Mount Everest is Earth’s tallest mountain – rising 5.5 miles (8.85 km) above sea level – and is still growing.
While it and the rest of the Himalayas continue to rise, beginning with their birth about 50 million years ago when the Indian subcontinent collided with Eurasia, Everest is rising more than would be expected from this alone. Scientists now think they know the cause, and it has to do with the massive merger of two nearby river systems.
Researchers estimate that Everest’s height increased by approximately 49–164 feet (15–50 m) due to this change in the regional river system, which occurred about 89,000 years ago when the Kosi River merged with the Arun River. This means an uplift rate of about 0.01–0.02 inches (0.2–0.5 millimeters) per year.
The geological process at work is called isostatic rebound, he said. This involves the rising of land mass on the Earth’s crust as the surface mass decreases. The crust, the Earth’s outermost layer, floats above a mantle layer made of essentially hot, semi-liquid rock.
In this case, the merger of the rivers – like a hostile takeover, as the Kosi took over the Arun as the rivers changed course over time – resulted in accelerated erosion that washed away huge amounts of rock and soil, leaving the water Weight was reduced. Area near Everest.
“Isostatic rebound can be compared to a floating object that keeps its position when the weight is removed,” said geologist Jin-Gen Dai of China University of Geosciences in Beijing, one of the leaders of the study published Monday in the journal Nature Geoscience. accommodates.”
Dai said, “When a heavy load such as ice or eroded rock is removed from the Earth’s crust, the ground beneath slowly rises in response, just as a boat rises in water when unloading cargo. “
The main gorge of the merged river system is located about 28 miles (45 km) east of Everest.
The researchers, who used numerical models to simulate the evolution of the river system, estimated that isostatic rebound is about 10% of Everest’s annual uplift rate.
This geological process is not unique to the Himalayas.
“An excellent example is in Scandinavia, where the land is still rising in response to the melting of the thick ice sheets that covered the area during the last ice age. This process continues today, thousands of years after the ice retreated. Beaches and landscapes are being affected,” Dai said.
Adam Smith, co-author of the study and a doctoral student in earth sciences at University College London, said the GPS measurements show the continued rise of Everest and the rest of the Himalaya.
This uplift is in excess of the continuing surface erosion caused by factors such as wind, rain and river flow. As this erosion continues, isostatic rebound could increase Everest’s uplift rate, Smith said.
Neighboring peaks, including Lhotse, the world’s fourth-highest, and Makalu, the fifth-highest, are also fueled by the same process. Lhotse is experiencing a similar rate of uplift as Everest. Makalu, located closer to Uranus, has a slightly higher elevation rate.
Dai said, “This research underscores 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 invisible ways in our daily lives.”
The Earth’s hard exterior is divided into giant plates that move slowly over time in a process called plate tectonics, with the Himalayas rising up after a collision between two plates.
Everest, also known as Sagarmatha in Nepali and Chomolungma in Tibetan, is located on the border between Nepal and China’s Tibet Autonomous Region. It was named after George Everest, a 19th-century British surveyor in India.
“Mount Everest holds a unique place in the human consciousness,” Dai said.
“Physically, it represents the highest point on Earth, which gives it immense importance by virtue of its stature,” Dai said. “Culturally, Everest is sacred to local Sherpa and Tibetan communities. Globally, it symbolizes the ultimate challenge, a symbol of human endurance and our drive to transcend perceived limits.”
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