Scientists have come up with a new classification scheme for mountain belts that uses just a single number to describe whether the elevation of the mountain belt is controlled mainly by weathering and erosion or by properties of the Earth’s crust, i.e., the lithospheric strength: the “Beaumont number” (Bm). It’s named after Chris Beaumont, a scientist who, together with his team, developed coupled models of surface processes and tectonic forces. The scientists report about their findings in the current issue of Nature.
A Beaumont number between 0.4 and 0.5 means that the mountains are in a so-called flux steady state in which the controlling factors of mountain growth are tectonic forces and the lithospheric strength, balanced by weathering processes as, for example, in Taiwan. With a Bm value lower than 0.4, mountains are also in a flux steady state but with erosion as controlling factor like the Southern Alps of New Zealand. A Beaumont number above 0.5 means that the mountains still grow (non-steady state) with lithospheric strength controlling the process. Examples for this type are the Himalaya-Tibet mountains and the Central Andes.
This classification is resolving a long-standing question whether tectonic forces and strength of the Earth’s crust are the controlling factors of mountain elevation or weathering processes. The new study says it can be one or the other – depending on geographic location, climate and underground properties.
Read more at GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre
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