Nearby river contributes to the rise of Mount Everest, says new study

Nearby river contributes to the rise of Mount Everest, says new study

Sub :Geo

Sec: Oceanography

Context:

• Mount Everest, the world’s tallest mountain at 8,849 meters, is growing faster than expected.
• A recent study suggests that over the past 89,000 years, it has grown 15 to 50 meters higher than anticipated.
• The reason: A nearby river is playing a crucial role.

Details:

• The Arun River, located 75 km from Everest, is eroding rock and soil at the mountain’s base.
• This erosion is causing Everest to rise by up to 2 mm per year.
• The process contributing to this growth is called “isostatic rebound.”

What is Isostatic Rebound? 

• Isostasy (Greek isos “equal,” stasis “stand still”) is a term in geology to describe the state of mass balance (equilibrium) between the Earth’s crust and upper mantle.
• It describes a condition in which the mantle tends to balance the mass of the crust in the absence of external forces.
• Imagine the Earth’s crust as a floating object on a semi-liquid layer. When weight is removed from the surface (like eroded rock), the crust rises slightly, similar to a boat rising when cargo is unloaded.

The River’s Role:

• About 89,000 years ago, the Arun River merged with the Kosi River.
• This merger led to increased erosion, removing large amounts of rock and soil.
• The reduced weight in the region near Everest allowed the mountain to rise more quickly.
• Study Findings:
  • Isostatic rebound accounts for about 10% of Everest’s annual uplift rate.
  • Neighbouring peaks like Lhotse and Makalu are also affected.

However, some experts are skeptical:

• The timing of the river merger is uncertain.
• Dating river deposits and erosion rates is challenging.
• Some geologists believe river erosion may have little impact on mountain uplift.

Arun river:

• It is a transboundary river that is part of the Koshi or Sapta Koshi river system in Nepal.
• It originates in the Tibet Autonomous Region of the People’s Republic of China where it is called the Phung Chu or Bum-chu.
• Mouth: Confluence with Sun Koshi and Tamur River to form Sapta Koshi
• Tributaries:
  • Left- Yeru Tsanpo, Trakar-chu
  • Right- Barun River

Source: IE