Earth and Environmental Sciences (SEES)
Minerals hold key to unlocking Earth's past
Tue, 25 Oct 2011 09:56:00 BST
Scientists at the University of Portsmouth have won a £400,000 grant to try and find out when Earth’s surface started moving.
Many scientists believe the way that the Earth’s crust is moving and pushing the continents apart changed around 700 million years ago. But Dr Craig Storey and Dr Mike Fowler believe that the evidence for this is not reliable. They believe that this style of movement could have begun hundreds of millions of years earlier and if they are right, the models showing how the planet has evolved will need to be rewritten.
The project leader, Dr Storey, said: “The continents we have now were once one supercontinent, a single land mass, which has broken up and reformed many times since Earth was formed.
“Tectonic plate movement, responsible for earthquakes and volcanoes around the globe, is difficult to measure if you want to look back hundreds of millions of years. But we think we might have found the key to unlocking the story of when the planet has changed in two minerals, rutile and zircon.”
He and colleagues in the university’s School of Earth and Environmental Sciences will spend three years examining deposits of these minerals to pinpoint where an oceanic plate has collided with a continental plate in the past. Rocks formed at the same time have been lost to erosion over hundreds of millions of years, but certain minerals have survived the erosion and end up buried in sediments.
Dr Storey said: “When an oceanic plate collides with a continental plate the forces are so peculiar to that location, a rock called blueschist is formed which contains rutile. It is a brilliant blue and can be seen on the Greek island of Syros. Blueschist is one of the fingerprints of modern plate tectonics and tells a story of the violence and dynamism of the earth’s crust movement that is undeniable.
“Volcanoes are also formed when oceanic and continental plates collide and the rocks produced in them contain zircon.
“Using our new methods, rutile and zircon can be used to provide reliable diagnostic evidence that the plates moved in a certain dramatic way much earlier than in just the last 700 million years.”
If modern plate tectonics is found to have started earlier than 700 million years ago, science’s understanding of how fast Earth has cooled and evolved would undergo a major tectonic shift of its own. Dr Storey said: “Such a result would be surprising for a large number of geologists.”
The grant was awarded by the Natural Environment Research Council (NERC) and will fund a postdoctoral research assistant and a PhD student. Dr Storey and his team expect to report their findings in 2015.