Which factors control the height of mountains?

A study in Nature with a surprising finding: It is not erosion.


The highest mountain ranges on Earth -, for example, the Himalayas or the Andes – arise along convergent plate boundaries. At such plate boundaries, two tectonic plates push toward one another, and one of the dishes is constrained underneath the other into the Earth’s mantle.

During this process of subduction, string earthquakes tremor more than once happen on the plate interface, and more than a large number of years, mountain ranges are built at the edges of the continents.

Regardless of whether the height of mountain ranges is, for the most part, determined by tectonic procedures in the Earth‘s interior or by erosional processes sculpting the Earth’s surface has long been debated in geosciences.

Now, a group of scientists from Münster and Potsdam has found that the equilibrium of forces in the Earth’s crust controls the height of mountains.

Scientists have shown that erosion by rivers and glaciers has no significant influence on the height of mountain ranges.

A new study led by Armin Dielforder of GFZ German Research Centre for Geoscience has solved the longstanding debate by analyzing the strength of various plate boundaries and calculating the forces acting along with the plate interfaces.

Scientists calculated forces along different plate boundaries on the Earth. They utilized data that offers insight into the strength of plate boundaries. These data are derived, for instance, from heat flow measurements in the subsurface. The frictional energy thus impacts the heat flow at convergent plate boundaries at the interfaces of the continental plates.

One can imagine the formation of mountains using a tablecloth. If you place both hands under the cloth on the tabletop and push it, the cloth folds, and at the same time, it slides a little over the back of your hands.

The emerging folds would correspond, for instance, to the Andes, then sliding over the back of the hands to the friction in the underground. Depending on the characteristics of the rock, tensions also build up in the deep underground, which is discharged in severe earthquakes, especially in subduction zones.

Scientists gathered global data from the literature on friction in the subsurface of mountain ranges of different heights (Himalayas, Andes, Sumatra, Japan) and calculated the resulting stress and thus the forces that lead to the uplift of the respective mountains. Doing so, they showed that n active mountains, the force on the plate boundary and the effects resulting from the weight and height of the hills are in balance.

Such a balance of forces exists in all the mountain ranges studied, although they are situated in different climatic zones with broadly varying erosion rates. This outcome shows that mountain ranges can react to processes on the Earth’s surface and to develop with quick erosion so that the balance of forces and the height of the mountain range are maintained. This essentially new finding opens up various chances to examine the long-term development and growth of mountains in more prominent detail.

Journal Reference:
  1. Megathrust shear force controls mountain height at convergent plate margins. DOI: 10.1038/s41586-020-2340-7
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