MAHALANGUR HIMAL — Mount Everest, the highest mountain on Earth at 5.5 miles (8.85 km) above sea level, is still growing. This growth is part of a larger process that began about 50 million years ago when the Indian subcontinent collided with Eurasia. Recent research suggests that Everest is increasing in height more than previously anticipated due to the merger of two nearby river systems.

Estimates indicate that Everest has risen between 49 to 164 feet (15 to 50 meters) as a result of this river merger, which occurred approximately 89,000 years ago when the Kosi River combined with the Arun River. This translates to an uplift rate of around 0.01 to 0.02 inches (0.2 to 0.5 millimeters) per year.

The geological phenomenon responsible for this is called isostatic rebound. This process occurs when land masses rise on the Earth's crust as the weight on the surface decreases. The Earth's crust, which is the outer layer, floats atop a semi-liquid mantle.

In this instance, the Kosi River's dominance over the Arun River led to increased erosion, removing vast amounts of rock and soil and thereby lightening the load on the region surrounding Everest. Geoscientist Jingen Dai from the China University of Geosciences in Beijing, who co-led the study published on September 30 in Nature Geoscience, explained, "Isostatic rebound is similar to a floating object adjusting its position when weight is taken off."

"When a heavy burden, like ice or eroded rock, is removed, the land beneath gradually rises, akin to a boat rising in water when cargo is unloaded," Dai added.

The primary gorge of this merged river system is located about 28 miles east of Everest. Researchers utilized numerical models to simulate the river system's evolution and concluded that isostatic rebound contributes roughly 10% to Everest's annual uplift rate.

This geological process is not exclusive to the Himalayas. "A classic example can be seen in Scandinavia, where the land is still rising due to the melting of thick ice sheets from the last Ice Age, which continues to affect coastlines and landscapes even thousands of years after the ice has receded," Dai noted.

Study co-author Adam Smith, a doctoral student in Earth sciences at University College London, indicated that GPS measurements confirm Everest's continued rise alongside the Himalayas. This uplift is greater than the erosion caused by elements such as wind, rain, and river flow. Smith added that as erosion continues, the uplift rate due to isostatic rebound may increase.

Nearby peaks, including Lhotse, the world's fourth highest, and Makalu, the fifth highest, are also benefiting from this process. Lhotse is rising at a rate comparable to Everest, while Makalu, closer to the Arun, experiences a slightly higher uplift rate.

"This research highlights the dynamic nature of our planet. Even a seemingly unchanging feature like Mount Everest is subject to ongoing geological changes, reminding us that Earth is always evolving, often in ways that are not noticeable in our daily lives," Dai stated.

The Earth's rigid outer layer consists of massive plates that gradually move over time, a process known as plate tectonics. The Himalayas have risen as a result of the collision between two tectonic plates.

Everest, also referred to as Sagarmatha in Nepali and Chomolungma in Tibetan, lies on the border between Nepal and China's Tibet Autonomous Region. It was named after George Everest, a British surveyor in the 19th century.

"Mount Everest holds a special place in human consciousness," Dai remarked. "Physically, it represents the highest point on Earth, giving it immense significance due to its stature. Culturally, it is sacred to the local Sherpa and Tibetan communities. Globally, it symbolizes the ultimate challenge, representing human endurance and our desire to surpass perceived limits."

Disclaimer: This image is taken from Reuters