Mount Everest has gained an extra height of approximately 15 to 50 meters due to the uplift triggered by a nearby eroding river gorge, and ongoing research indicates this growth is still happening.
A recent study published in Nature Geoscience reveals that the erosion from a river system located about 75 kilometers away from Mount Everest is significantly deepening a gorge. This erosion results in the mountain rising by as much as 2 millimeters annually, leading to a cumulative height increase of 15 to 50 meters over the last 89,000 years.
Standing at 8,849 meters, Mount Everest, also referred to as Chomolungma in Tibetan and Sagarmāthā in Nepali, holds the title of the tallest mountain on the planet, towering approximately 250 meters above the next highest Himalayan peak. Its exceptional height is notable, especially when compared to the next three tallest mountains—K2, Kangchenjunga, and Lhotse—which are only about 120 meters apart in height.
This unusual elevation can largely be attributed to an uplifting force originating from beneath the Earth’s crust, influenced by the erosion of nearby rocks and soil by a river. This phenomenon is known as isostatic rebound, where a section of the Earth’s crust that has lost mass rises due to the pressure from the liquid mantle underneath being greater than the gravitational force acting downward. Although this is a slow process—usually just a few millimeters each year—it can result in significant changes to the landscape over long periods.
The researchers noted that Mount Everest’s height has increased between 15 and 50 meters in the last 89,000 years following the time when the Arun river merged with the adjacent Kosi river network.
PhD student Adam Smith from UCL Earth Sciences, a co-author of the study, remarked: “Mount Everest stands as a fascinating mountain steeped in myth, and it continues to rise. Our findings indicate that as the river system erodes deeper, the resulting loss of material is propelling the mountain even higher.”
Currently, the Arun river flows to the east of Mount Everest and joins the larger Kosi river further downstream. Over thousands of years, the Arun river has created a deep gorge, removing billions of tonnes of earth and sediment from the area.
Dr. Jin-Gen Dai from the China University of Geosciences, another co-author, noted: “In the Everest region, there exists a captivating river system. The Arun river, which flows east at a high altitude through a flat valley, suddenly shifts southward as the Kosi river, decreasing in height and becoming steeper. This distinctive topography, pointing to an unstable state, likely contributes to Everest’s remarkable height.”
The uplift effect is not confined to Mount Everest alone and impacts neighboring peaks, such as Lhotse and Makalu, which rank as the fourth and fifth tallest mountains in the world, respectively. The force of isostatic rebound elevates these peaks similarly to Everest, with Makalu—closest to the Arun river—experiencing a slightly greater uplift rate.
Dr. Matthew Fox from UCL Earth Sciences explained: “The growth of Mount Everest and nearby mountains is due to isostatic rebound lifting them faster than erosion is wearing them down. Using GPS instruments, we can observe this increase of about two millimeters per year, and now we have a clearer understanding of the factors driving this change.”
By examining the erosion rates of the Arun, the Kosi, and other nearby rivers, the researchers discovered that around 89,000 years ago, the Arun river merged into the Kosi river network, a process known as drainage piracy. This event allowed more water to flow through the Kosi, enhancing its erosion capabilities and carrying away more soil and sediment. As more land was eroded, it led to an accelerated uplift, elevating the mountain peaks even further.
Lead author Dr. Xu Han from the China University of Geosciences, who conducted this research during a visit to UCL, stated: “The changing altitude of Mount Everest serves as a powerful reminder of the Earth’s dynamic surface. The interplay between the Arun river’s erosion and the upward pressure from the Earth’s mantle is giving Everest an extra lift, making it even taller than it would be otherwise.”
