The Danakil Desert is located between the Ethiopian plateau and the Red Sea. The salt plain near Dallol is the lowest part at 116 metres below sea level.
In prehistoric times, the territory was in the form of a gulf. According to geologists, this is a sea bed that emerged for a brief moment in the history of the planet; the Afar depression will in fact form a future ocean with the Red Sea and the Gulf of Aden.
This geological anomaly means that the entire area is very unstable. There are numerous active volcanoes and frequent earthquakes, /together with secondary manifestations such as the stupendous colours of the salt surfaces, caused by the geysers with their various different chlorides.
This inhospitable territory is home to nomadic sheep-herding Afar people.
This tribe has a strong sense of its own identity and enjoys a notable degree of autonomy in its land. The Afar live from their animals, agriculture and the sale of salt that they extract from the salt lakes of the Danakil depression. The salt is loaded onto camels and sold in the markets of the highlands.
Erta Ale, the living Shield Volcano
Location: Lat. 13.6N, Long. 40.7EElevation: 2,011 feet (613 m)
Erta Ale is a very remote and rarely visited shield volcano in the Afar region of East Africa. It is Ethiopia's most active volcano and it has been in a state of continuous eruption since 1967. Daytime temperatures will likely be above 40 degrees Celcius and the base of the volcano actually lies below sea level and it's summit rises up to 613 Meters. Erta Ale is known for it's 2 pit craters which have had active lava lakes in the past.
Erta Ale has undergone seven eruption events in the past 125 years. Three of the early eruption dates, 1873, 1903, and 1904 are uncertain. However, 1906, 1940, 1960, and 1967 are well established events. Erta Ale has been erupting continuously since 1967.
Two new studies on Erta Ale have recently been published. Oppenheimer and Francis (1998) looked at the implications of long-lived lava lakes. They believe that Erta Ale's lava lake has been active for at least the last 90 years (making it one of the longest known historic eruptions). Large amounts of heat are released by the volcano but the amount of lava that erupts is relatively small. Oppenheimer and Francis speculated that a higher magma density (caused by the cooling of the lava in the lake) inhibits eruptions. They proposed that most of the magma accumulates in the underlying crust in the form of dikes and sills. Since the Afar region is under extension, conditions are favorable for the injection of dikes and sills.
Barrat and others (1998) looked at the chemistry of the rocks at Erta Ale. Rocks range in composition from basalt to rhyolite. Barrat and others found that two mantle sources were tapped for the basalts: one similar in composition to the source for mid-ocean ridge basalts (called MORB by geochemists) and one similar in composition to the source for ocean-island basalts (called OIB). Their data did not show a significant contribution of sialic material from the continental crust. The silica-rich volcanics are derived from fractional crystallization of basaltic magmas.
