Plate Tectonics and Mountain Building

Abstract

One of the greatest strengths of the modern plate tectonics theory is its ability to explain the origin of virtually all of the present and most ancient mountain belts on Earth. In other words, mountain building (orogeny) stands in strong causal interrelation with the global plate drift pattern. The motor of orogeny is subduction. To enable subduction, a basin floored by oceanic crust must be present. The process of orogeny becomes initiated by subduction of ocean floor and finds its climax in the collision of continents and island arcs. Mountain belts are elongate zones characterized by crust thickened to more than 70 km, in comparison to normal continental crust that is 30–40 km thick. The most classical style of orogeny involves continental collision that follows a lengthy period of subduction and completes a Wilson cycle. Ensuing orogeny leads to crustal thickening, deformation, metamorphism, and uplift. This style is called the Alpine style of orogeny. In contrast, orogenic belts that face Pacific-style oceans do not culminate with continent–continent collision, but rather involve long periods of ocean-slab subduction beneath continental margins with repeated episodes of collision that involve island arcs, oceanic plateaus, and microcontinents. This orogenic style is exceptionally rich in volcanic/plutonic production and is called the Cordilleran style of orogeny.