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The volcano watchmen

[Translate to Englisch:] Vulkane

An interdisciplinary team led by volcanologist Thomas Walter from the Helmholtz Centre Potsdam - German Research Centre for Geosciences GFZ is investigating in a new way how the slopes of volcanoes can start to slide or how sudden eruptions can occur. Chemical degradation processes in the rock play an important role and researchers hope that an efficient early warning system can even be developed on this basis.

When the eruption of a volcano in Iceland seemed imminent in mid-November 2023, countless "Tagesschau" viewers in Germany watched with feverish anticipation. The 4,000 inhabitants of Grindavík were evacuated and soon afterwards huge masses of lava poured out of the ground not far from the town. However, the dangers of such eruptions are enormous, and not just in Iceland. "Over 800 million people live in the vicinity of active volcanoes," says volcanologist Thomas Walter from the Helmholtz Centre Potsdam - German Research Centre for Geosciences GFZ.

The Lastarria stratovolcano is 5,697 meters high and lies on the border between Chile and Argentina. Photo: GFZ/ Thomas Walter

In the middle of the 19th century, researchers began to study volcanoes more closely. First and foremost, they wanted to find out how eruptions and other dangers announce themselves. However, despite all the advances in science and technology, there are still often unpleasant surprises: In the past ten years alone, natural disasters triggered by volcanoes have caused damage of around 4.5 billion euros worldwide. As part of the interdisciplinary research project "ROTTnROCK", experts led by GFZ scientist Thomas Walter now want to decipher what triggers eruptions, causes the slopes of volcanoes to slide or causes faults to suddenly become active.

It was previously assumed that changes in pressure inside volcanoes were the cause. Now, however, the focus is shifting to another factor. "We have discovered that hydrothermal alteration changes the strength of rocks and their permeability to fluids," explains Walter. "Such gradual processes inside volcanoes have long received little attention. However, they can be one of the main causes of unexpected hazards." Together with leading experts from Ireland, Sweden and France, team leader Walter is now getting to the bottom of this phenomenon. The EU is funding the project with an ERC grant worth ten million euros.

Like a tomato becoming rotten (mechanically weak) and changing its appearance, hydrothermal alteration changes the appearance of the volcano and the physical and chemical state of the rocks, creating a “rotten” volcano with an increased potential for explosive eruptions and collapse hazards. Graphic: GFZ/ Thomas Walter

The investigation of older volcanoes, where parts of the interior have been exposed by erosion, is an important approach. However, the experts also measure the topography of active volcanoes using drones and satellite radar and observe chemical changes on their surface using hyperspectral cameras. In addition, they regularly take rock samples during expeditions to the monitored volcanic areas in Europe and Asia and examine them in the laboratory. In order to clarify how quickly the "rotting" of volcanic rock occurs, they also expose the samples in the laboratory to fluids with very low pH values, for example, the highly acidic water from crater lakes, and observe the resulting changes. Artificial intelligence (AI) is used for the computer-aided detailed analysis of the chemical-physical processes in the rock structures.

The team also wants to find out how strongly hydrothermal alteration influences the stability of the rock. To this end a purpose built, robust, three-axis compression machine several meters high and made of acid-resistant materials is being made especially for the project.

Prof. Dr. Thomas Walter, working group leader in Section 2.1 "Earthquake and Volcano Physics" of the GFZ and professor at the University of Potsdam. Photo: private

"Last but not least, we are creating a digital image of all the volcanoes we are studying. We are constantly improving this using data obtained with the help of satellites such as the EnMAP hyperspectral satellite and drones from the air, or through chemical and mechanical measurements in the laboratory," says Thomas Walter: The 'digital twins' of the observed volcanoes will serve as an important basis for future predictive modeling. The long-term goal is that the knowledge gained will also be used to monitor all other volcanoes in the world.

Reliable forecasts of volcanic eruptions are still a vision. But Thomas Walter is brimming with optimism. "ROTTnROCK will change our understanding of hydrothermal alteration and its effects and help us to make much more precise predictions," he says. This would make it possible to evacuate or relocate settlements in the vicinity of volcanoes that have become unstable in good time, and prevent many a disaster.

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