19.03.2025 | News

Volcanic eruptions defy predictions

3D images help understand intense volcanic eruptions and mitigate their consequences

More than 800 million people worldwide live near an active volcano. Some of these volcanoes cannot be accurately predicted by models. This is also true for the Colli Albani in Italy. An international team led by the University of Geneva (UNIGE), involving researchers from DESY and Helmholtz-Zentrum Hereon, is uncovering this mystery with an innovation: the analysis of crystals containing traces of the last eruption. The study published in the Journal of Petrology paves the way for new analytical methods in volcanology and strengthens hazard prevention.

The secret is in the magma

The Colli Albani are a ring mountain range of volcanic origin near the Italian capital Rome. Photo: Alessandro Musu

Monitoring volcanoes to predict their potentially devastating impacts requires a detailed understanding of the signals preceding an eruption. This task becomes challenging when a volcano defies prediction models - like the Colli Albani, located just 20 kilometers from Rome. Theoretically, the composition of its magma should lead to low-intensity eruptions. However, past eruptions paint a different picture.

Magma contains volatile substances, primarily water and carbon dioxide. As it rises to the volcano's surface, these volatile substances are released, and the more viscous the magma, the harder it is for the gas to escape. The retention of gas leads to a pressure increases and eventually to violent explosive eruptions.

Theoretically, the Colli Albani should not pose such a danger, as its magma is not very viscous. Nevertheless, there have been several intense eruptions, the last one 355.000 years ago, when it spewed immense amounts of glowing ash and molten rock into the atmosphere. To learn more, the UNIGE research team analyzed "melt inclusions" from the magma of the last eruption using X-ray radiation. These tiny magma droplets, only a hundredth of a millimeter in size, were enclosed within crystals before the explosion and preserved valuable clues about the magma's chemistry, its water and carbon dioxide content - key factors for explosiveness - as well as its temperature and pressure. In total, the researchers examined 35 crystals with 2000 inclusions.

An innovative approach to studying magma

Photomicrograph of a clinopyroxene crystal. This mineral formed in a magma chamber. Melt Inclusions (in black) are present in these crystals. Image: Corin Jorgenson

Scientists from UNIGE collaborated with several institutions, including DESY, the Universities of Rome Tre and Bristol, and the Helmholtz-Zentrum Hereon. Using the PETRA III particle accelerator ring at DESY, the team was able to create high-resolution 3D X-ray images of magma inclusions. PETRA III generates intense X-ray radiation to study matter at the nanoscale at various experimental stations, such as the one operated by Hereon, where the experiment took place (Imaging Beamline P05).

"This approach is a novelty in volcanology, especially in the study of melt inclusions. It opens up new perspectives in this field," explains Dr Corin Jorgenson, first author of the study and then a doctoral student at the Department of Earth Sciences of the UNIGE Faculty of Science, now a postdoctoral researcher at the University of Strathclyde, Scotland.

Valuable results for prevention

One of the most important discoveries was the presence of many large-volume bubbles of water and carbon dioxide in the inclusions. This suggests that the Colli Albani contained significant amounts of gas. "Due to the excess gas, the magma resembled a sponge that was compressed when additional magma accumulated in the reservoir and expanded rapidly at the onset of the eruption - both essential reasons for the unexpectedly strong and explosive eruption," explains Luca Caricchi, professor of petrology and volcanology at the Department of Earth Sciences of the UNIGE Faculty of Science, who led the research.

These results provide insights into the mechanism of the Colli Albani eruptions and underscore the importance of 3D imaging techniques with synchrotron radiation in volcanology. This approach, which can also be applied to other volcanoes, will deepen the understanding of magma storage and degassing while helping to improve the containment of volcanic hazards.