Mount Everest, also known as Chomolungma in Tibetan or Sagarmāthā in Nepali, is about 15 to 50 m taller than it would otherwise be because of uplift caused by a nearby eroding river gorge, and continues to grow because of it, according to new research.
Han et al. found that erosion from a river network about 75 km from Mount Everest is carving away a substantial gorge; the loss of this landmass is causing the mountain to spring upwards by as much as 2 mm a year and has already increased its height by between 15 and 50 m over the past 89,000 years. Image credit: Truthseeker08.
Formed by the subduction of the Indian tectonic plate under the Eurasian plate, the Himalayas host some of Earth’s highest mountains.
Mount Everest stands at 8,849 m above sea level — about 250 m higher than the Himalaya’s other tallest peaks.
Previous analysis of GPS data suggests recent uplift of Everest of about 2 mm per year, which exceeds the expected uplift rate of the mountain range, suggesting there may be a mechanism other than the ongoing regional tectonics contributing to this process.
“Mount Everest is a remarkable mountain of myth and legend and it’s still growing,” said University College London Ph.D. student Adam Smith.
“Our research shows that as the nearby river system cuts deeper, the loss of material is causing the mountain to spring further upwards.”
In the study, Smith and his colleagues investigated whether the changes to the mountain’s neighboring rivers could have contributed to the recent uplift of Everest.
They used numerical models to simulate the evolution of the Kosi River network to compare it to existing topography.
The models suggest that the Arun River — a main tributary of the Kosi River — was involved in the capture of another river 89,000 years ago.
The diversion of river water led to a pulse of increased river erosion as the river adjusted to its new path and resulted in the creation of the deep Arun River Gorge.
“Today, the Arun River runs to the east of Mount Everest and merges downstream with the larger Kosi River system,” Smith said.
“Over millennia, the Arun has carved out a substantial gorge along its banks, washing away billions of tons of soil and sediment.”
“An interesting river system exists in the Everest region,” said Dr. Jin-Gen Dai, a researcher at the China University of Geosciences.
“The upstream Arun River flows east at high altitude with a flat valley.”
“It then abruptly turns south as the Kosi River, dropping in elevation and becoming steeper.”
“This unique topography, indicative of an unsteady state, likely relates to Everest’s extreme height.”
The authors argue that although erosion would have lowered the elevation locally along the river channel, the relatively sudden removal of the eroded mass from the creation of the gorge would have triggered the surrounding landscape including Mount Everest to compensate with surface uplift.
Although the contribution may be small compared to tectonic processes, river capture can play a role in both the erosion and ascent of high topography.
“Mount Everest and its neighboring peaks are growing because the isostatic rebound is raising them up faster than erosion is wearing them down,” said Dr. Matthew Fox, a researcher at University College London.
“We can see them growing by about two millimeters a year using GPS instruments and now we have a better understanding of what’s driving it.”
“The changing height of Mount Everest really highlights the dynamic nature of the Earth’s surface,” said Dr. Xu Han, a researcher at the China University of Geosciences.
“The interaction between the erosion of the Arun River and the upward pressure of the Earth’s mantle gives Mount Everest a boost, pushing it up higher than it would otherwise be.”
The study was published in the journal Nature Geoscience.
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X. Han et al. Recent uplift of Chomolungma enhanced by river drainage piracy. Nat. Geosci, published online September 30, 2024; doi: 10.1038/s41561-024-01535-w
