Mount Everest Keeps Growing—a New Study May Help Explain Why

The tallest mountain on Earth keeps getting taller.

You might think Mount Everest, nature’s most imposing skyscraper, would shrink by a few millimeters each year due to erosion or other factors. Instead, it continues growing in height, and science now has a better understanding of why.

In a paper published in the journal Nature Geoscience, a team of researchers from London and Beijing suggest that erosion is in play—but it’s actually to the mountain’s benefit. Erosion at the point where the Arun and Kosi rivers meet, 47 miles away from Everest, continually and steadily eats away the rock. Over tens of thousands of years, the decrease in rock weighing down Earth's surface has allowed it to rise, a phenomenon known as isostatic rebound. As the Earth’s crust gets lighter, it’s able to “float” over the mantle, rising and pushing Everest skyward.

As such, the Himalayas are metaphorically resting “on a bouncy castle,” Adam Smith, a co-author of the paper, told The New York Times.

Using computer modeling, researchers estimate Everest grows about 2 millimeters annually. That could add up to anywhere from 50 to 165 extra feet since the Arun and Kosi rivers merged roughly 89,000 years ago—though Everest has likely always been slowly rising. The process can outpace whatever erosion might have otherwise brought it down.

“An interesting river system exists in the Everest region,” co-author Dr. Jin-Gen Dai said in a statement. “The upstream Arun river flows east at high altitude with a flat valley. It then abruptly turns south as the Kosi river, dropping in elevation and becoming steeper. This unique topography, indicative of an unsteady state, likely relates to Everest's extreme height.”

The effect can also be seen in the nearby Lhotse and Makalu peaks, which are among the highest in the world.

Currently, Everest maxes out at 29,032 feet above sea level, thought that was settled only after years of bickering. Nepal once put it at 29,029 feet, while China believed it was 29,015 feet after subtracting the snow layer.

Contrary to popular perception, Everest’s reputation as being the tallest mountain in the world can get bogged down in semantics. Mauna Kea in Hawaii, for example, stretches to 30,610 feet, but most of it is below sea level.

Other experts have praised the new study, but caution that the cumulative effect of river erosion can be difficult to measure. It’s also likely not the sole cause of the mountain’s continued ascension.

It’s possible that one day the isostatic rebound may cease, and Everest could even begin to sink. But for now, one of the great wonders of the world doesn’t appear to be done growing.

Read More About Mount Everest: