Volcán de Fuego in Guatemala is one of the most active volcanoes in the world. Its frequent eruptions are spectacular to watch, but they also gradually build steep deposits of ash and lava fragments on its flanks. From time to time, this material becomes unstable and collapses, sending hot flows known as pyroclastic density currents (PDCs) often 5 to 10km, sometimes more than 10km, down the slopes of the volcano.

While eruptions at Fuego are closely monitored, these collapse-generated flows remain less understood. Our project, funded through a NERC Urgency Grant, is a collaboration between Guatemalan scientists, local institutions and international partners to investigate the timing and monitoring of these collapses.

Fieldwork in the rainy season

This project focuses on the 9 to10 March 2025 eruption, which generated PDCs with runouts exceeding 6km. In August 2025, we travelled to Fuego to study the deposits left behind. Our work combined field mapping and sampling with drone surveys and satellite imagery, but this was a race against time: Guatemala rainy season quickly erodes the evidence.

Our main study site was the Ceniza ravine, a valley that channels many of Fuego flows. Using satellite images, we identified deposits from the March 2025 eruption. On the ground, we confirmed a few intact outcrops, which were unconsolidated and, months after the eruption, still hot.

Reading magnetic fingerprints

To understand these deposits better, we collected samples for particle-size analysis and geomagnetic thermal proxy analysis. This technique uses tiny magnetic minerals that are naturally present in rocks. When heated, their magnetic orientation resets to align with the Earth magnetic field and, once cooled, the orientation becomes locked in, like a tiny compass needle frozen in place. By measuring the magnetism of our samples, we can tell whether particles were hot when they came to rest. If they all point the same way, the deposits came directly from the eruption column. If the directions are random, the material had cooled long before and was likely part of older piles that later collapsed.

Geomagnetism therefore lets us trace the provenance of the material — whether it was born in the eruption or destabilised from older accumulations. This is crucial for hazard assessment, since collapses of stored flank material can generate larger flows than those expected from eruption size alone.

Drones and 3D models

Another key part of our work involved flying high-resolution drones along the flanks of the volcano to produce detailed 3D models of the ravines. Together with satellite imagery, these allow us to measure how much material is stored on the volcano and how this material changes over time. By repeating the surveys, we will be able to build a timeline of how volcanic material accumulates and when it becomes unstable.

Next steps

Back in the UK and with our partners abroad, we are now analysing the samples and drone data. Geomagnetic measurements and remote sensing data will allow us to extend our observations back in time. Together, these results will help us understand how much material can safely accumulate on Fuego flanks before it becomes unstable.

Ultimately, our aim is to develop a monitoring framework for these deposits, so that future collapses and the potential runout of associated PDCs can be anticipated more effectively. Although our focus is Volcán de Fuego, the same processes occur at other active volcanoes around the world, from Etna in Italy to Fuji in Japan.

While in Guatemala…

Guatemala is a spectacular country with volcanoes always on the horizon. We spent our nights after work at the Fuego observatory, where we could watch the volcano — and it put a show up for us! Playing football on the local pitch with the volcano in the background was also a highlight of our evenings.

It was a privilege to spend time with our Guatemalan colleagues and learn from their experiences of living alongside active volcanoes. Field days were demanding, often cut short by weather, but what more could a volcanologist want than to discuss volcanic processes as they unfold in front of you, with delicious food and the country famously strong coffee to end the day?

A collaborative project

The fieldwork was a collaboration between:

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• University of Edinburgh
• University of South Florida (USA)
• Institute for Scientific and Technological Research of San Luis Potos (Mexico)
• National Institute for Seismology, Vulcanology, Meteorology and Hydrology (INSIVUMEH, Guatemala national monitoring institute)
• Coordinating Agency for Disaster Reduction (CONRED, the national civil protection agency)

The project also includes colleagues from the University of Liverpool and Michigan Technological University (USA).

The monitoring carried out by INSIVUMEH was essential for managing risks during our campaign, especially afternoon rainstorms that often trigger lahars (volcanic mudflows) in our study area. Their expertise and guidance, based on daily experience working on Fuego, allowed the team operate safely in the field.

About the author

Mexico City is one of the world’s largest cities and its population, geographical setting and aging infrastructure have put its natural water reserves at risk. Climate change and a growing population are forecast to put further strain on these reserves, making water crises and water poverty increasingly common. Long-term solutions need to look beyond purely technical water-management solutions and integrate sociological processes into future practices.

Socio-hydrological resilience

Socio-hydrology looks at the interactions between people and water, providing a holistic platform to better understand the impacts of water-management practices.

Making cities more socio-hydrologically resilient reduces the potential for water crises in the future. Working with the and the , BGS developed a tool for assessing the socio-hydrological resilience of cities, both currently and under various scenarios. This tool allows decision makers to assess the effects of changing water-management practices.

With guidance from local stakeholders, the team looked at how different climate-change scenarios could affect the socio-hydrological resilience of the city and how the development of household-scale wetlands across the city could improve this resilience. These ‘constructed wetlands’ consist of small areas of vegetation, soil and organisms that have been engineered to act as a biofilter to remove pollutants from water. They provide a decentralised, sustainable way to treat waste water, reducing disease and the need for infrastructure maintenance whilst improving access to green infrastructure, thus providing ecological benefit.

Mexico City today

The socio-hydrological resilience of Mexico City is currently divided into two main areas. The central and western parts of the city are generally more resilient, whilst the eastern, northern and southern neighbourhoods are less so. In the east and north, this lower resilience is attributed to a reduced capacity for society to adapt to water crises, but in the south, there is greater natural stress on water resources.

The development of constructed wetlands across the city has, under today climate, the potential to decrease the number of people vulnerable to water poverty by 32 per cent (around six million people). Wetlands also have the ability to decrease the number of highly vulnerable people by half a million.

Mexico City in the future

The project found that, with no improvements to water sustainability, around four million people in Mexico City will move from low to moderate vulnerability by 2050. These people will have greater difficulty gaining access to a reliable, clean water supply. Additionally, around seven in every ten people in the city would be classed as highly vulnerable, meaning that they are highly unlikely to have a secure water supply. The team found that optimising the development of constructed wetlands can improve socio-hydrological resilience in the future, bringing levels in line with those that we see today.

​Although constructed wetlands have the ability improve socio-hydrological resilience across Mexico City, they will need to be combined with other, decentralised green-blue infrastructure, such as rain-harvesting systems, to further improve resilience in the future.

Access the .

Partners and funding

This project was funded by British Council Institutional Links and developed in collaboration with the Architectural Association School of Architecture and the Bartlett Centre for Advanced Spatial Analysis (CASA), a research centre at University College London.

About the author

Guatemala is exposed to multiple natural hazards, including earthquakes, volcanic eruptions (and all their associated hazards, such as ash, lava flows, pyroclastic density currents and lahars), tsunamis, landslides, floods, droughts, ground collapse, tropical storms and hurricanes, extreme temperatures, and forest fires. The impacts of these hazards threaten economic growth, lives and livelihoods. Theranked Guatemala fourth globally in terms of the risk of becoming a disaster victim due to an extreme natural event.

Natural hazards (in Guatemalaand elsewhere) do not always occur independently, and there can be . One hazard may trigger multiple secondary hazards, which can subsequently trigger further hazards. For example, in Guatemala, regular eruptions of the volcano Santiaguito (pictured) result in large volumes of volcanic debris. This debris can be mobilised as lahars, and enter the hydrological system, triggering erosion and flooding, with the potential to damage important infrastructure.

Understanding potential interactions and chains of interactions can help to improve disaster preparedness and response. One way to do this is through constructing comprehensive and systematic frameworks of hazard interactions, i.e. visual matrices of primary hazards and potential secondary hazards. During his NERC/ESRC funded PhD, Joel Gill spent two months in Guatemala collecting evidence of potential hazard interactions, and constructing frameworks of hazard interactions in Guatemala at national and sub-national scales.

Sharing the research

Through the BGS Innovation Flexible Fund, Joel recently travelled back to Guatemala to share this work and discuss with partners how government agencies responsible for hazard monitoring and disaster reduction could use frameworks of hazard interactions. An important step in the research process, and an ethical responsibility for scientists, is communicating and sharing our work with stakeholders, including those who have contributed to the research and those who may benefit from its results.

During his visit, Joel presented the hazard interaction frameworks in Guatemala through seminars, workshops and meetings at universities, the  (INSIVUMEH), the  (CONRED), and the Guatemalan branch of the UN Office for the Coordination of Humanitarian Affairs.

The scientific and risk professional teams in Guatemala work under difficult conditions to protect lives and livelihoods. This project directly supports the , which calls for new ‘multi-hazard’ approaches that characterise and integrate information about hazard interactions. At the heart of the UN Sendai Framework for Disaster Risk Reduction (and the Sustainable Development Goals) are international cooperation and respectful partnerships.

Multiple partners identified the value of Joel’s frameworks as reference tools in both disaster response and preparedness. For example, some participants noted their use in informing public communications regarding potential secondary hazards after a primary hazard. Others observed interactions in the matrix that they had not previously considered, but they acknowledged could occur and that they could integrate into their planning. All partners agreed that a priority next step would be developing tools that inform municipal level planning and preparedness.

Joel finished his time in Guatemala by meeting the British ambassadors to Guatemala and Honduras, sharing the results of the meetings, and discussing disaster risk reduction in the region. Everyone agreed that there is significant scope for future collaboration between hazard scientists and disaster professionals in the UK and Guatemala.

Funding

Original research funded by a studentship grant from NERC/ESRC (NE/J500306/1). This work was continued through BGS Innovation Flexible Funding (2017/18) awarded to Joel Gill (BGS Global) and Katy Mee (BGS GeoAnalytics and modelling).