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Location

The Canary Islands are more or less enclosed in a rectangular area from 13°30'W to 18°00'W and 27°30'N to 29°30'N. As a group, they stretch west to east over 450km (280 miles). Although administered by Spain, the mother country is 1100km (685 miles) away. The narrowest strait between the Canary Islands and Africa is a mere 110km (70 miles). The total land area is almost 7500km (2900 square miles), but the sea they occupy is 10 times that size.

Geology

La Geria on Lanzarote, where ash pits and semi-circular walls protect vines from the wind

Most of the world’s volcanic landscapes are formed where huge continental or oceanic ‘plates’ collide with each other. When continental plates collide, the Earth’s crust crumples upwards to form mountains, and when plates are torn apart, basaltic rock from deep within the Earth’s mantle erupts to form mountains. The Canary Islands, however, are different, and have a complicated geological history.

The African landmass is the visible part of a continental plate that extends into the Atlantic Ocean, but the Canary Islands lie within the oceanic crust of the eastern Atlantic Ocean, close to the passive junction with the African continental plate. It is thought that the islands now lie directly above a hot-spot, or mantle plume, some 2500km (1550 miles) deep within the Earth. The mantle plume is fixed, but the oceanic and African plates are drifting very slowly eastwards. Every so often a split in the oceanic crust opens above the mantle plume, allowing molten rock to vent onto the ocean floor. As more and more material erupts, it piles higher and higher until it rises from the sea. Each of the Canary Islands was formed this way.