Tibet: Mount Everest, the tallest mountain on Earth, continues to surprise scientists with its ongoing growth. Recent research by BBC has revealed that this iconic peak is not only increasing in height but is doing so at a rate of about 2 millimetres per year—double the figure predicted by historical rock data. This accelerated growth is attributed to geological changes triggered by rivers merging nearly 90,000 years ago. Photo courtesy of BBC News.

A study published in Nature Geoscience suggests that when two rivers converged in the Himalayas, they initiated a series of geological processes that contributed to an increase in Everest's elevation by as much as 50 meters. Researchers analysed health records from the regions surrounding Everest, focusing on the effects of the Arun River, which has carved a deep gorge through the heart of the Himalayas.

Jingen Dai, a researcher at the China University of Geoscientists and co-author of the study, emphasized the intricate relationship between geological processes and river dynamics. “This research highlights the complex interplay between different Earth processes,” Dai noted. “It shows how changes in rivers can affect even the world's highest mountain.”

Over the past 30 million years, Everest has risen more than 8 kilometres, primarily due to the collision of the Indian and Eurasian tectonic plates. This tectonic activity has pushed the mountain upward, but the reasons behind its current growth rate had remained unclear—until now.

The study revealed that the Arun River, which drains a large area north of Everest, underwent significant changes after merging with another river approximately 89,000 years ago. This event, termed “drainage piracy,” amplified the river’s erosive power, leading to the deep gorge now characteristic of the region. As the Arun carved away vast amounts of rock, the surrounding area—including Mount Everest—began to rise in response, a phenomenon known as isostatic rebound.

Sara Polanco, a geologist at the University of Sydney, explained the mechanics of this process: “As the river eroded the rock, the Earth compensated for the material removed, leading to uplift.” This natural reaction is akin to a boat rising in water when weight is taken off, allowing for continued elevation of the mountain.

The study's findings indicate that isostatic rebound alone could account for an additional 0.16 to 0.53 millimetres of Everest’s annual growth. However, researchers are not stopping there; they are now investigating sediments in the surrounding basin to glean further insights into this ancient river system and its long-term effects on the landscape.

Understanding the intricate history of the Arun River and its role in shaping Everest's height is likened to reading a geological diary of the region. Dai expressed anticipation for future discoveries, stating, “It’s like reading the region's diary from thousands of years ago, and we can’t wait to see what other secrets it might reveal.”

While Mount Everest's growth is gradual, it underscores the dynamic nature of our planet's geology. Everest’s height was last officially updated in 2020, measuring 8,848.86 meters, but with ongoing studies, it is clear that this majestic peak has not yet finished its ascent.