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Calton Hill is a geological Site of Special Scientific Interest (SSSI) in Derbyshire,[1] about 3½ miles (5.6 km) east of Buxton.[2] It was the site of a volcanic vent about 330 million years ago, during the Carboniferous period.[1]
The site’s geological importance lies in the nodules of rock found in its basalt lava: spinel lherzolites and harzburgites formed deep within the Earth’s crust, and brought to the surface by volcanic activity. Such rocks are very rare, and Calton Hill is the only site in England where they have been found.[1]
The hill rises about 200 ft (61 m) above the general level of the limestone plateau on which it sits,[2] and from 1906 until 1969 was quarried for road material. The quarry is now filled in and landscaped over.[3]