual build-up and sudden failure of oversteepened hot volcaniclastic piles (volcanic blocks, ash, and lava flows) is not. The triggering processes remain poorly understood, and collapse-generated PDCs can produce volumes far exceeding those expected from eruption size alone, making them a critically overlooked hazard. This research aims to constrain the accumulation rates and failure conditions of volcanic material that lead to collapse. By initiating surveys of material stored on Fuego’s flanks, we will enable an assessment of the local collapse hazard and potential PDC volumes and runout distances according to the conditions of the upper flanks of the volcano. Our objectives are to: Map the 9–10 March deposits and collapse scars to determine the volume of material that accumulated and failed. Geomagnetic thermal proxy analysis on PDC deposit samples will be used to help determine accumulation rates and residence time of material on the volcano. Carry out surveys to establish a monitoring baseline for hot material accumulation over time to understand how it builds up between eruptions. Evaluate critical conditions for collapse and trigger mechanisms across multiple cycles through a timeline catalogue of past accumulation-collapse cycles. Assess the relationship between slope loading, collapse volumes, and PDC runout distances to improve hazard prediction and assess the current and future hazard. Immediate fieldwork is crucial, as the rainy season beginning in late May will rapidly erode the deposits, losing key information. By integrating field investigation, high-resolution drone mapping, satellite imagery, and past eruption data, we will reconstruct material build-up and collapse cycles and identify critical thresholds for collapse initiation. The project will contribute towards hazard assessment at Fuego, where >50,000 people live within 10 km of the volcano’s crater. However, the process occurs at other frequently active volcanoes worldwide, such as Arenal (Costa Rica), Merapi (Indonesia), Fuji (Japan), Stromboli and Etna (Italy). By identifying critical thresholds and monitoring risk levels for collapse-generated PDCs, this project will enhance monitoring capabilities, enabling improved hazard assessment and early warning information for an overlooked hazardous volcanic process. The outcomes of this work will potentially inform mitigation actions such as evacuation planning. This NERC Urgency project is time-sensitive and targets a rare opportunity, making it unsuitable for standard research funding routes. It will enable studying fresh deposits before they are lost, evaluating the critical collapse conditions leading to this kind of PDC and establishing a baseline for monitoring this hazard in the future. Our findings will improve fundamental scientific understanding of volcanic mass flows while supporting real-world volcanic risk reduction. This project brings together a team with expertise in mass flow dynamics, remote sensing, and volcanic hazards, ensuring both scientific impact and practical applications for disaster risk reduction.