Violent volcanic eruptions can lead to collapse of the solid lid above the drained magma reservoir and create a depression called a caldera.  Such caldera-forming eruptions are among the most devastating natural processes on Earth, threatening not only nearby settlements but also impacting upon the global climate. 

The study by PhD student Anne Schöpa and Dr Catherine Annen in Bristol's School of Earth Sciences shows that magma chambers required for caldera-forming eruptions might grow faster and with less initial magma input than previously thought, making the forecast of volcanic eruptions more problematic.

Anne Schöpa said: "It was previously believed that a gradual increase in the magma input could form a large magma chamber which is necessary prior to a big caldera-forming eruption.  However, our numerical heat flow models show that this is quite difficult with a continuously rising magma influx.

"Instead, the magma input has to increase drastically and almost instantaneously above the background magma flux in order to create a big magma reservoir.  This increases the difficulty of making volcanic eruption forecasts because precursors of an eruption such as ground deformation would be detectable just shortly before an eruption."

This investigation utilised computer based modelling simulations to provide information on the intrusion rates, with model constraints coming from recent dating of granite intrusions, thought to be the remnants of non-erupted magma.

Anne Schöpa continued: "We wanted to test whether large magma chambers can form during the construction of crustal intrusions.  However our study shows that only very specific conditions of magma recharge lead to large reservoirs of molten magma and more often than actually erupting, the magma remains in the crust and freezes becoming a granite intrusion like those exposed in Dartmoor and Cornwall."

The research was funded by the European Research Council (ERC).

Paper

'The effects of magma flux variations on the formation and lifetime of large silicic magma chambers' by Anne Schöpa and Catherine Annen in Journal of Geophysical Research – Solid Earth. 

The Cabot Institute

The Cabot Institute at the University of Bristol carries out fundamental and responsive research on risks and uncertainties in a changing environment.  Our interests include natural hazards, food and energy security, resilience and governance, and human impacts on the environment. Our research fuses rigorous statistical and numerical modelling with a deep understanding of interconnected social, environmental and engineered systems – past, present and future.  We seek to engage wider society – listening to, exploring with, and challenging our stakeholders to develop a shared response to 21st Century challenges.

The European Research Council (ERC)

The main goal of the European Research Council (ERC) is to encourage high quality research in Europe through competitive funding.  It supports investigator-initiated frontier research across all fields of research, on the basis of scientific excellence.  The ERC complements other funding activities in Europe such as those of the national research funding agencies like the Natural Environment Research Council (NERC) in the UK.  From 2010 on, the ERC has a total annual budget of over €1 billion which it uses to fund independent research and training in universities and research centres.