Why are Earth's continents suddenly moving? Thick 'crusts' and minerals are behind mystery changes, claims study
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Scientists claim they have answered one of the biggest questions in geology; why do tectonic plates beneath the Earth's surface sometimes move abruptly?
In a new study, US geologists believe the answer comes down to a combination of the thick crusts and weakened mineral grains.
Those effects acting together, they say, could explain a range of relatively 'speedy' moves among tectonic plates around the world, from Hawaii to East Timor.
Traditionally, scientists believed that all tectonic plates are pulled by subducting slabs - which result from the colder, top boundary layer of the Earth's rocky surface becoming heavy and sinking slowly into the deeper mantle. Pictured is a diagram of a coastal area where an ocean plate is subducting beneath a continental plate
'Our planet is probably most distinctly marked by the fact that it has plate tectonics,' said Yale University geophysicist David Bercovici, lead author of the research.
'Our work here looks at the evolution of plate tectonics. How and why do plates change directions over time?'
Traditionally, scientists believed that all tectonic plates are pulled by subducting slabs - which result from the colder, top boundary layer of the Earth's rocky surface becoming heavy and sinking slowly into the deeper mantle.
Yet that process does not account for sudden plate shifts – which in geological terms is still a million years or longer.
Thick crust from continents or oceanic plateaux is swept into the subduction zone prompting the slab to break off. The result is tectonic plates that abruptly shift horizontally, or continents suddenly bobbing up
Such abrupt movement requires that slabs detach from their plates, but doing this quickly is difficult since the slabs should be too cold and stiff to detach.
According to the Yale study, there are additional factors at work.
Thick crust from continents or oceanic plateaux is swept into the subduction zone, plugging it up and prompting the slab to break off.
The detachment process is then accelerated when mineral grains in the necking slab start to shrink, causing the slab to weaken rapidly.
The result is tectonic plates that abruptly shift horizontally, or continents suddenly bobbing up.
'Understanding this helps us understand how the tectonic plates change through the Earth's history,' Professor Bercovici said.
'It adds to our knowledge of the evolution of our planet, including its climate and biosphere.'
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