New study has increased our knowledge of volcanic eruptions by connecting eruption size and frequency to the speed at which magma forms in deep underground reservoirs. These results could improve predictions and protect communities. (Artist’s concept.) Credit: SciTechDaily.com
Recent research on liquid rock 20km beneath the Earth’s surface might improve the forecasting of volcanic activity, potentially saving lives.
Volcanic eruptions are highly dangerous and have severe impacts on both nearby residents and the environment.
Currently, predictions of eruptions are based on volcano activity and the upper few kilometers of crust containing molten rock that could erupt.
Nevertheless, new research emphasizes the importance of looking for clues deeper in the Earth’s crust, where rocks are transformed into magma before moving towards the surface chambers.
In order to comprehend the internal processes of the planet's most explosive events, experts at Imperial College London and the University of Bristol delved into the frequency, composition, and scale of volcanic eruptions worldwide.
Their findings indicate that the frequency and size of eruptions are closely tied to the duration it takes for extremely hot, liquid rock, known as magma, to form in these deep reservoirs underneath the Earth’s crust – at depths of up to 20 kilometers – as well as the size of these reservoirs.
Researchers believe that the findings, published today (May 10) in the journal Science Advances, will enable more accurate predictions of volcanic eruptions, ultimately safeguarding communities and mitigating environmental risks.
Studying Volcanoes Around the World
The study, led by researchers at the Department of Earth Science and Engineering at Imperial, reviewed data from 60 of the most explosive volcanic eruptions, spanning nine countries: the United States, New Zealand, Japan, Russia, Argentina, Chile, Nicaragua, El Salvador, and Indonesia.
Study author Dr. Catherine Booth, Research Associate in the Department of Earth Science and Engineering at Imperial College London, said: “We looked at volcanoes around the world and dug deeper than previous studies that focused on shallow underground chambers where magma is stored before eruptions. We focused on understanding magma source reservoirs deep beneath our feet, where extreme heat melts solid rocks into magma at depths of around 10 to 20 kilometers.”
The team combined real-world data with advanced computer models. They looked at the composition, structure, and history of rocks deep beneath the Earth’s crust, alongside information gathered from active volcanoes, to understand how magma builds up and behaves deep underground, eventually rising through the Earth’s crust to volcanoes.
Using this information, researchers created computer simulations that mimic the complex processes of magma flow and storage deep within the Earth. Through these simulations, the team gained new insights into what factors drive volcanic eruptions.
Identifying Key Controls of Eruptions
“Our study suggests that the buoyancy of the magma, rather than the proportion of solid and molten rock, is what causes eruptions,” Dr. Booth stated.
“The buoyancy of magma is determined by its temperature and chemical makeup compared to the surrounding rock – as the magma accumulates, its composition changes to make it less dense, allowing it to rise.
“Once the magma becomes buoyant enough to float, it rises and creates fractures in the overlying solid rock – then it flows through these fractures very rapidly, causing an eruption.”
In addition to identifying magma buoyancy as a significant factor driving eruptions, researchers also examined how magma behaves when it reaches shallower underground chambers just before erupting. They discovered that how long magma was stored in these shallower chambers can also impact volcanic eruptions, with longer storage periods leading to smaller eruptions.
While larger reservoirs might be expected to fuel larger, more explosive eruptions, the findings also revealed that very large reservoirs disperse heat, which slows down the process of melting solid rocks into magma. This led researchers to conclude that the size of reservoirs is another crucial factor for accurately predicting eruption sizes – and that there is an optimal size for the most explosive eruptions.
The research also highlights that eruptions are seldom isolated and, instead, are part of a recurring cycle. Additionally, the magma released by the volcanoes they studied was high in silica, a natural compound known to play a role in determining the thickness and explosiveness of magma – with high-silica magma tending to be more viscous and resulting in more explosive eruptions.
Next Steps
Co-author Professor Matt Jackson of the Department of Earth Science and Engineering at Imperial College London noted: “By enhancing our understanding of the processes behind volcanic activity and providing models that illuminate the factors controlling eruptions, our study is a crucial step towards better monitoring and forecasting of these powerful geological events.
“Our study had some limitations: our model focused on how magma flows upwards, and the source reservoirs in our model contained only molten rock and crystals. However, there is evidence that other fluids such as water and carbon dioxide are also found in these source reservoirs, and that magma can swirl and flow sideways.”
The next steps for researchers will involve refining their models, integrating three-dimensional flow, and considering different fluid compositions. By doing so, they aim to continue decoding the Earth’s processes responsible for volcanic eruptions – in turn, aiding in better preparation for natural disasters in the future.
Reference: “Source reservoir controls on the size, frequency and composition of large-scale volcanic eruptions” 10 May 2024, Science Advances.
DOI: 10.1126/sciadv.add1595
