Scientists have discovered why some mountains are higher than others
A new study by German scientists shows that the height of the largest mountain ranges such as the Andes or the Himalayas, is not determined by the ratio of the speeds of rise and erosion, as previously thought, and tectonic forces holding the mountain at a certain level. The results were published in the journal Nature.
The highest mountain chains on Earth occur along the convergent boundaries of lithospheric plates. On such boundaries one of the plates is indented under another into the mantle of the Earth. This process is called subduction. Over millions of years of interaction in the collision point of the slabs of the mountains rise.
Scientists from the German research center for Geophysics, GFZ in Potsdam and münster University analyzed the strength of various lithospheric plates and calculated the forces acting along the boundaries of their section. These data were obtained from measurements of heat flux at the boundaries of converging plates, which in turn depends on the energy of friction between the lithospheric plates.
The model takes into account the shear force along the active subduction faults, and rheological properties of the plates. Shear forces create mountains for lateral support, which prevents their destruction under its own weight and reduces the effect of gravity. The authors did not take into account processes on a local scale, such as the growth of individual volcanoes because of the activity of the magma.
The simulation results showed that the height of the mountains depends on the balance of tectonic forces and isostatic equilibrium of the crust and mantle that keeps the mountains afloat over the hot and soft material of the mantle, like an iceberg floating in the water.
Scientists have calculated stress results, which, in their opinion, are responsible for lifting or lowering ranges. It turned out that all studied mountain building in different heights — the Andes, the Himalayas, the mountains of Japan and Sumatra — are force balance, although they are located in different climatic zones with very different rates of erosion.
Under the new model, with rapid erosion to reach equilibrium, the growth rate of mountain ranges increases, while their height remains unchanged. This is a fundamentally new and important discovery in the field of Earth Sciences.
For the mountains along the continental margins on subduction zones, the most important factor, as scientists have found, it becomes a tectonic power shift in the plane of the fault. It is the combination of horizontal and vertical stresses determines the height of mountain ranges.
The authors suggest that tension in the crust directly below the mountains is neutral — horizontal compression from tectonic forces podhodyashaya plate and vertical compression due to the weight of the column of rock is the same.
Since the weight of the pillar rocks is proportional to its height, seismic force, calculated for each boundary of the plate can thus be used to predict the maximum heights of the mountains.
The authors note that the findings of the study relate primarily to the ridges located above the subduction zones. To be extended to all mountains of the world, need more observations and theoretical constructions.