Corsica and killings culminated in the assassination of Prefect Claude Érignac in 1998. In 2013, Corsica hosted the first three stages of the 100th Tour de France, which passed through the island for the first time in the event's 110-year history. Corsica was formed about 250 million years ago with the uplift of a granite backbone on the western side. About 50 million years ago sedimentary rock was pressed against this granite, forming the schists of the eastern side. It is the most mountainous island in the Mediterranean, a "mountain in the sea". It is also the fourth largest island in
Invasion of Corsica (1794) in August 1794. Corsica proved a mixed asset for the British; the island's anchorages provided some relief for a fleet operating at the end of a long supply chain, but the instability of Corsican politics and repeated French efforts to disrupt British control consumed valuable resources. By late 1796, with the French victorious in Northern Italy and the Spanish declaration of war on Britain following the Treaty of San Ildefonso, British control of Corsica was no longer tenable. British forces withdrew from the island, which was rapidly seized once more by the French. Corsica is a large, mountainous island in