Decoding the Earth’s chemical secrets reaps rewards

He has not reached the ends of the Earth yet, but Dr John Rudge, a Fellow of Trinity and Lecturer in the Department of Earth Sciences, has been awarded a prestigious prize that will help him and his students continue their journey into the planet’s deep interior.

Dr John Rudge
Dr John Rudge

Dr Rudge, who is trained in mathematics, geophysics and geochemistry, has won the 2015 Philip Leverhulme Prize for Earth Sciences.

His research has changed our understanding of how long it took the Earth to form and how fast material is ‘recycled’ by plate tectonics – the slow movements of the rigid outer shell of our planet.

The world’s 7.3 billion humans live on the relatively thin 40-km crust of the earth, below which lies the mantle, a 3000 km layer of silicate rock that makes up two-thirds of the mass of the planet. Dense iron forms the core of the Earth, which was formed 4.5 billion years ago through collisions of smaller planetary bodies.

Dr Rudge explains:

Much of the early Earth was molten due to the energy released by these collisions, and material of different densities segregated, leading to the layered structure of the Earth we see today. I am interested in understanding the basic physics of these segregation processes, and on placing constraints on their timing.

An artist's impression of planets colliding image © NASA
An artist’s impression of planets colliding image © NASA

Rocks and meteorites contain a record of the Earth’s history, encrypted in chemical codes. By creating mathematical models of the processes that control the chemistry of rocks, Dr Rudge has unlocked some of the planet’s secrets.

Whilst being for the most part solid, the Earth’s mantle slowly creeps on geological time scales due to its high temperature. This mantle convects – the motion of the tectonic plates are a manifestation of this convection. This process also creates mantle plumes – upwellings that bring very hot material from deep down to near the surface, where it melts to form volcanic islands such as Hawaii and Iceland.

Haleakala Crater, Hawaii © John Rudge
Haleakala Crater, Hawaii © John Rudge

Magma, the molten material emitted as lava during a volcanic eruption, offers a unique insight into the planet’s interior and its history. However, Dr Rudge says that decoding its chemical messages is not straightforward.

We cannot directly sample the mantle: we can only sample the lavas which erupt at the surface as a result of mantle melting. To better understand the mantle, we need to better understand the melting process. This is complicated by the fact that lavas are a mixture of a different mantle melts.

A'a Lava Field
Dr Rudge on a lava field, Hawaii

The Leverhulme Prize will allow Dr Rudge to continue his research and enable his PhD students and postdoctoral researchers to participate in fieldwork in volcanic areas, collaborate with their peers at other academic institutions, and work with geologists on the ground and in the laboratory. Dr Rudge said the award was also important for would-be earth scientists at Cambridge:

I will also use part of the prize funds to support summer research projects for undergraduates, nurturing the next generation of earth scientists.

The award recognises the achievement of outstanding researchers whose work has attracted international recognition. Up to 30 prizes of £100,000 each are awarded each year across a range of disciplines.

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