Increasing height of Mount Everest

   Everest's Height

  Scientists say a river "takeover" in the Himalayas 89,000 years ago may have been behind Everest's height
 Mount Everest or Sagarmatha (top), the world's highest peak at 8,848 meters (29,028 feet), is seen alongside the 6,812-meter (22,349-foot) higher Mount Ama Dablam (bottom r) in this aerial view from April 22, 2007. 
  A river "takeover" event in the Himalayas 89,000 years ago resulted in enough erosion that ultimately pushed Mount Everest's peak up 164 feet, a new study suggests.

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  A river about 46 miles (75 kilometers) from Everest was "taken over" by another about 89,000 years ago, according to a new study, Live Science reports.

The erosion caused by this event carved out a huge gorge. This led to a loss of land area that made the mountain experience a major growth spurt.

Notably, Mount Everest is the highest peak on Earth at 29,031.69 feet (8,848.86 m).
 However, study co-author Adam Smith, also a researcher in Earth Sciences at University College London, told Live Science that the mountain is "higher than it should be."
The height difference between most mountain peaks in the Himalayas is about 164 to 328 feet (50m -100m), but Everest is 820 feet (250m), higher than the next highest mountain, K2. "That probably indicates something interesting is going on," Smith said.

 Additionally, GPS data shows that Everest is rising at a rate of about 0.08 inches (2 millimeters) per year. This is faster than the expected rate of rise for the mountain range.
To find out the real reason, scientists looked to see if there were unusual Himalayan rivers behind it.

"The Arun River is strange, because it flows in an L-shape," Smith said. "Most rivers resemble trees, with a relatively straight trunk, and branches (supports) flowing into the trunk. However, the Arun flows east to west along its upper reaches, before making a 90-degree turn and flowing south through the Himalayas. This suggests that the river may have recently changed its shape, and perhaps 'captured' another river."
 The results then suggested that the Arun River, now a major tributary of the Kosi River, was captured by the Kosi about 89,000 years ago.
As a result, this diverted river led to increased river erosion, creating the Arun River Gorge.

The researchers argue that the creation of the gorge and river erosion must have removed enough land mass to lighten the surrounding terrain, causing Everest to emerge. According to models, since the capture event, the mountain has risen between 50 and 164 feet.