The Gibraltar Limestone consists of grayish-white or pale-gray compact and sometime finely crystalline, medium to thick bedded lime stones and dolomites that locally contain chert seams.
This formation comprises about three quarters of the Rock of Gibraltar. Geologists have found various poorly preserved and badly eroded and rolled marine fossils within it. The fossils found in the Gibraltar Limestone include various brachiopods, corals, echinoid fragments, gastropods, pelecypods, and stromatolites.
Today, the Rock of Gibraltar forms a peninsula jutting out into the Strait of Gibraltar from the southern coast of Spain. The promontory is linked to the continent by means of a sandy tombolo with a maximum elevation of 3 m (9.8 ft).
To the north, the Rock rises vertically from sea level up to 411.5 m (1,350 ft) at Rock Gun Battery. The Rock’s highest point stands 426 m (1,398 ft) above the strait at O’Hara’s Battery. The Rock’s central peak, Signal Hill, stands at an elevation of 387 m (1,270 ft).
The near-cliffs along the eastern side of the Rock drop down to a series of wind-blown sand slopes that date to the glaciations when sea levels were lower than today, and a sandy plain extended east from the base of the Rock.
On the 2nd of January 1492, after five years of war, the Moorish emirate in Spain came to an end with the Catholic Monarchs’ capture of Granada. The Jews of Gibraltar were, like that elsewhere in the kingdom, expelled from Spain by order of the monarchs in March that year.
Gibraltar was used by Medina Sidonia as a base for the Spanish capture of Melilla in North Africa in 1497. Two years later the remaining Moors of Granada were ordered to convert to Christianity or be expelled. Although some did convert, most left for North Africa, many of them travelling by means of Gibraltar.
The seas around Gibraltar continued to be dangerous for decades to come as Barbary pirate raids continued; although a small squadron of Spanish galleys was based at the port to counter pirate raids, it proved to be of limited effectiveness and many inhabitants were abducted and sold into slavery by the pirates.
The problem worsened significantly after 1606, when Spain expelled its entire population of 600,000 Moriscos – Moors who had converted to Christianity. Many of the expellees were evacuated to North Africa via Gibraltar but ended up joining the pirate fleets, either as Christian slaves or reconverted Muslims, and raided as far afield as Cornwall.
Gibraltar would later become part of the Kingdom of Granada until 1309 when Castilian troops briefly occupied it. In 1333 the Muslim Spain invaders, Marinids, conquered Gibraltar, but ceded it to the Kingdom of Granada in 1374.
The Duke of Medina Sidonia re-conquered Gibraltar in 1462, finally ending 750 years of Moorish control. Gibraltar may have been the place where the Neanderthals died out. A study published in Nature in 2006 suggested they were living in a cave site on the south-east of Gibraltar up to 24,000 years ago (later than the 30,000 years previously thought).