Erta Ale is a continuously active basaltic shield volcano in the Afar region of north-eastern Ethiopia, the most active volcano in Ethiopia. It is in the Afar Depression, a badlands desert area spanning the border with Eritrea, and the volcano itself is surrounded completely by an area below sea level, making it a relatively low-elevation volcano.
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”.
Dallol is famous for its hot brine, and multicolored white, pink, red, yellow, green, gray and black salt deposits, hot springs and miniature geysers. These bizarre structures form in a complex interaction of solution and crystallization processes driven by hydrothermal waters and rapid evaporation.
Dallol overlies several km of Quaternary evaporates which contain large amounts of potash that were quarried by shifting mining companies for most of the 20th century.
It is believed that Dallol, located on the main rift axis of the Danakil depression, is caused by an active basaltic volcano located under the layers of salt. The roughly circular depression on top of Dallol Mountain was suggested to be a collapse crater. The only known volcanic activity was a phreatic explosion in 1926 that produced a 30 m wide crater at the foot of the Black Mountain.