Due to the erosive forces of the Arun River, Mount Everest grew by 15-50 meters. This erosion causes isostatic rebound, a process in which the Earth’s crust rises due to a decrease in surface mass, causing Mount Everest to rise by about 2 millimeters per year.

Mechanisms to raise Mount Everest

Everest is around 15 to 50 meters (50 to 165 feet) taller than it would normally be due to uplift caused by a nearby eroding river gorge, and so it continues to grow, according to a new study by UCL researchers.

A published study Natural GeologyHe found that erosion of a river network about 75 kilometers (~50 miles) from Mount Everest had cut off an important gorge. The loss of this landmass is causing the mountain to rise by as much as 2 millimeters per year, and has already increased in height by between 15 and 50 meters in the last 89,000 years.

Everest’s abnormal height

Mount Everest, also known as Jomolungma in Tibetan or Sagarmatha in Nepali, is the highest mountain in the world at 8,849 meters, approximately 250 meters higher than the next highest peak in the Himalayas. Everest is thought to be abnormally high for a mountain range, as the next three highest peaks (K2, Kangchenjunga and Lhotse) are only 120 meters apart.

Much of this anomaly can be explained by uplift caused by pressure from beneath the Earth’s crust after a nearby river washed away significant amounts of rock and soil. This is an effect called isostatic recoil; where a section of the crust losing mass bends and “floats” upward because the intense pressure of the liquid mantle below is greater than the downward pull of gravity after mass loss. This is a gradual process, usually just a few millimeters per year, but can significantly change the Earth’s surface over a geological time period.

The constant growth of Mount Everest

Researchers found that thanks to this process, Mount Everest has grown approximately 15 to 50 meters over the past 89,000 years, as the nearby Arun River joins the nearby Kosi River network.

Co-author PhD student Adam Smith (UCL Earth Sciences) said: “Mount Everest is a magnificent mountain of myth and legend and is still growing. “Our study shows that loss of material caused the mountain to rise further as the nearby river system deepened.”

Today the Arun River flows east of Mount Everest and joins the larger Kosi River system downstream. Over thousands of years, the Arun carved a major passage along its banks, carrying away billions of tons of soil and sediment.

Co-author Dr. from China University of Geosciences. Jin-Gen Dai said: “There is an interesting river system in the Everest region. The upper reaches of the Arun River flow eastward at high altitude with a flat valley. It then makes a sharp turn to the south in the form of the Kosi River, which decreases in height and becomes steeper. It is an unstable river.” “This unique topography is probably related to Everest’s extreme height.”

Regional influence beyond Everest

The rise is not limited to Mount Everest, but is also affecting nearby peaks, including Lhotse and Makala, the fourth and fifth highest peaks in the world. Isostatic rebound increases the height of these peaks by the same amount as Mount Everest, although Makalu, located closest to the Arun River, experiences a slightly higher rate of ascent.

Co-author Dr. Matthew Fox (UCL Earth Sciences) said: “Mount Everest and nearby peaks are growing because isostatic rebound lifts them faster than erosion wears them down. With GPS devices we can see them growing by around two millimeters per year and we now have a better understanding of what is causing this.”

Insights into the dynamics of the Himalayas’ rise

By looking at the erosion rates of the Arun, Kosi and other rivers in the region, researchers were able to determine that the Arun River joined the Kosi River network about 89,000 years ago through a process called drainage piracy. At the same time, more water passed through the Kosi River, increasing its erosive power and taking with it more soil and landscape sediments. The drifting away of much of the land increased the rate of uplift and pushed the mountain tops higher and higher.

Lead author Dr. from China University of Geosciences, who conducted the study during the China Scholarship Council’s research visit to UCL. Xu Han said: “The change in the height of Mount Everest really highlights the dynamic nature of the Earth’s surface. The interaction between the erosion of the Arun River and the upward pressure of the Earth’s mantle is accelerating Mount Everest, pushing it higher than it would otherwise be.” .”