In the Himalayas you will find the highest mountains in the world, such as Mount Everest or K2, with peaks of 8849 and 8611 meters high. The average height of the mountain range is five kilometres above sea level. Earth scientists Kai Xue, Vincent Strak and Wouter Schellart have found a possible explanation why this is the case.
The Himalayas were formed when two continents, India and Asia, collided. But that doesn't explain why the Himalayas are so high. Other collisional mountain ranges, such as the Alps or the Pyrenees, have average heights of about two kilometres. The top of these mountains is also lower: for example, the top of Mont Blanc is 4809 meters above sea level.
Continental subduction
The scientists therefore simulated the collision between India and Asia in a laboratory. They investigated how India made a dent in the Asian tectonic plate, and what driving forces cause India to move northward. This process not only causes crustal thickening and mountain formation, but also continental subduction, a process in which the Indian continental plate subducts beneath Asia.
Lying flat in a unique way
What the researchers did not expect is that the Indian plate is initially lying flat beneath the Asian plate, translated into terrestrial values of about 300-500 km. It turned out that this way of lying flat does not occur in any other collisional mountain range. This makes the Himalayas unique.
Experimental laboratory research
The laboratory experiments showed that this process causes the Asian plate to be pushed up an additional two to four kilometres, on top of the increase in height due to crustal thickening of the Asian plate. According to Kai Xue and her fellow researchers, this shows why experimental laboratory research is so important. “We could not have predicted the dynamics of flattening with theoretical research alone. Without experimental research, no connection would have been discovered between a subducted continental plate lying flat, and the highest mountain range on Earth.” The research was published in Scientific Reports.
Picture: Kai (left) and Vincent (right), as they prepare an experiment in the KEG Lab simulating the India-Asia collision (photo credit: W.P. Schellart).