Mount Everest is the highest mountain in the world, and it’s still growing. But that’s not because he’s gaining mass. Like researchers now in the specialist journal Nature Geoscience According to reports, the opposite is the case. The extraordinary height and current growth of the mountain could therefore have at least something to do with a nearby river. According to a computer model, about 89,000 years ago the Arun River carried so much water that it carved a deep valley in the Himalayas. The washed away rock reduced the weight of the mountain on the earth’s mantle and thus led to an elevation of the terrain in the mountain, which pushed Mount Everest 15 to 50 additional meters higher. The process continues to this day. As a team led by Jin-Gen Dai from the China University of Geosciences in Beijing reports, Mount Everest is getting higher by around two millimeters every year.
The Himalayas are folded mountains formed by the collision of the Indian continental plate with Eurasia. At 8,849 meters above sea level, Mount Everest towers over the next highest eight-thousander peaks by more than 200 meters. This is surprising considering that the tectonics in the Himalayas are relatively uniform, write the study authors. They wanted to find out whether processes in certain river systems contributed to this extraordinary height.
The so-called isostatic ground uplift is a process that has been well studied in northern areas such as Scandinavia, Canada and Siberia: after these areas were freed from an ice sheet up to three kilometers thick at the end of the last ice age around 11,700 years ago, this decreased Weight with which the earth’s crust pressed into the viscous part of the earth’s mantle. The result was a buoyancy and a ground elevation of several 100 meters. Something similar happens when water masses remove rock through erosion, which reduces the pressure on the Earth’s mantle.
The power of two combined rivers has carved a deep gorge
To study this effect around Mount Everest, Dai and colleagues developed a computer model. They used this to simulate the force that flowing water exerts on the bottom and sides of the riverbed. The current appearance of the River Arun was the starting point. “The Arun River drains the southern expanses of Tibet and the northern slopes of Mount Everest before flowing through a narrow gorge that has a height difference of seven kilometers over 35 kilometers.” The researchers suspected that such a landscape could only be formed by enormous masses of water could.
Using the model, the researchers went back in time and simulated river development under different circumstances. The simulations suggest that erosion created a connection between the Arun and another river around 89,000 years ago. As a result, water from the other river was diverted into the Arun, which suddenly had a lot more water. Geologists call this process river tapping. The combined hydropower probably created the deep gorge.
The ground uplift as a result of severe erosion primarily affected the river itself, but also, to a lesser extent, the surrounding area, which includes Mount Everest. Depending on how large the ground uplift was, Mount Everest could have been lifted 15 to 50 meters in height. According to the simulations, the effect still contributes 0.16 to 0.53 millimeters to the annual rise of Mount Everest. “Our study uncovers a previously unrecognized additional mechanism of rock uplift that has been active since river tapping,” write Dai and colleagues.