Mount Everest grows: How erosion and mantle dynamics lift the peak

The highest peak on Earth is a source of many dreams and aspirations but also broken hearts and lost lives. It is estimated that currently, there are over 300 bodies on the mountain slopes of daredevils who perished on their way to the summit or while returning to the camp. Mount Everest has also claimed the lives of seven Poles who died due to avalanches and falls. Despite this, there is no shortage of adventurers who risk everything to reach the summit. Among them was influencer Patec, who, on 31 May 2024, stood at the highest point on Earth.

It turns out that climbers who reached Mount Everest in 1953, during the first ascent, were lower than those climbing the mountain in 2024. Why? Researchers from University College London argue that Mount Everest grows by as much as 2 millimetres annually. This is due to the action of the Arun River, which causes landmass loss in its basin located 75 kilometres from the base of the highest mountain in the world. In an interview with "BBC," Adam Smith, a study co-author, explained:

"It’s a bit like throwing a load of cargo off a ship. The ship becomes lighter and so floats a little higher. Similarly, when the crust becomes lighter… it can float a little higher."

Researchers explain that as the Arun River flows through the Himalayas, it removes material, more precisely the riverbed, from the Earth's crust. Consequently, the pressure on the Earth's mantle, the layer below the crust, decreases, causing the thin crust to bend and lift upward, thus raising the peaks located on it. This effect is called "isostatic rebound." The study published in "Nature Geoscience" indicates that thanks to this force, Mount Everest has not only risen but also the fourth and fifth highest peaks on Earth, Lhotse and Makalu.

In an interview with BBC, Dr Matthew Fox said, "We can see them growing by about two millimetres a year using GPS instruments, and now we have a better understanding of what’s driving it."

Dr Xu Han from the China University of Geosciences, the study's lead author, adds: - The changing height of Mount Everest highlights the dynamic nature of the Earth's surface. The interaction between the erosion of the Arun River and the pressure from the Earth's mantle gives Mount Everest an additional boost, raising it higher than it otherwise would be.

Professor Hugh Sinclair from the School of Geosciences at the University of Edinburgh doubts his colleagues' study. The scientist admitted that the conclusions from the analysis are promising, but it is difficult to definitively assess the impact of river erosion on the rising Earth's surface. The researcher explained:

"Firstly, predicting river incision of such large catchments in response to drainage capture (one river capturing another river or lake) is challenging."

Sinclair added that the distance to which mountains rise from the point of intense, local erosion is extremely difficult to predict. However, even considering these reservations, the possibility that part of Everest's exceptional height is associated with the river presents an exciting prospect.

The scientists responsible for the study admitted that Professor Sinclair's doubts are valid.