E-Paper
Kosi river linked to rise of Mount Everest: Study
A study reveals that river erosion has caused Mount Everest to rise 15-50 meters over 89,000 years, continuing its ascent by 2 mm annually.
At 8,849 meters high, Mount Everest, also known as Chomolungma in Tibetan or Sagarmāthā in Nepali, is the tallest mountain on Earth, and rises about 250 meters above the next tallest peak in the Himalayas. Everest is considered anomalously high for the mountain range, as the next three tallest peaks – K2, Kangchenjunga, and Lhotse – all only differ by about 120 meters from each other. Ten of the 14 world’s highest peaks are found in Himalayas and most of them are witnessing an uplift like Everest.
The study by researchers at UCL said that the Mount Everest is about 15 to 50 meters (50 to 165 feet) taller than it would otherwise be because of uplift caused by a nearby eroding river gorge, and continues to grow because of it.
Mount Everest, the study said, was rising by 2 mm every year because of erosion from a river network about 75 kilometers from Mount Everest is carving away a substantial gorge and the loss of this landmass is causing the mountain to spring upwards by as much as 2 millimeters a year.
“A significant portion of this anomaly can be explained by an uplifting force caused by pressure from below Earth’s crust after a nearby river eroded away a sizeable amount of rocks and soils. It is called “isostatic rebound”, where a section of the Earth’s crust that loses mass flexes and “floats” upwards because the intense pressure of the liquid mantle below is greater than the downward force of gravity after the loss of mass.
“It’s a gradual process, usually only a few millimeters a year, but over geological timeframes can make a significant difference to the Earth’s surface,” the study said.
The river in question is Arun that starts from Tibet as Phung Chu and is one of the seven rivers that forms Kosi river network in Nepal before flowing into India from Bihar. Today, the Arun River runs to the east of Mount Everest and merges downstream with the larger Kosi River system. Over millennia, the Arun has carved out a substantial gorge along its banks, washing away billions of tonnes of earth and sediment, the study said.
Co-author Dr. Jin-Gen Dai of the China University of Geosciences, said: “An interesting river system exists in the Everest region. 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.”
