Mount Everest, the world’s highest peak, may be 15 to 50 meters taller than previously estimated due to erosion caused by a river at its base, according to a groundbreaking study from University College London (UCL). Researchers found that the Arun River, located approximately 75 kilometers away, is contributing to Everest’s rise by eroding rock and soil, enabling the mountain to ascend by up to 2 millimeters annually.
Study co-author Adam Smith likened the process to a ship losing cargo, causing it to float higher. “When the crust becomes lighter, it can float a little higher,” he explained to the BBC. The Himalayas were formed by the collision of the Indian and Eurasian tectonic plates 40 to 50 million years ago, a process that continues to influence their elevation. However, the UCL team suggests that the erosion caused by the Arun River is playing a significant role in this geological phenomenon.
As the Arun flows through the Himalayas, it carves away material from the Earth’s crust, alleviating pressure on the underlying mantle. This reduction in pressure causes the crust to flex and rise, a process known as isostatic rebound. According to the study, this upward force is not only elevating Everest but also neighboring peaks like Lhotse and Makalu, the fourth and fifth highest mountains in the world.
Dr. Matthew Fox, another co-author of the study, stated, “Mount Everest and its neighboring peaks are growing because the isostatic rebound is raising them up faster than erosion is wearing them down.” Using GPS technology, researchers have documented the mountains’ growth, estimating an upward movement of approximately 2 millimeters per year.
While some geologists find the theory plausible, they caution that many aspects of the research remain uncertain. The Arun River, which flows from Tibet into Nepal before merging with other rivers to form the Kosi, is particularly effective at erosion due to its steep terrain and high silt yield. UCL researchers believe the river gained its significant erosive power after it captured another river or water body in Tibet around 89,000 years ago—a relatively recent event in geological terms.
Dr. Xu Han of China University of Geosciences, the study’s lead author, highlighted the dynamic nature of Earth’s surface. “The interaction between the erosion of the Arun River and the upward pressure of the Earth’s mantle gives Mount Everest a boost, pushing it up higher than it would otherwise be,” he noted.
However, uncertainties about the exact amounts and timescales of river incision and the resulting uplift of surrounding peaks were acknowledged by the authors. Professor Hugh Sinclair from the University of Edinburgh emphasized the challenges of predicting river erosion over large areas and the complexities involved in understanding the impacts of localized erosion on mountain elevation. Nevertheless, he stated that the link between Everest’s height and the Arun River represents an exciting insight into geological processes.
