The Earth’s crust is a restless body. The massive plates covering the planet’s mantel move a few very measurable inches per year. Why some plates are more slothful than others remains a mystery, but one group of geophysicists has come up with a compelling explanation—the wider the plate, the faster the movement.
Wide plates tend to slip under the adjoining plate more easily than narrower ones, the researchers discovered from their computer simulations. At the boundaries, plates either sink down toward the core or slide into the mantle more or less diagonally. Plates with a wide edge slip sideways more quickly than they sink because the subducted portion of the plate pulls it along. Narrower plates, on the other hand, sink more readily than they slide because friction at the margins of the plate’s edge slow horizontal motion.
Though still a theory, many geophysicists think the new idea holds promise. In an interview with ScienceNOW, Donald Forsyth, a Brown University geophysicist unaffiliated with the study, said, “It’s a nice, really simple concept.”
Image courtesy of NOAA.
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