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#EBS story Seeing inside volcano eruptions


Volcanic eruptions are unpredictable; whilst sometimes they can be explosive, on other occasions lava flows and diffuses. Scientists are using the new BM18 to follow the eruption of a volcano live, in order to gain insights on the mechanisms leading to the different types of eruptions.

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During an explosive eruption, volcanoes eject thick, viscous lava, along with ash, rock fragments, and gases. These eruptions can be extremely dangerous and destructive. In contrast, during a lava flow eruption, runny lava flows from the volcano and spreads out over the surrounding landscape. The magma can also simply arrest in the conduit, releasing its driving gases and defusing the ongoing volcanic explosion.  Volcanoes around the world can have either of these eruptions, so it is important for the scientific community to find strategies to predict these natural events.

The type of eruption a volcano exhibits depends mostly on two parameters: the viscosity of the fluid and the pressure behind it. On its own, viscosity is highly dependent on the fraction of gases, crystals and liquid in the magma, their shapes, orientations and interactions. A small change in pressure and temperature can significantly change the overall ratios of these fractions and the overall fluidity. To date, research in this domain has been limited and there is no consensus on the exact conditions that can trigger a volcano in an explosive or non-explosive way.

“We want to reproduce the conditions inside the volcano and use different synthetic magmas with more or less crystals, and check how the magma climbs into the volcanic conduit when we increase the temperature”, explains Benoit Cordonnier, scientist at the ESRF’s new BM18 beamline.

“Thanks to the Extremely Brilliant Source capabilities, the new BM18 beamline and a specific sample holder, these experiments will provide us with a more faithful insight into what happens in the eruption, in comparison to previous research”, he adds. Specifically, the increased flux of EBS will enable the researchers to go through thicker material, i.e. rock, reproduce the conditions deeper in the volcano and perform faster scans.


The team with the set-up on beamline BM18. From left to right: Benoit Cordonnier, scientist at BM18, Clemence Muzelle, software engineer, and Benjamin Richer, engineer in the sample environment group.  Credits: M. Capellas Espuny

The set-up is complex and has required extensive work from the Sample Environment Group at the ESRF. “We started working back in 2021 with Benoit Cordonnier to try to mimic the events happening inside a volcano in the scale of a few millimetres”, explains Johannes Frey, engineer in the Sample Environment Group. “So we 3D printed a shell in a typical volcano shape in alumina, in which the sample (synthetic magma) would be enclosed and with only one way out: the top of the shaft”, he adds.

“Our set-up includes an induction furnace capable of warming up a 40mm long and 10mm wide sample holder, which is like a miniature volcano”, explains Benjamin Richer, engineer at the Sample Environment Group. “It can reach 1200 degrees Celsius, which is the temperature of the hottest magma, but it is also close to the limit of what our hardware can achieve, so we had to carry out many tests on material and configurations”, he adds. The only element missing in the volcano eruption scenario is the pressure behind the magma, but the team is already looking into possible solutions.

In particular, Cordonnier is analysing how the fluid of the magma, the bubbles and the crystals interact and move: “We can get direct visual on how magma changes with deformation, we can see whether bubbles stay isolated (which makes the eruption explosive) or join, creating channels that may defuse the volcanic bomb.” He adds: “Ultimately, we want to know how the crystal network influences the behaviour of the bubbles.”

The experiments the team is carrying out now are a proof-of-concept that may well lead to many breakthroughs in research on volcanoes. “This is a completely new way of studying eruptions and we are now open to the user community to apply for beamtime and contribute in expanding the knowledge in this field”, concludes Cordonnier.

Text by Montserrat Capellas Espuny

Top image: The "miniature volcano" on beamline BM18 during the experiment. Credits: B. Cordonnier.