There are more than 11,000 cubic miles of magma beneath Yellowstone.
Deep magma reservoirs, such as that below the Yellowstone caldera, are the key to causing volcanic ‘super-eruptions’, that could threaten millions of lives, new research suggests.
If a mega eruption of Yellowstone, one of the world’s largest supervolcanoes, happened so much toxic ash and moult on rock would be hurled into the atmosphere it could block out sunlight and trigger a nuclear-winter type effect or even a mini ice age.
An international team of geologists carried out the study which shows the importance of large magma reservoirs in creating Earth’s most powerful volcanic eruptions.
The researchers claim that the most powerful volcanic eruptions, dubbed ‘super-eruptions’, are triggered by a slow and steady drip feed of magma from large reservoirs deep within the Earth’s crust into smaller reservoirs closer to the surface.
These large reservoirs draw in hot magma from the Earth’s mantle and exist as large volumes of partially molten rock that are able to store magma like a sponge.
The Yellowstone volcano Thu, January 7, 2016
The volcano at Yellowstone National Park in Wyoming and Montana sits atop a huge reserve of magma and last erupted 640,000 years ago
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The Sunset Lake hot spring at Yellowstone National Park, Wyoming
By conducting a number of numerical simulations of this process, the research team showed that these large reservoirs are crucial to generating the largest volcanic eruptions on Earth.
But, fortunately, the team also showed that these large reservoirs can take millions of years to form, hence why ‘super-eruptions’ happen so rarely.
Yellowstone is believed to have seen super eruptions at intervals of two million, 1.2 million and 640,000 years ago, meaning another one could be due any time.
It is believed the new findings could help to understanding why some volcanoes erupt frequently and at certain magnitudes.
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The study, published in the journal Nature Geoscience, found the amount of magma that is stored in the upper layer of the Earth’s crust determines the frequency and magnitude of volcanic eruptions.
Small eruptions that erupt less than one cubic kilometre of material occur very frequently (from daily to yearly), while the largest eruptions that erupt hundreds of cubic kilometres of material are infrequent, with hundreds of thousands of years between them.
Up until now, this theory hasn’t been able to explain how the magma can maintain its heat in these near-surface reservoirs and thus produce extremely powerful eruptions.
Dr Wim Degruyter
Co-author of the study Dr Wim Degruyter, from Cardiff University’s School of Earth and Ocean Sciences, said: “Our current understanding tells us that hot magma can be injected from the Earth’s lower crust into colder surroundings near the surface.
"At this point, the magma can either erupt or cool down to such a point that the magma solidifies and an eruption does not occur.
“Up until now, this theory hasn’t been able to explain how the magma can maintain its heat in these near-surface reservoirs and thus produce extremely powerful eruptions.
“Our study has shown that the key to this is much larger reservoirs deeper below the surface that are able to slowly increase the temperature in the upper part of the crust such that it becomes more amenable to the storage of magma.
"When the crust has become fully mature, giant reservoirs are able to form in the upper crust and thus we see extremely powerful eruptions.”
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In 2010 at least 78 were killed as Mount Merapi erupted in Indonesia
Previous research revealed that a deeper magma body connects to a magma reservoir in the upper part of the crust underneath Yellowstone, which spreads across the sates of Wyoming, Montana and Idaho.
The deeper magma body sits 12 to 28 miles below the surface and it’s believed that the hot molten rock could fill the 1,000-cubic-mile Grand Canyon 11.2 times.
It is believed that the last super eruptions at Yellowstone were fed by the volcanic plumbing system that sits beneath it.
Dr Degruyter added: "Our calculations appear to agree with the observations that have been made at Yellowstone.”
The study, Lifetime and size of shallow magma bodies controlled by crustal-scale magmatism, was led by researchers at ETH Zurich, and also included researchers from the Georgia Institute of Technology.