Gibraltar, a 6km2 peninsula jutting south from Spain at the western entrance to the Mediterranean Sea, is dominated by its 424 m-high Rock: famous as a landmark to seafarers since ancient times. Twenty-five years ago, an article in Geology Today (1991, v.7, pp.95-101) interpreted the Rock as a partly overturned mass of Early Jurassic dolomitic limestone, thrust into position during continent-continent collision about 15-20 million years before present and shaped finally by shoreline processes active during Quaternary tectonic uplift. Later articles featured the complex of tunnels and chambers excavated between 1782 and 1968 by British military engineers within its 2.6 km-long main ridge (1992, v.8, pp.92-98), and the Neanderthals known to have used some of its caves (1997, v.13, pp.179-184). Significant aspects of the Rock's geological history have clarified since then.
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