Mount Everest stands 29,032 feet above sea level, hundreds of feet higher than its Himalayan neighbors.
However, geologists believe the world’s tallest mountain is still growing, thanks in part to the confluence of two adjacent river systems tens of thousands of years ago.
Researchers published a study in the journal Nature Geoscience on Monday, attributing an estimated 50 to 160 feet of Everest’s current height to this union. The study also discovered that the yearly rate of growth has accelerated to fractions of a millimeter in recent years.
“Even a feature as seemingly permanent as Mount Everest is subject to ongoing changes driven by various geological forces,” a co-author of the research, Dai Jingen, a geoscientist at China University of Geosciences in Beijing, wrote in an email Tuesday.
The mountain summit, like the rest of the Himalayas, has been continuously rising since its formation around 45 million years ago as a result of the collision of tectonic plates under the Indian subcontinent and Eurasia.
However, this did not completely explain how much Everest was increasing. Researchers say that when the Kosi torrent merged with the Arun River around 89,000 years ago, it created a combined torrent with such enormous force that it destroyed massive amounts of rock and dirt from the Himalayan base approximately 50 miles away from Everest.
In a geological process known as isostatic rebound, erosion reduced the region’s weight, allowing land masses to rise on the Earth’s crust, the outermost layer that floats over a hot, semiliquid rock mantle.
“Essentially, as the river carved away more rocks, the Earth’s crust rebounded, rising like a boat when weight is removed,” said Dai, adding that while the river did not directly cause Everest to rise, the erosion and crust movement it triggered did contribute to the mountain’s height.
Scientists predict that the rebound is causing Everest to rise 0.16 to 0.53 millimeters each year, accounting for up to half of the annual uplift rate. In recent years, they claimed that Everest has grown by up to 2 millimeters per year.
Researchers believe this might explain why Everest is so towering—about 800 feet taller than its neighbors.
The hypothesis that river capture and erosion-related isostatic rebound contribute to Everest’s height, according to Dai, adds a “surprising” dimension to the study of mountain creation, which tectonic activity has generally explained.
“While not entirely revolutionary, these findings are certainly surprising,” Dai stated, adding that they may prompt a rethinking of existing concepts of Himalayan creation and development.
“It also emphasizes the importance of viewing the Earth as an interconnected system, where changes in one area can have surprising and significant impacts elsewhere,” according to him.