The Mediterranean region is an area of incomplete continental collision. It lies between the European and African plates, which have been converging since late Cretaceous time (80 Ma). Because the continental edges of Europe and Africa are irregular in shape, the Mediterranean region contains zones where the two continents have already collided and adjacent zones where the two continental masses have not yet collided. Within the convergence zone between Europe and Africa are small fragments made up of both oceanic and continental crust that move independently, or partly independently, from the large plates. The movements of these small fragments are responsible for the formation of all of the Alpine mountain belts west of central Turkey. In many cases the velocities of these small fragments may be much faster than those of Europe or Africa and their directions of motion can be oblique or even orthogonal to the direction of convergence between the two large plates. Old ocean floor has been subducted beneath the fragments and new ocean floor has been created in their wake by back-arc type extension.

Because the Mediterranean region is young and many of the tectonic systems within it are active today, it is possible to relate different structural and morphological styles present within Mediterranean mountain belts to the dynamic processes and larger-scale tectonic systems within the mountain belts formed. We recognize two fundamentally different structural styles in mountain belts of the Mediterranean region, and these mountain belts can also be shown to have formed in two different dynamic environments. Classic mountain belts with high topography, such as the Alps, also have cores of high-grade metamorphic rocks, display significant deformation of crystalline basement, and commonly develop antithetic thrust belts. These mountain belts have formed in areas where the two fragments were pushed together to form a mountain belt faster than the invervening crust was subducted. In contrast, other mountain belts have been formed in areas where the intervening crust was subducted faster than the two fragments were pushed together. These mountain belts look very different. They have low topography, low-grade metamorphism, lack significant deformation of continental crystalline basement, and display extensional deformation in the back-arc region. Examples of this type of mountain belt are especially well developed in eastern and central Europe, such as the Apennine and Carpathian mountain belts.

The concepts derived from studying these two different types of mountain belts within the Mediterranean region can be applied throughout the world and throughout geologic history. The geologic record contains some beautifully preserved examples of incomplete continental collision. In many cases, however, incompletely-collided zones are only the early stage in a progressive collision process, and mountain belts formed during the early stages of collision are strongly modified during subsequent post-collisional convergence. These mountain belts formed during the early stages of collision are difficult to recognize in areas where collision has continued to completion, but probably account for some of the paradoxical relationships observed in old collisional mountain belts.

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