Washington — A new understanding of volcanic eruptions reveals that the dynamics of magma movement play a crucial role in how and when a volcano erupts. This fresh perspective challenges the long-held belief that gas bubble formation in magma primarily occurs during pressure drops while rising.
Researchers, including a team from ETH Zürich, have conducted simulations that illustrate how gas bubbles in molten rock can form not only from changes in pressure, but also due to shear forces acting on the magma. This finding could reshape insights into volcanic activity and improve hazard predictions.
To simulate volcanic behavior, the researchers used a viscous polymer that mimics the properties of molten rock and infused it with carbon dioxide. Observations during these experiments showed that bubble formation predominantly occurs near the conduit edges, where the liquid interacts with wall surfaces, generating friction and shear. This movement allows bubbles to nucleate even when pressure remains stable.
Olivier Bachmann, a volcanologist at ETH Zürich and co-author of the study, emphasized the significance of their findings, stating that the movement caused by shear forces can lead to bubble formation without necessitating a pressure drop. This is a critical discovery that adds complexity to the dynamics of volcanic eruptions.
The team’s research also suggests that magma with low gas content might still produce explosive eruptions if shear forces foster rapid bubble formation. Conversely, in gas-rich magma, early bubble development may lead to the creation of “degassing channels,” which could prevent explosive events by relieving gas pressure.
A prime example of this phenomenon is the 1980 eruption of Mount St. Helens. Despite containing gas-rich magma, the eruption commenced with a slow lava intrusion that caused significant deformation. The shear forces at work produced additional gas bubbles, allowing for an initial release of gas. Ultimately, a landslide opened the volcanic vent, resulting in a rapid pressure drop that triggered the explosive eruption.
Bachmann advocates for updates to existing volcanic models to incorporate shear forces, underscoring the need for a comprehensive approach to predicting volcanic activity and potential hazards.
The research findings, detailed in a recent study published in the journal Science, represent a significant advancement in understanding how different physical forces can influence volcanic behavior. This work foreshadows the potential for a deeper comprehension of eruptions worldwide, providing valuable insights for both scientists and communities living near volcanoes.
