Scientists have made an important step towards understanding how volcanic eruptions happen, after identifying a previously unrecognised potential trigger.
The findings -- from the team of researchers from Monash University, and the Universities of Liverpool (UK) and Newcastle (Australia) -- could lead to new ways of interpreting signs of volcanic unrest measured by satellites and surface observations.
Understanding the triggers for volcanic eruptions is vital for forecasting efforts, hazard assessment and risk mitigation. With more than 600 million people worldwide living near a volcano at risk of eruptive activity, it is important that understanding of these complex systems and their triggering mechanisms is improved. There is also a strong economic incentive to understand the causes of volcanic activity -- as demonstrated in 2010 by the eruption of Eyjafjallajökull, Iceland -- which caused air-traffic disruption across Europe for more than one month, with an estimated US$1.8 billion loss in revenue to the airline industry.
Studying volcanic processes in nature can be challenging because of the remoteness of many volcanoes, the dangers to scientists wanting to study destructive eruptions up close, and the fact that they are often obscured from direct observation by volcanic ash or rock.
Professor Sandy Cruden, School of Earth, Atmosphere and Environment at Monash University, said to get around this difficulty the team recreated a scaled down version in the labs at Monash.
"We studied the plumbing systems of volcanoes by modelling how magma ascends from great depths to the surface through a series of connected fractures (called dykes and sills)," he said.
"To do this, we used a tank filled with gelatine (jelly) into which we injected coloured water to mimic ascending magma. We used a high-speed camera and a synchronised laser to observe what was going on inside the tank as the magma moved upwards."
Professor Cruden said it was at this point that they discovered a significant and previously unknown drop in pressure when the ascending vertical dyke stalled to form a horizontal sill.
"Sills often form in nature as part of a developing volcanic plumbing system, and a pressure drop can drive the release of dissolved gasses, potentially causing the magma to explode and erupt," he said.
"It's similar to removing a cap from a bottle of shaken soda - the pressure drop causes bubbles to form and the associated increase in volume results in a fountain of foam erupting from the bottle."
Volcano-monitoring systems around the world rely on the interpretation of signals of Earth's surface and subsurface measured by satellites, ground deformation devices and seismometers. These record when and how magma moves at depth and they are used to help determine the likelihood of an eruption occurring.
The new results will aid this effort by adding a previously unknown eruption triggering mechanism and by helping to improve understanding of the dynamics of magma ascent, which leads to eruptions.
The research was published in Earth and Planetary Science Letters.
The lead author was Dr Janine Kavanagh, Department of Earth, Ocean and Ecological Sciences, University of Liverpool, UK.
For more information please contact Rachael Fergusson, Monash Media on +61 3 9903 4841.