Why is Mount Everest still growing taller?

Mountains are an important geomorphic unit on Earth, occupying about 25% of the world's land area. Under the influence of plate tectonics, mountains of varying sizes have developed all over the world.

They not only constitute the "skeleton" of the world's topography, but also create beautiful natural wealth for mankind. With their majestic and diverse bodies, they show their unique charm to the world and fascinate countless people.

When it comes to mountains, we have to mention the world-renowned Himalayas. Located on the southern edge of the Qinghai-Tibet Plateau, with an average altitude of 6,000 meters, it is the highest mountain range in the world and a masterpiece of nature. The Himalayas start from Nanga Parbat (8,125 meters above sea level) in Kashmir in the west and end at Nanga Bawa (7,782 meters above sea level) at the bend of the Yarlung Zangbo River in the east.

The mountain range has a large number of world-class peaks, including 40 peaks above 7,000 meters and 10 peaks above 8,000 meters (there are only 14 peaks above 8,000 meters in the world). The main peak is Mount Everest. According to the latest altitude data released by my country in December 2020, it is 8,848.86 meters, making it the world's highest peak.

The formation of mountains is inseparable from the movement of plate tectonics. During the process of plate subduction and collision, the plates will undergo strong deformation, compression, bending, and folding to form a series of mountain ranges of varying sizes. About 65 million years ago, the Indian Plate and the Eurasian Plate collided on land, and then the Indian Plate continued to subduct northward under the Eurasian Plate. The continuous compression of the two plates caused the shallow materials of the earth to rise and expose the surface, and finally formed the current Himalayas about 15 million to 10 million years ago.

To this day, the Indian Plate is still moving northward at a speed of 5 centimeters per year, and the seismic activity here is still very strong, which is the main reason why the height of Mount Everest still changes. For example, a study suggested that after the 8.1-magnitude earthquake in Nepal in 2015, the height of Mount Everest dropped by 2 to 3 millimeters.

How high can Mount Everest grow? In fact, this is a key scientific issue regarding the uplift and growth mechanism of the plateau. This interesting and complex issue is also at the forefront of current earth science research. Geologists around the world have done a lot of work in these areas.

There are many factors that control the height of mountains, mainly tectonic forces, climate-controlled erosion, and crustal isostasis. Tectonic forces, as the internal dynamics of the earth, thicken the crust through the subduction-collision process between plates, causing mountains to begin to rise.

In contrast, climate-controlled surface erosion is more specific, constantly removing material from high altitudes to limit the height of mountains. Finally, crustal isostasis keeps mountains and the underlying lithosphere floating on the asthenosphere, and the bending of the lithosphere feeds back to the increase or decrease of mountain mass.

Geologists agree that the height of a mountain range is the result of the three main processes described above, but complications arise because the different processes can operate out of sync.

The latest research published in Nature magazine shows that the Himalayas are a very active orogenic belt. Compared with the higher river erosion rate around the plateau, the high convergence rate between plates dominates. Obviously, tectonic action has become the main factor in the height of the Himalayas.

However, once the mountains reach the maximum altitude that the strength of the Earth's crust can sustain, the Himalayas continue to widen at a fixed height; climate-controlled erosion controls not the height of the mountains but their width.

In short, tectonic action, climate action and crustal equilibrium action jointly control the height of mountains, but which one plays a major controlling role still requires further research by scientists. The question of the height of mountains still requires a lot of observation and theoretical research.

This article is a work supported by Science Popularization China Starry Sky Project

Author: Dong Hanwen

Reviewer: Wang Licheng (Researcher at the Institute of Tibetan Plateau Research, Chinese Academy of Sciences)

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.