Plate tectonics may have begun a billion years earlier than thought

By Michael Marshall

Plate tectonics may have begun 4 billion years ago, almost a billion years earlier than we thought, according to a new analysis of ancient rocks.

The claim has earned a mixed response from geologists. Many argue that Earth was too hot at the time for plate tectonics in its modern form.

Today, Earth’s crust is divided into several dozen rigid plates, which move around over millions of years. Where two plates meet, one can be forced under the other and destroyed inside the planet, a …