# From magma to macrophage: the grand challenges of volcanic environments

Catherine A Mériaux, Edward Ntim Gasu, Guillaume Nyagatare, Vicky Ruganzu, Philbert Ntivuguruzwa, Mwumvaneza Mutagoma, Atalay Ayele, Julyan H E Cartwright, Valérie Cayol, Laurent Charlet, et al.

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## To cite this version:

Catherine A Mériaux, Edward Ntim Gasu, Guillaume Nyagatare, Vicky Ruganzu, Philbert Ntivuguruzwa, et al. From magma to macrophage: the grand challenges of volcanic environments. Bulletin of Volcanology, 2026, 88, pp.22. 10.1007/s00445-026-01936-2. hal-05504536

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# From magma to macrophage: the grand challenges of volcanic environments

Catherine A. Mériaux¹ Ⓒ · Edward Ntim Gasu¹ · Guillaume Nyagatare² · Vicky Ruganzu³ · Philbert Ntivuguruzwa⁴ ·

Mwumvaneza Mutagoma⁵ · Atalay Ayele⁶ · Julyan H. E. Cartwright⁷,⁸ · Valérie Cayol⁹ · Laurent Charlet¹⁰ ·

Claudia Corradino¹¹ · Antonio Costa¹² · François Darchambeau¹³ · Timothy Davis¹⁴ · Arnau Folch¹⁵ ·

Benjamin Gilbert¹⁶,¹⁷ · Alexandra Tiaré Gourlan¹⁰ · Andrew J. Hogg¹⁸ · Derek Keir¹⁹,²⁰ · Silvia Massaro¹²,²⁷ ·

Tamsin A. Mather²¹ · Clive Oppenheimer²²,²³ · Carolina Pagli²⁴ · Virginie Pinel¹⁰ · Eleonora Rivalta²⁵,²⁶ · Alison Rust¹⁴ ·

Roberto Sulpizio²⁷ · Latifa Sarra Kazi Tani¹⁰ · Andrew W. Woods²⁸ · Davide Zanchettin²⁹

Received: 15 November 2025 / Accepted: 11 January 2026

© The Author(s) 2026

## Abstract

The interdisciplinary study of volcanic processes, which extend across all timescales and lengths, requires a multitude of approaches, ranging from analogue and numerical modelling to observations and fieldwork and extending to mathematics. A conference was held at the East African Institute for Fundamental Research, affiliated with the University of Rwanda, a country which, along with the Democratic Republic of Congo, presents a unique geodynamic context. Located along the East African Rift, an active seismic region, Rwanda is close to two of Africa's most active volcanoes, including Nyiragongo, which overlooks Lake Kivu, a deep volcanic lake rich in dissolved carbon dioxide and methane, the latter of which is used for electricity generation. In this context, the conference addressed many “classic” volcanological topics and their modern advances, such as multiphase lava flows, subsurface magma propagation, seismic and deformation signals from a volcano, modelling of volcanic emission dispersion, and volcanic lakes. Yet, it broadened the discussion to the volcanic particle-water interface and its impact on soils, volcanoes and climate change, and volcanoes and health. This article aims to highlight and share the richness of the integration and interconnectedness of the various questions related to a volcanic environment, as well as their impact on society. Ultimately, this conference also demonstrated the importance of promoting science in Africa and developing countries so that the next generation of African researchers is equipped to address the challenges facing their nations.

**Keywords** Volcanology · Volcanic eruptions · Volcanic processes · Natural Hazards · Climate change · Volcanic soils · Environmental Health

## Introduction

Since 1841, when the first volcanic observatory was founded on Mount Vesuvius (Italy), monitoring has been at the heart of volcanic hazard assessment. Increasingly, field observations are integrated with satellite remote sensing, laboratory analysis and analogue and computational modelling to deepen our understanding of volcanoes and the magmatic systems that feed them. It is estimated that up to 800 million people worldwide are threatened by volcanoes. Hazards

include lava, pyroclastic and mud flows, ash clouds and fall-out, seismicity and exposure to gas and particulate plumes. Past eruptions have resulted in substantial loss of life, and infrastructural and economic damage. On the other hand, volcanoes and volcanic landscapes provide agriculturally-productive Andisols, geothermal resources and geotouristic potential.

From Cameroon to Eritrea, eastern and central Africa host many volcanoes that represent both risk and reward, yet the pace of disaster preparedness and development of resource opportunities has been slowed by wider challenges faced across much of the continent: conflict, health and economic inequality and impacts of climate change (Lenhardt and Oppenheimer 2014). A unique conference exploring

Editorial responsibility: M. Edmonds

Extended author information available on the last page of the article
these themes was held at the East African Institute for Fundamental Research in Kigali (https://eaifr.ictp.it) in September 2025. It drew locally-based staff, students and health professionals, regionally-based geophysicists, and scientists of diverse persuasions from Asia, Europe and North America (Fig. 1). A primary aim was to provoke discussion between students and experts and to showcase the research capacity in the region. Here, to stimulate further international engagement, we provide a digest of the topics covered by the meeting and highlight the tremendous potential for new collaborations aimed at tackling both fundamental and applied aspects of volcanic risk management, methane harvesting, agronomy and environmental health.

## Studying volcanic processes and their implications

Volcanic processes involve complex multiphase flows, ranging from subsurface mixtures of melt, crystals and bubbles, controlled by viscous stresses, to much faster-moving, inertia-controlled flows of fragmented solid particles suspended in hot, pressurized gas. Important phase transitions occur as

the continuous phase changes from liquid to gas by decompression, or from liquid to solid by cooling and crystallization (Edmonds & Woods 2018). Understanding how these mixtures evolve under changing conditions has advanced considerably through the development of models for phase transitions as the melt cools, decompresses, and progressively crystallizes on ascent. In addition, models have been developed for the saturation and exsolution of volatile compounds that accompany cooling and crystallisation. A key future development is the integration of these models with magma intrusion models.

A key challenge for hazard assessment is forecasting of the location, timing and nature of eruptive phenomena, which requires reliable models for the subsurface storage, transport and degassing of magma. Today, analogue, theoretical and numerical approaches that simulate magma trajectories from depth to the surface in different tectonic regimes, accounting for the influence of regional stress fields, topographic loading and unloading, magma buoyancy, viscous stresses, fracture resistance and solidification. An example of recent success has been the use of static models to capture the subsurface path of the Nyiragongo (East African Rift) magmatic intrusion (Pinel and Mériaux 2025). Further

<figure><img src="image_3.png" /><figcaption>**Fig. 1** Group Photo of the conference. Photo Credit: Philbert Ntivuguruzwa</figcaption></figure>

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recent developments have enabled exploration of the relationships between magmatic intrusion and the associated spatio-temporal patterns of seismicity and ground deformation. However, magma cooling and phase transitions during tortuous dike propagation in complex stress settings remain largely unexplored.

Seismic activity and surface displacements are crucial indicators of subsurface magma propagation. Surface displacements can be directly measured using geodetic techniques (InSAR, GNSS). The increasing availability of satellite data and improvements in time-series analysis enable measurement of displacements of just a few mm/yr over areas 100 s km wide every few days (Pagli et al. 2014). Displacements are rapidly analyzed via 3D inverse models to estimate the geometry and stress changes of the source of displacement (Smittarello et al. 2019). Identification of high frequency (volcano-tectonic) earthquakes provides a proxy for magma ascent, while low frequency seismicity can reveal processes in the volcanic conduit and deep pulses of volatile-rich basaltic magmas rising from the mantle. Today, improved computing power and machine learning are facilitating automated data processing, accelerating analysis and revealing fine structures around pressurized magma bodies. Such monitoring and analytical capabilities can provide vital early warnings of volcanic unrest and potential eruptions.

Volcanoes release ash, gas, and aerosols into the atmosphere forming plumes that can spread great distances with the winds. Atmospheric chemistry-transport models are used to simulate ash cloud dispersion, sulfate aerosol formation and tephra fallout. Different strategies are adopted for short-term forecast vs long-term hazard assessment, the former driven by weather prediction models and real-time observations, the latter by wind statistics and stratigraphic and sedimentological data. Advances in short-term forecasts include ensemble-based runs, assimilation of satellite and real-time monitoring data, and modelling of ash resuspension. For long-range hazard assessment, High Performance Computing (HPC) models allow full probabilistic treatments. Digital twins, AI and novel software engineering technologies promise further support for operational forecasting. In particular, Machine Learning and Deep Learning can reveal rules and patterns from data without explicit human supervision (Corradino et al. 2024). The uptake of these emerging approaches demands multidisciplinary skills and deeper understanding of underlying processes.

The Virunga region is renowned both for the prevalence of lava lakes at Nyiragongo and Nyamuragira volcanoes, and the vast, strongly stratified Lake Kivu. Magma degassing can result in accumulation of bubbles in subsurface sills and microlite formation. The near-surface increase in melt viscosity can provoke intermittent gas explosions (Strombolian eruptions). In contrast, water-filled lava lakes contain dissolved CO₂ or CH₄ at depth, which, if destabilized, can

release hazardous bubble plumes. The possibility of such limnic eruptions being triggered by subaqueous fissure eruption at Lake Kivu (DRC-Rwanda) has been a particular concern. There is also interest in the potential impacts of methane harvesting, which is underway on the lake, for energy generation. Bubble plume modelling has evolved from pioneering work that described the bulk motion of turbulent buoyant plumes to double-plume models incorporating stratification, bubble expansion and dissolution, and chemical reaction, and computational fluid dynamics (Cardoso and Cartwright 2024).

Volcanic soils result from both the bio-weathering of bedrock (e.g. basalt) and atmospheric inputs of tephra (e.g., containing titanomagnetite) and volatiles (S, Se, halogens, trace metals). The acidity of these soils favors dissolution of primary particles by plants and microorganisms. Bioalteration rapidly releases plant nutrients, combining with good water retention, friability to contribute to the high fertility of these soils, but also transforms ash and pumice into secondary minerals such as aluminosilicate nanospheres, nanorolls, and nanotubes (Dahlgren et al. 2004). Coupling intensive analysis of pair distribution functions and reactive transport models with advanced observational techniques (e.g., scanning electron microscopy, laser-induced breakdown spectroscopy) is revealing the important mechanisms controlled by these nanoparticles.

Volcanism influences our planet's environment across a vast range of spatial (local to global) and temporal scales (from less than a year to 100 million years) and through numerous processes, such as, but not limited to, Large Igneous Provinces (LIPs), and short-lived large-scale explosive eruptions (Mather 2015). Explosive sulfur-rich volcanic eruptions are a leading cause of external forcing of climate and can perturb the Earth system for timescales ranging from years to decades. The stratospheric sulfate aerosol generated by major eruptions increases planetary albedo, resulting in surface cooling by radiative forcing and potential interactions with internal modes of climate variability such as ENSO. Climate observations, reconstructions, and simulations reveal complex dynamic responses in the coupled ocean-atmosphere-sea ice system. Consideration of volcanic forcing has not only contributed to interpretations of world history (Büntgen et al. 2026), it is now recognised as essential for future climate projections (Marshall et al. 2022).

Health risks associated with volcanic eruptions include trauma, respiratory effects of ash and gas inhalation, skin and eye irritation, and asphyxiation (from catastrophic CO₂ release associated with limnic eruptions or accumulation of CO₂ from soil degassing in sheltered terrain). Less understood are the impacts of chronic exposure to acid atmospheric plumes sourced by persistent degassing, e.g., from Nyiragongo lava lake), and exposure to mineral particles, which can lead to conditions such as podoconiosis, a
non-filarial form of elephantiasis caused by long-term bare-
foot exposure to soils of volcanic origin and their nanotubes.
Podoconiosis affects more than 4 million people worldwide,
in severe cases leading to chronic lymphoedema of the lower
legs and inflammation (Deribe et al. 2018). Recent stud-
ies have found elevated aluminium, silicon, and titanium in
affected tissues, suggesting absorption of soil mineral par-
ticles. Macrophages play a key role in the immune response
by internalizing these particles, but when the digestive vesi-
cle ruptures and releases toxins, inflammation is triggered.
Podoconiosis exemplifies an environmental disease rooted
in the interactions between volcanic soil particles, genetic
predisposition, and sociocultural factors including footwear
and hygiene. Addressing it requires an interdisciplinary
approach integrating volcanology, biomedical research, and
public health.

Concluding remarks

Throughout the Kigali conference, the importance of inte-
grating different approaches to understand the processes
and impacts of volcanism was evident, including analogue
and computational modelling, observations and fieldwork,
and mathematical theory (See Supplementary Information).
The diverse applications of this knowledge—from analysis
of hazards and risks, to evaluation of energy futures, crop
yield experiments, soil bio-weathering, and environmental
toxicology—were striking. We invite readers of this report
to engage in more strategic and integrative thinking about
the challenges and opportunities of the geosciences, aimed at
supporting risk management, land use planning, sustainable
development of energy and geo-resources, environmental
health, and agronomy in volcanic regions, and encourage
especially new thinking and collaborative research on these
topics in eastern and central Africa.

**Supplementary Information** The online version contains supplementary material available at https://doi.org/10.1007/s00445-026-01936-2.

**Acknowledgements** The organising committee of the conference thanks all the sponsors of the conference including the Rwanda National Council for Science and Technology (NCST, project WALL, Grant ID: GCRW-CL001), the Fond Equipe France (FEF) of the French Embassy in Rwanda (FEF-R KIGASA), the International Geoscience Programme (IGCP-UNESCO; Project 767), the National Institute of Geophysics and Volcanology (INGV, Italy), the Institute for Research for Development (IRD; JEAI E-DOORS), the Groupe Interdisciplinaire GDR-Rift (France), the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI), the East African Institute for Fundamental Research and the Abdus Salam International Centre for Theoretical Physics. This is contribution no. 741 of the ClerVolc program of the International Research Center for Disaster Sciences and Sustainable Development of the University of Clermont Auvergne. CP is supported by the Space It Up project funded by the Italian Space Agency (ASI) and the Ministry of University and Research (MUR) under contract n. 2024-5-E.0 CUP n. I53D24000060005. CC is

supported by the Space It Up project funded by the Italian Space
Agency (ASI) and the Ministry of University and Research (MUR)
under contract n. 2024-5-E.0 CUP n. I53D24000060005.

**Funding** Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This conference has been supported by the Rwanda National Council for Science and Technology (NCST, project WALL, Grant ID: GCRW-CL001), the Fond Equipe France (FEF) of the French Embassy in Rwanda (FEF-R KIGASA), the International Geoscience Programme (IGCP-UNESCO; Project 767), the National Institute of Geophysics and Volcanology (INGV, Italy), the Institute for Research for Development (IRD; JEAI E-DOORS), the Groupe Interdisciplinaire GDR-Rift (France), the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) and the East African Institute for Fundamental Research.

Declarations

**Competing interests** The authors declare no competing interests.

**Open Access** This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

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Authors and Affiliations

Catherine A. Mériaux¹ Ⓓ · Edward Ntim Gasu¹ · Guillaume Nyagatare² · Vicky Ruganzu³ · Philbert Ntivuguruzwa⁴ · Mwumvaneza Mutagoma⁵ · Atalay Ayele⁶ · Julyan H. E. Cartwright⁷,⁸ · Valérie Cayol⁹ · Laurent Charlet¹⁰ ·

Claudia Corradino¹¹ · Antonio Costa¹² · François Darchambeau¹³ · Timothy Davis¹⁴ · Arnau Folch¹⁵ ·

Benjamin Gilbert¹⁶,¹⁷ · Alexandra Tiaré Gourlan¹⁰ · Andrew J. Hogg¹⁸ · Derek Keir¹⁹,²⁰ · Silvia Massaro¹²,²⁷ ·

Tamsin A. Mather²¹ · Clive Oppenheimer²²,²³ · Carolina Pagli²⁴ · Virginie Pinel¹⁰ · Eleonora Rivalta²⁵,²⁶ · Alison Rust¹⁴ ·

Roberto Sulpizio²⁷ · Latifa Sarra Kazi Tani¹⁰ · Andrew W. Woods²⁸ · Davide Zanchettin²⁹

Catherine A. Mériaux
cmeriaux@eairfr.org

Julyan H. E. Cartwright
julyan.cartwright@csic.es

Arnau Folch
afolch@geo3bcn.csic.es

¹ The East African Institute for Fundamental Research,
University of Rwanda, Kigali, Rwanda

2 Soil Department, School of Agriculture and Food Science, College of Agriculture Animal Science and Veterinary Medicine, University of Rwanda, Musanje, Rwanda

3 Rwanda Agriculture and Animal Resources Development Board (RAB), Huye, Rwanda

⁴ Feelpicturess Ltd, Kigali, Rwanda

5 Mugonero Hospital, Gishyita, Rwanda

⁶ The Institute of Geophysics Space Science and Astronomy,
Addis Ababa University, Addis Ababa, Ethiopia

7 Instituto Andaluz de Ciencias de La Tierra, Consejo Superior de Investigaciones Científicas, 18100 Armilla, Granada, Spain

Instituto Carlos I de Física Teórica y Computacional,
Universidad de Granada, 18071 Granada, Spain

9 Laboratoire Magmas Et Volcans, Université Clermont Auvergne, CNRS, IRD, OPGC, 63038 Clermont-Ferrand, France

10 University Grenoble Alpes, University Savoie Mont Blanc, CNRS, IRD, University Gustave Eiffel, ISTerre, 38000 Grenoble, France

11 National Institute of Geophysics and Volcanology (INGV), Sezione di Catania, Catania, Italy

12 National Institute of Geophysics and Volcanology (INGV), Sezione di Bologna, Bologna, Italy

13 Hydrichtis SRL, Ocquier, Belgium & KivuWatt Ltd, Kigali, Rwanda

¹⁴ School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK

15 Geociencias Barcelona (GEO3BCN-CSIC), Barcelona, Spain

16 Lawrence Berkeley Laboratory, Berkeley, USA

17 University of California, Berkeley, USA

18 School of Mathematics, University of Bristol, Fry Building, Woodland Road, Bristol BS8 1UG, UK

19 Department of Earth Sciences, University of Florence, Via Giorgio La Pira, 4, 50121 Florence, Italy

20 School of Ocean and Earth Science, University of Southampton, European Way, Southampton SO14 3ZH, UK

21 Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK

22 Earth Sciences Department, University of Cambridge,
Downing Street, Cambridge CB2 3EQ, UK

23 Osservatorio Etneo, Istituto Nazionale Di Geofisica E
Vulcanologia, Catania, Italy

24 Department of Earth Sciences, University of Pisa, Pisa, Italy

25 Section of Geophysics, Department of Physics and Astronomy, University of Bologna, V.Le Berti Pichat 8, 40126 Bologna, Italy

26 Division: Section 2.1 “Physics of earthquakes and volcanoes”, GFZ Helmholtz Centre for Geosciences, 14473 Telegrafenberg, Potsdam, Germany

27 Department of Earth and Geoenvironmental Science,
University of Bari, Bari, Italy

28 Institute for Energy and Environmental Flows, University of Cambridge, Madingley Road, Cambridge CB3 0EZ, UK

29 Department of Environmental Sciences Informatics and Statistics, University Ca'Foscari of Venice, Via Torino 155, 30172 Venezia Mestre, Italy