Mantle plume may have started tectonic activity

Science : When Earth was forming, its crust was an unbroken sphere. Today, the crust is fractured all over, and the different plates move because of pressures at subduction zones. How the crust changed is uncertain; common suggestions include meteorite impacts and the convection of the mantle. Now, Scott Whattam of Korea University in Seoul, Robert Stern of the University of Texas at Dallas, and Taras Gerya of ETH-Zürich in Switzerland have suggested that an exceptionally hot mantle plume could have kicked things off. Whattam and Stern had previously studied an extremely hot plume that appears to have triggered subduction along the Caribbean coasts of Central and South America 100 million years ago. With Gerya, they created a three-dimensional model showing that as magma from a plume rises to the surface and erupts, it creates a buoyant plateau of crust. The magma then weakens the plateau, which causes it to collapse, and pieces of the plateau push the surrounding lithosphere downward into a funnel shape. Over time that area of lithosphere weakens and fractures; the pieces sink into the mantle and begin the subduction process.