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June 12 (UPI) -- What controls the upper limits of a mountain or mountain range's height? According to a new study, it's not weathering and erosion, as many geoscientists assumed. New analysis of convergent plate boundaries -- home to the planet's largest mountain ranges, the Andes and Himalayas -- suggests an equilibrium of crustal forces controls the height of mountains.
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Mountain ranges are formed along subduction boundaries, where one tectonic plate slides under another. Over millions of years, earthquakes crumple the crust, while tectonic forces continue to push crustal layers higher and higher.
For the study, a team of researchers at the GFZ German Research Center for Geoscience and the University of Münster used a diversity of data from the scientific literature, including seismic observations, subsurface heat-flow measurements and frictional energy estimates, to characterize the strength of plate boundaries and nature of forces acting on plate interfaces.
By comparing the subsurface frictional forces found beneath different mountain chains, including the Himalayas, Andes, Sumatra and Japan, scientists pinpointed the sources of stress that dictate mountain heights.
Their analysis -- detailed this week in the journal Nature -- showed the forces acting on the plate boundary remain in balance with the forces created by the weight and height of the rising mountains.
Though Earth's tallest peaks are found in a variety of climate zones, where weathering and erosion rates differ dramatically, the same equilibrium of forces was present throughout the world's mountain ranges.
"We show that the height of mountain ranges around the globe matches this elevation, irrespective of climatic conditions and the rate of erosion," researchers wrote. "This finding indicates that mountain ranges are close to force equilibrium and that their height is primarily controlled by the megathrust shear force."
