Recent research indicates that Mount Everest, the tallest mountain on Earth, might owe part of its elevation to a river that erodes rock and soil at its base. According to a new study by researchers from University College London (UCL), the Arun River, located 75 kilometers (47 miles) away, is responsible for eroding material from the Earth’s crust, thereby indirectly facilitating the mountain’s ascent. This process could explain why Everest is currently 15 to 50 meters taller than it would have been otherwise, with the peak gaining up to 2 millimeters in height annually.

“It’s akin to throwing a load of cargo off a ship,” stated study co-author Adam Smith. “The ship becomes lighter and floats a little higher. Similarly, when the Earth’s crust becomes lighter due to erosion, it can float upward.”

The Himalayas, including Mount Everest, originally rose from the collision of the Indian and Eurasian tectonic plates, a geological event that occurred 40 to 50 million years ago. While tectonic movements remain a key factor in the mountains’ ascent, the latest research highlights the significant role that erosion from the Arun River plays through a phenomenon known as isostatic rebound.

How Erosion Contributes to Mountain Uplift

The Arun River flows through the Himalayas, eroding substantial amounts of rock and soil along its path. This reduction in landmass lightens the Earth’s crust in the region, decreasing the pressure on the underlying mantle (the layer beneath the crust). As the crust becomes less dense, it can float higher, leading to the upward movement of the surrounding peaks, including Everest. This upward shift is driven by isostatic rebound.

The UCL team’s findings, published in Nature Geoscience, reveal that this erosion-driven uplift is enabling Everest and neighboring peaks, such as Lhotse and Makalu, to grow more rapidly than they are being eroded. Co-author Dr. Matthew Fox noted that GPS instruments measure this growth at approximately two millimeters per year, providing new insights into the mechanisms behind this rise.

The Impact of the Arun River

The Arun River originates in Tibet, flowing into Nepal before merging with two other rivers to form the Kosi, which ultimately meets the Ganges in northern India. The steep terrain and powerful currents of the Arun River allow it to erode significant amounts of material as it traverses the Himalayas.

Interestingly, the study suggests that the Arun River’s erosion capabilities increased dramatically around 89,000 years ago when it likely “captured” another water source in Tibet. This event, which is relatively recent in geological timescales, may have provided the river with the ability to erode larger quantities of rock and soil, contributing to the current uplift of Everest.

Dr. Xu Han, the lead author of the study from China University of Geosciences, emphasized that the interplay between the river’s erosion and the upward pressure from the mantle is boosting Mount Everest’s height. “The changing height of Mount Everest underscores the dynamic nature of the Earth’s surface,” he remarked.

Expert Opinions and Research Uncertainties

While some geologists not involved in the study find the theory plausible, they also acknowledge uncertainties in the findings. Professor Hugh Sinclair from the University of Edinburgh, who was not part of the research, pointed out that predicting how rivers like the Arun incise into their beds and influence surrounding elevations is complex. The precise amounts of erosion and the resulting uplift are challenging to quantify accurately.

Sinclair noted that it is particularly difficult to estimate how far the effects of localized erosion can extend in terms of mountain uplift. Despite these uncertainties, he believes the idea that some of Everest’s remarkable height is linked to river erosion provides “an exciting insight.”

The study’s authors recognize these limitations but maintain that isostatic rebound, driven by erosion, plays a significant role in the height of Everest and nearby summits.

The Dynamic Landscape of Everest

Mount Everest is situated on the border between China and Nepal, with its northern face in China. The Arun River flows from Tibet through Nepal before joining the Kosi and eventually the Ganges in India. Known for carrying a substantial amount of silt due to the steepness of the terrain, the river’s power to erode rock and soil has likely increased following the capture of another river system in Tibet thousands of years ago.

This research highlights the complexity of the Earth’s surface and the myriad factors influencing changes in the landscape, including river erosion. As the tallest mountain in the world, Everest has long intrigued scientists and adventurers alike, and this new study adds another fascinating layer to the narrative of its ongoing ascent.

While tectonic forces continue to be the primary driver of the Himalayas’ elevation, the erosion from rivers like the Arun may be providing Everest and its neighboring peaks with an additional boost. The interplay between river erosion and the Earth’s crust demonstrates how dynamic and interconnected natural processes can be, offering a deeper understanding of the geological forces shaping our planet.