Earth's billion-year youthful rampage

摘要

Our planet has calmed down in its middle age. Earth was at its most active 1.1 billion years ago, when all the continents collided into one huge supercontinent, and has been getting calmer ever since. It's evidence that the planet has a kind of lifespan. Earth's surface layer, the crust, is divided into tectonic plates that constantly Jostle against each other. When two plates collide, they can be forced up into mountains, or one plate can slide under another and be destroyed. This tectonic activity has been going on for at least 3 billion years, but nobody knows whether Earth has been getting more or less active over time. To find out, Martin Van Kranendonk of the University of New South Wales and Christopher Kirkland of the Geological Survey of Western Australia set out to reconstruct the history of plate tectonics.