Is it tectonic or erosion that controls the height of the mountains?

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If it is clear that mountains were born under the influence of compressive tectonic forces, their mature relief lives are governed by a balance between them. plate convergence rateisostatic equilibrium and abrasive processes.

Like every square centimeter of the Earth’s surface, mountains are indeed subject to erosion by wind and water and constant weathering. All the more because relaxation is important. These surface processes also play an important role in climate regulation, and certain weathering reactions are associated with CO fixation.2 atmospheric. Weathering of rocks also provides large amounts of nutrients that will enrich the oceans and support marine productivity. It is widely accepted that the uplift of the great mountain ranges is accompanied by an increase in rock weathering processes that can have a significant impact on the climate system. Climate and tectonics are therefore closely linked..

How can mountains maintain their height despite erosion?

However, it is not yet clear how these different forces that control the height of the mountains are balanced (or not) balanced in the very long run. It seems that, despite very high erosion rates, some active orogens still manage to “survive” and preserve their topography for hundreds of millions of years.

That’s why a research team set out to design a new numerical model that combines surface processes, tectonic forces, and lithospheric resistance. For this, they used a new parameter called the “Beaumont number” (Bm), referring to researcher Christopher Beaumont (Dalhousie University, Halifax, Canada). This dimensionless number makes it easy to quantify the different factors that control the topographical evolution of the reliefs and then identify the dominant one.

three kinds of mountains

Thus, three types of active orogen were identified. Type 1 (Bm>0.5) corresponds to an unstable state mainly controlled by tectonic forces and lithosphere dynamics. Therefore, mountains continue to grow despite the influence of surface treatments. This situation is for example of the two most important mountain ranges : The Himalayas and the Andes. Type 2 (Bm is approximately equal to 0.4-0.5) corresponds to a steady state dominated by tectonic forces. The height of the reliefs remains constant here, strong topographical growth tectonic plates and effective stabilization of lithosphere dynamics by surface processes. This is Taiwan’s situation. Type 3 (Bm<0.4) corresponds to a steady state, this time dominated by erosion. Elevation is also constant over time, but here it is erosion offset by tectonic. An example: the Southern Alps in New Zealand (despite the name, be careful, the Alps that define Western Europe's topography are by no means).

Climate, Crust Strength and Plate Convergence Rate

The new numerical model developed by the team thus makes it possible to measure the influence of various factors affecting the height of mountains. The main parameters that come into play here are the climate of the region, which directly determines the rate of erosion and weathering, but also the climate of the region. resistance of the lithosphereThis will govern the rebound capacity of the shell in response to wear, as well as the rate of convergence of the plates.

In a simplified way, the results published in the journal Nature To understand the topographic dynamics of a mountain range, it is sufficient to know whether the climate is wet or dry, whether the crust is strong or weak, and whether the plates are converging rapidly or slowly.

Is the height of mountain ranges affected by erosion or plate tectonics?

The origin of the uplift of mountain ranges has long been a subject of debate among scientists. Is this affected by elemental erosion, or could plate tectonics play a role? A new study offers an answer.

Article by Emma Hollen, published June 11, 2020

This is a debate that has long fueled the scientific community: does erosion determine the height of the summits of mountain ranges, or is their height affected by tectonic processes? A new study published in the journal Nature provides new answers that suggest that plate subduction At the origin of the rise of these rock giants would come to balance the corrosive action of the elements.

At the origin of the mountain ranges

highest mountain ranges Soil stand on the border between tectonic plates convergent. For example, the Himalayan range is the result of the collision between the Indian and Eurasian plates. Andes Cordillera South America, Nazca and Antarctica. this compression Pressures exerted by the last two against the South American plate over the last 20 million years have allowed the region’s elevation to exceed 1500 meters in places.

In this process called loss “The two plates move towards each other, until the oceanic plate sinks deeper into the ocean until it is forced to slide under the continental plate to continue its journey. terrestrial mantle. This geological embrace, strong seismic activity and volcanic; Over millions of years, it causes gradual and massive deformation of the upper plate, which in turn creates a mountain range or a mountain range. stone like the Aegean Sea.

A balance between erosion and subduction

Researcher Armin Dielforder and his team explain in their new study: erosion by the rivers and glaciers mountain peaks are not enough to drastically reduce the height of mountain ranges. by analyzing the features tectonic plates By calculating the forces that form the massifs and applied at the junction between them, the researchers were able to show a correlation between the forces at the edge of the plates on one side and the height and weight of the mountains on the other.

This correlation was observed for all massifs studied at various locations. latitudes and therefore different climates and erosion rate. As a result, erosion dulls the mountain peaks, while the force of subduction contributes to their continued uplift, giving the massifs the proportions we know today. This important discovery opens up new avenues in the study of the development and growth of mountains over the long term.

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