Stop-and-go plate tectonics
Plate tectonics might have gotten a fitful start on the early Earth. Today, the process of Earth’s crustal movement called plate tectonics dictates nearly everything about the planet’s appearance, from the sites and heights of the mightiest mountain ranges to the depths of the oceans’ trenches. But geologists have long argued about when thin, rigid crustal plates first formed on the young planet and began jostling against one another. Now, two researchers propose that plate tectonics started and stopped over and over, billions of years ago, before running continuously.
In the graphic above, a simulation of plate tectonics today (left) shows a crustal slab (green) plunging more than 400 kilometers into Earth’s mantle. Billions of years ago (right), when the mantle was 200 degrees Celsius hotter, the slab would have barely penetrated the depths before breaking off and foundering. Geologists propose this difference led to intermittent plate tectonic activity early in Earth’s history.
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