The Himalayan mountain range was formed around 50 million years ago in a collision between the Indian and Eurasian continental plates. They continue to be pressed together even today and are the main reason why the mountain mass is moving upwards.
But Mount Everest is growing more than previously thought. The estimated increase of one millimeter per year has been shown to be closer to two millimeters in new measurements.
Researchers at University College London are now pointing to the Arun River as a contributing cause of the growth. 89,000 years ago, it swallowed a smaller river, leading to an increased amount of water in the river and thus increased erosion.
Over the centuries, millions of tons of sediment have been washed away. When sediment is washed away from the riverbed, the soil layer becomes thinner, the pressure decreases, and you get a land uplift.
It's a bit like when you unload cargo from a ship. The ship becomes lighter and floats a little higher. Similarly, if the earth's crust becomes lighter – it can float a little higher, says Adam Smith, one of the researchers behind the study, to BBC.
