The Jurassic age limestone is about 150 million years old and was laid down in a marine corridor that extended from the Gulf of Cádiz to Alicante between the present Atlantic Ocean and Mediterranean Sea. These seabeds were uplifted to an elevation of over 1300 meters during the Tertiary era, resulting in a modest mountain range of flat-lying limestone, which is rare in Andalucia. Later, a series of fractures, cracks and faults at right angles (generally NW-SE and NE-SW) were exploited by erosion and produced the alleys between large blocks of limestone visible today. The blocks themselves have been subjected to both dissolution by water (karstification) and freeze-thaw splitting action which, working on the limestone's horizontal beds, resulted in the various shapes visible today, many of which resemble, and have been named after, everyday objects such as the Sphinx, the Jug, the Camel, the Screw, etc. Other flat surfaces have been karstified into rugged, rocky lands where travel on foot is difficult.