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Geology

Corsica is often referred to as ‘the Granite Isle’, and it is easy to dismiss the whole island simply as one enormous granite massif, but this would be wrong. Corsica is geologically divided into two parts by a line running very roughly from Île Rousse on the north coast, through Corte in the middle of the island, to Favone on the east coast.

Everything west of this line is referred to as ‘Hercynian Corsica’, named after a mountain-building era that occurred between 345 and 225 million years ago. The bedrock in this, the greater part of Corsica, is essentially a massive granite intrusion. It was pushed into the Earth’s crust under immense pressure and temperature, so that the rock was in a molten state. As it cooled over a long period of time, coarse crystals formed, chiefly of quartz, feldspar and mica. Geologists sub-divide the granite according to its mineral composition, which varies from place to place, especially around the northwest of the island. Granophyres and quartz porphyries are common, and conspicuous linear dykes have been intruded into some rocks. The mountains that were raised during the Hercynian era are long gone, and the granite mountains of Corsica are merely their deepest roots.