The highest peak in the world, Mount Everest, is 15 to 50 meters higher because of a river, because there is erosion of rocks and salt in its bed, which reach the top with the flow of water, according to a new study.
Soil washing in the Arun River 75 kilometers away from Mount Everest is contributing to its growth of no more than two millimeters a year, say researchers from University College London.
"It's a bit like unloading cargo from a ship. The ship becomes lighter and therefore floats at a higher point.
"Similarly, when the soil becomes lighter, it can float at a slightly higher point," Adam Smith, one of the authors of the study, told the BBC.
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The Himalayas were formed 40 to 50 million years ago due to the pressure caused by the collision of the Indian and Eurasian tectonic plates, and the movement of the plates is still the main reason for the continuous growth of this mountain in Asia.
But the Arun river basin also contributes, say researchers from London.
As it flows through the Himalayas, the river carries material that is in its bed and originates from the Earth's crust.
This reduces the pressure on the soil layer below the crust, causing the thin crust to bend and float upstream.
This phenomenon is called isostatic jump, and because of it, Mount Everest and other mountains in the area, such as the peaks of Loca and Makalu, the fourth and fifth highest peaks in the world, are growing, according to research published in the journal Nature Geosciences.
"Mount Everest and nearby peaks are growing because the isostatic jump is raising them faster than erosion is causing them to shrink," Matthew Fox, one of the researchers, told the BBC.
"Using GPS, we can see that they grow by about two millimeters every year, and now we better understand why this happens," he adds.
Some geologists who did not participate in the research say that the theory of scientists from London is plausible, but many aspects of it are still not clear enough.
Mount Everest is on the border of China and Nepal, but the northern part of the mountain is in China.
The Arun River flows through Tibet to Nepal, joining two other rivers to form the Kosi River, which flows through northern India and then flows into the Ganges.
Erosion is characteristic of the Arun due to the steep mountains it cuts into and the power it has, which enables it to carry away large amounts of rock and salt along its course.
But scientists from London point out that it most likely got its strength when it "took over" another river or some body of water in Tibet 89.000 years ago, which in terms of geology was in relatively recent history.
Su Han, an academic from the Chinese University of Geological Sciences, led the research during his time at University College London.
"The change in height of Mount Everest really shows us how dynamic the nature of the Earth's surface is.
"The relationship between the erosion of the Arun River and the pressure exerted by the Earth's mantle from above causes Mount Everest to be higher than it would be without it," says the expert.
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By taking over another water system in Tibet 89 millennia ago, the Arun probably also gained the capacity to wash huge amounts of rocks and other materials.
That's why what the researchers observed seems completely achievable, says Hugh Sinclair, an expert at the School of Geological Sciences at the University of Edinburgh, who was not involved in the study.
But there are still great uncertainties about the exact scale of the cutting and deepening of the river bed and the consequent uplift of the ground on the nearby mountain tops, according to Sinclair.
"First of all, it is challenging to predict the cutting of the beds of such large watersheds, which occurs when one river takes over another river or lake," he says.
The authors of the research also talk about this uncertainty.
Sinclair points out that it is very difficult to estimate to what extent the mountains could rise due to the intense erosion of the local river basin.
"In any case, despite these doubts, the possibility that part of the extraordinary uplift of Everest is related to the work of the river is an exciting concept," concludes the scientist.
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