Mount Everest is growing more than expected – 10/01/2024 – Science

The highest mountain on Earth, at 8.85 kilometers above sea level, Mount Everest is still growing.

Although the mountain and the rest of the Himalayas have seen an inexorable rise dating back to the emergence of both about 50 million years ago, when the Indian subcontinent collided with Eurasia, Everest is growing larger than expected. And this, according to scientists, is related to the merger of two river systems.

Everest gained approximately 15 to 50 meters in height due to a change in the regional river system, with the Kosi River merging with the Arun River 89,000 years ago, researchers estimate. This translates into a rise rate of 0.2 to 0.5 millimeters per year.

The geological process at work, according to the researchers, is called isostatic rebound. It involves the lifting of land masses in the Earth’s crust when the weight of the surface decreases. The crust, Earth’s outermost layer, essentially floats on top of a mantle layer made of hot, semi-liquid rock.

In this case, the merging of the rivers — more like a hostile takeover, with the Kosi overwhelming the Arun as the rivers changed course over time — resulted in accelerated erosion that carried away large quantities of rock and soil, reducing the region’s weight. near Everest.

“Isostatic rebound can be compared to a floating object adjusting its position when weight is removed,” said geoscientist Jin-Gen Dai of China University of Geosciences in Beijing, one of the leaders of the study published on Monday (30 ) in the journal Nature Geoscience.

“When a heavy load, such as ice or eroded rock, is removed from the Earth’s crust, the land below slowly rises in response, just like a boat rising in the water when the load is unloaded,” Dai said.

The main gorge of the merged river system is located approximately 45 km east of Everest.

The researchers used numerical models to simulate the evolution of the river system. They calculated that isostatic rebound represents about 10% of Everest’s annual rate of elevation.

This geological process is not exclusive to the Himalayas.

“A classic example is in Scandinavia, where the land is still rising in response to the melting of thick sheets of ice that covered the region during the last Ice Age. This process continues today, affecting coastlines and landscapes, thousands of years after ice retreat,” Dai said.

Study co-author Adam Smith, a PhD student in Earth Sciences at University College London, said GPS measurements show the continued rise of Everest and the rest of the Himalayas.

This survey overcomes the continuous surface erosion caused by factors such as wind, rain and river flow. As this erosion continues, the rate of Everest’s rise from isostatic rebound could increase, Smith said.

Neighboring peaks, including Lhotse, the fourth highest in the world, and Makalu, the fifth highest, also receive a boost from the same process. Lhotse is experiencing a similar rate of elevation to Everest. Makalu, closer to Arun, has a slightly higher elevation rate.

“This research highlights the dynamic nature of our planet. Even a seemingly immutable feature like Mount Everest is subject to ongoing geological processes, reminding us that the Earth is constantly changing, often in ways imperceptible in our daily lives,” said Dai .

The hard outer part of the Earth is divided into colossal plates that gradually move over time in a process called plate tectonics, with the Himalayas rising after a collision between two plates.

Everest is located on the border between Nepal and Tibet. It was named after British surveyor George Everest (1790-1866).

“Mount Everest occupies a unique place in human consciousness,” Dai said. “Physically, it represents the highest point on Earth, giving it immense importance simply by its stature. Culturally, it is sacred to the local Sherpa and Tibetan communities. And globally, it symbolizes the ultimate challenge, embodying human endurance and our willingness to overcome perceived limits.”