Everest has grown in height: the tallest mountain in the world has become even taller

Climbing Everest has always been a feat, but the task appears to be getting harder: Researchers say Everest is going through something of a growth spurt, The Guardian writes.

The Himalayas were formed about 50 million years ago when the Indian subcontinent crashed into the Eurasian tectonic plate, although recent research has shown that the edges of these plates were already very high before the collision.

Because this process is still ongoing, the mountain range continues to rise, although landslides and other events also cause rock loss.

But experts now say Everest, which currently stands at 8,849m (29,032ft), is experiencing additional rise as a result of erosion caused by nearby rivers.

The team says this process has caused Everest to rise another 15 to 50 meters over the past 89,000 years, and the rise continues to this day.

“Our study shows that even the world's highest peak is subject to constant geological processes that can markedly affect its height over relatively short geological periods of time,” said Professor Jinggen Dai, co-author of the study from China University of Geosciences in Beijing.

Professor Dai notes that Everest is something of an anomaly because its peak is about 250 meters higher than the other highest mountains in the Himalayas. In addition, the data suggests a discrepancy between the long-term and short-term rates of Everest's rise.

“This raised the question of whether there is an underlying mechanism that makes Everest's abnormal height even higher,” Dai emphasizes.

In a paper published in the journal Nature Geoscience, Dai and his colleagues report how they created computer models to study the evolution of river networks in the Himalayas.

Their results suggest that about 89,000 years ago, the upper course of the Arun River, which flows north of Everest and would have flowed east across the Tibetan Plateau, merged with its lower course as a result of the latter being eroded in a northerly direction. As a result, the entire length of the Arun River became part of the Kosi river system.

The researchers suggest that the rerouting as a result of this “river capture” led to increased river erosion in the Everest region and the formation of the Arun River Gorge.

“At that time, there would have been a huge amount of extra water flowing through the River Arun and this could have carried more sediment, eroded more bedrock and deepened the valley floor,” said Dr Matthew Fox, co-author of the study from University College London.

The researchers say the loss of crustal weight as this material was removed caused the surrounding land to rise, a process known as isostatic rebound.

The team estimates that this process is causing Everest to rise by about 0.16-0.53 mm per year, and its neighbors Lhotse and Makalu, the world's fourth and fifth highest peaks respectively, are experiencing similar rises.

“This effect will not continue indefinitely,” says Professor Dai. “The process will continue until the river system reaches a new equilibrium state.”

Professor Mikael Attal from the University of Edinburgh, who was not involved in the work, said that while river capture was a well-known phenomenon, it was relatively rare.

“What is unique about this study is the demonstration that erosion resulting from river capture can lead to such a dramatic change in the earth's surface, with an area the size of Greater London increasing by tens of meters over tens of thousands of years, which happens very quickly “, he said.

However, Attal notes that this jump only partly explains the unusual height of the highest peaks of the Himalayas. Indeed, Fox noted that other mechanisms, such as tectonic stresses associated with earthquake cycles and the loss of mountain glaciers, can also cause uplift.

Dr Elizabeth Dingle, from Durham University, said the study's findings could have implications beyond Everest.

“Other river entrainments are known to have occurred in the Himalayas,” she said, “so it would be interesting to see whether similar effects persist elsewhere, or in other tectonically active mountain ranges more broadly.”