The lava lake of Erta Ale Volcano (Ethiopia)

Erta Ale is 613 metres (2,011 ft) high, with one or sometimes two active lava lakes at the summit which occasionally overflow on the south side of the volcano. It is notable for being the longest-existing lava lake, present since the early years of the twentieth century (1906). Volcanoes with lava lakes are very rare: there are only five in the world.

Erta Ale means smoking mountain in the local Afar language and its southernmost pit is known locally as the gateway to hell. In 2009 it was mapped by a team from the BBC using three dimensional laser techniques. As the lakes have searingly hot temperatures, laser scanning, which can map any surface at a distance, was used.