“Everest” is 15-50 meters higher because the river erodes the base of the mountain peak.
A new study has found that Mount Everest is rising 15 to 50 meters above normal levels as rivers erode rock and soil at the base of the peak, pushing it higher.
Mount Everest is rising 15 to 50 metres above normal levels as rivers erode rock and soil at its base, pushing it higher. Land loss in the Arun River basin, 75 kilometres away, is causing the world’s tallest mountain to rise by up to 2 millimetres a year, a new study has found.
“It’s like throwing cargo off a ship. The ship gets lighter and floats a little higher. Similarly, when the Earth’s crust gets lighter, it floats a little higher,” said Adam Smith, a co-author of the study.
The pressure from the collision of the Indian and Eurasian plates 40-50 million years ago created the Himalayas, and plate movement is still the main reason why the two plates continue to rise.
The Arun River network is one factor in the mountain’s rise, UCL researchers say. As the Arun River flows through the Himalayas, it erodes material – in this case the riverbed – out of the Earth’s crust. The forces exerted on the mantle, the next layer beneath the crust, are reduced, causing the thinner crust to bend and rise.
The research, published in the journal Nature Geoscience, says this is called an isostatic rebound effect, adding that the upward thrust is causing Everest and other nearby peaks, including the world’s fourth and fifth highest peaks, Lhotse and Makalu, to move upward.
“Everest and nearby peaks are growing because isostatic rebound is causing them to rise faster than they are eroding,” said Dr Matthew Fox, co-author of the study. “We can see these peaks are rising at about 2mm per year using GPS, and now we have a better understanding of what’s driving them.”
Some geologists who were not involved in the study say the theory seems plausible, but there are still many uncertainties in the research.
Mount Everest is located on the border between China and Nepal, and the northern part is on the Chinese side. The Arun River flows down from Tibet into Nepal, then joins two other rivers to form the Kosi River, which flows into northern India and joins the Ganges River.
This river is a source of large amounts of sediment due to the steep slopes of the mountains it flows through and the force of the river, which allows the river to erode large amounts of rocks and soil during its flow.
But the UCL researchers say the river was likely to have been truly “strong” when it merged with another river or body of water in Tibet 89,000 years ago, a relatively recent event on geological timescales.
Dr. Xu Han, a Chinese scholar from the China University of Geosciences and lead author of the study, said the change in Everest’s height highlights the dynamic nature of the Earth’s surface. “The interaction between the erosion of the Arun River and the upward pressure of the Earth’s crust has given Everest a push and pushed it higher than it should have.”
The Arun River could have the potential to erode vast quantities of rock and other material after it erodes other rivers or water systems in Tibet, a UCL study says.
Professor Hugh Sinclair, from the University of Edinburgh’s School of Geology, who was not involved in the study, said the underlying processes the UCL team had identified made perfect sense. But he added that the exact amount and timing of river erosion – the way a river cuts into the riverbed and deepens the channel and the subsequent uplift of the surrounding hilltops – was highly uncertain.
Second, Professor Sinclair said the distance the mountain had risen from the point of severe erosion in the area was extremely difficult to predict. “Even considering these conditions, however, the possibility that Everest’s elevation gain is linked to rivers is an exciting new insight.”
Source: BBC
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