Advanced computer simulations shed new light on magma deep below Earth’s surface

Carla Rosario, Computer Science, Second Year

What exactly is happening beneath our feet, in the Earth’s core, is one of man’s most enduring mysteries. A novel University of Bristol led study sheds a rare new light on the topic.

It’s bad news for Total Recall fans - travelling through the earth’s core isn’t happening anytime soon. However, using advanced computer simulations, researchers from Bristol have unveiled new properties of the magmas in the mantle.

The study, funded by the UK Natural Environment Research Council, has taken three years and was part of a collaborative effort by physicists and Earth scientists from universities in the UK, US and China.

Whilst you most likely know about the ‘water cycle’ we are taught in school, the ‘deep water cycle’ is a much more mysterious process. It refers to the exchange of water with the mantle at subducting oceanic plate boundaries in the deep ocean, and is ‘tightly connected to Earth’s habitability’. This is a major topic of interest for humanity.

Lead author Dr James Drewitt, who is a Senior Research associate at the University of Bristol, was not convinced by previous theories that these water-rich molten rocks would be denser than the solid rock above them.

In Drewitt’s words, these theories relied on ‘chemical compositions which are unrepresentative of natural magmas, as known from high-pressure laboratory experiments’. He saw that more accurate detail about the properties of hydrous magmas, could reveal better insight into their movements.

The researchers turned to ARCHER, the UK's national supercomputing service

However, it is difficult to disprove theories like these when humans cannot travel farther than a few kilometres into the earth’s core. So rather than start digging, the researchers turned to ARCHER, the UK’s national supercomputing service, to run complex models simulating the physical properties of the mantle. For the first time, this allowed them to ‘model hydrous magmas down to the atomic scale’.

The study found that the magmas are much more buoyant and fluid than previously assumed and must therefore ‘rise through the upper-mantle towards the surface, like the wax rising in a lava lamp’. These new properties were incorporated into global mantle circulation models, which revealed that over geological timescales, water in hydrous magmas was transported towards the upper mantle. This resulted in a similar mass of water found in all Earth’s oceans being ‘evenly distributed throughout the mantle of present-day Earth’.

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The findings from this new study will therefore allow researchers to better track the movement of these water-rich magmas, which in turn influences Earth’s deep-water cycle.

Featured Image: Unsplash/Pawel Czerwinski

How much did you know about the earth's deep-water cycle?