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Examples of Collisional Tectonics

The Swiss Alps

Tectonic History

The Swiss Alps are a mountain range that formed after the break-up of the supercontinent Pangea. During the mesozoic, there was an ocean that separated Europe from Africa called the Tethys Ocean. The subduction of this basin and the collision of Africa with the Eurasian plate is what caused the formation of these mountains. There were two main episodes of orogenisis, one during the Cretaceous causing the formation of the eastern and western Alps, the second during the Tertiary resulting in the formation of the central Alps. These episodes of deformation and orogeny scaped off and thrusted large portions of sediments from both the Eurasian and African Plates that are now part of the Alps. These features are called nappes are only a few kilometres thick but still contribute to overall continental thickening. The final collision between Africa and Eurasia also uplifted portions of oceanic crust called ophiolites into the orogeny (Giovanni, 2003). The Alps are a highly complex regime comprising both ophiolites and nappes, as well as high grade metamorphism, faulting and folding.

The Alps are an example therefore of two collisional boundaries; ocean-continent followed by continent-continent.

Click here for greater detail on the tectonic history of the Alps

collision
Fig.6.1. This figure shows the subduction of the Tethys Ocean beneath the Eurasian Plate

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Fig.6.2. This figure illustrates the continental collision between Africa  and Eurasia


Geology of the region

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Fig.6.3. The current geology of the Alps

The diagram below is a close-up of the map above, focusing particularly on the Molasse Basin, formed from the deposition of eroded material from the Alps, particularly during the Tertiary orogeny. This basin is believed to be the result of  the down-going of the European plate under the thrust load coming from the south (Giovanni, 2003).
molasse
Fig.6.4. The major basins of the Alps
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