Mount Everest, known as the world’s highest peak, has begun to grow further due to erosion by nearby rivers, according to a new study that highlights the complex geological processes that influence its height.
Mount Everest has an “impulse” to grow, say researchers PHOTO Archive
The Himalayas were formed about 50 million years ago when the Indian subcontinent collided with the Eurasian tectonic plate – although recent research suggests that the edges of these plates were already very high before the collision, writes The Guardian.
The process continues and the mountain range is pushed up, although landslides and other events mean that rock is also lost.
But experts now say that Everest – which currently stands at 8,849m – has experienced a further boost in height as a result of erosion by neighboring rivers.
The team says this process has caused Everest to rise 15 to 50 meters over the past 89,000 years, and the rise continues today.
Geological anomalies and mechanisms
“Our study demonstrates that even the world’s tallest peak is subject to ongoing geological processes that can measurably affect its height over relatively short geological scales”said Prof. Jingen Dai, co-author of the study from the China University of Geosciences in Beijing.
Dai pointed out that Everest is something special, with its peak located about 250 meters higher than other highest peaks of the Himalayas. Furthermore, the data suggest a discrepancy between the long-term and short-term rates of rise of Everest.
“This raised the question of whether there was an underlying mechanism that made Everest’s anomalous height even greater,” Dai said.
In the journal Nature Geoscience, Dai and his colleagues report how they created computer models to explore the evolution of Himalayan river networks.
Their results suggest that 89,000 years ago, the upper course of the Arun River, which lies north of Everest – and would flow eastwards on the Tibetan Plateau – merged with its lower course as the latter eroded northwards . The result was that the entire length of the Arun River became part of the Kosi River system.
The team suggests that the redirection resulting from this “river catch” led to increased river erosion near Everest and the formation of the Arun River Canyon.
“At that time there would have been a huge amount of extra water flowing through the River Arun and that could have carried more sediment and eroded more bedrock and cut deep into the valley floor.”said Dr Matthew Fox, co-author of the research from University College London.
Elevation of the land
The researchers say that the weight reduction on Earth’s crust as this material was removed caused the surrounding land to rise – a process known as isostatic rebound.
The team estimates that this process pushes Everest up by about 0.16 mm to 0.53 mm per year, with its neighboring peaks, Lhotse and Makalu, the world’s highest peaks, experiencing similar uplift.
“This effect will not continue indefinitely”Dai said. “The process will continue until the river system reaches a new equilibrium state.”
Prof Mikaël Attal of the University of Edinburgh, who was not involved in the work, said that although river capture is a well-known phenomenon, it is relatively rare.
“What is unique about this study is the demonstration that erosion from river catchment can lead to such a dramatic response of the Earth’s surface, with an area the size of Greater London rising by tens of meters in tens of thousands of years , which is fast”he said.
However, Attal notes that this rebound explains only a fraction of the unusual height of the Himalaya’s highest peaks. In fact, Fox pointed out that other mechanisms, such as tectonic stresses associated with earthquake cycles and the loss of mountain glaciers, could also be causing the uplift.
Dr Elizabeth Dingle from Durham University said the study’s findings could be important beyond Everest.
“There are other river captures known to have occurred in the Himalayas”she said, “so it would be interesting to know if similar effects hold in other tectonically active mountain ranges in general.”
