Scientists Unravel Why Everest Keeps Growing

Scientists and those adept at trivia contests can tell you that Mount Everest stands at 29,032 feet. Give it enough time, however, and that answer will tick higher, and a new study in Nature Geoscience sheds new insight into why, reports the Guardian. It has to do with the merging of two ancient rivers, and the ecological chain reaction that continues to this day.

• Everest formed 40 to 50 million years ago when two tectonic plates crashed into each other. The peak would be expected to rise 1 millimeter (.04 inches) per year thanks to slow-moving shifting still underway, but Everest actually rises twice that amount, reports CNN.
• The new study chalks that up to something known as "river piracy." About 89,000 years ago, the larger Kosi River absorbed the smaller Arun River, and the enlarged new river began chewing up the landscape around Everest with ferocity, per the New York Times.

• This erosion stripped away sediment and bedrock in the region, reducing the weight on the Earth's crust. In a process known as "isostatic rebound," other parts of the land were uplifted. "It's like the landscape was doing the limbo—lower in some places, higher in others," study co-author Jin-Gen Dai of China University of Geosciences in Beijing tells CNN.
• Researchers estimate that Everest has thus had a "growth spurt" of an extra 15 to 50 meters (roughly 50 to 165 feet) since the two rivers merged. "Although mountains may appear to stand still from the perspective of a human lifetime, they are in fact constantly in motion," says the geoscientist, per the Times.

(More Mount Everest stories.)