The Afar Depression

The Jebel Qatrani

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EUGENE M. MCCARTHY, PHD
afar depression map

The Afar Depression (shaded and at center in the map above) is a triple junction, where three plates are pulling away from each another: the Arabian Plate, and the two parts of the African Plate (the Nubian and the Somalian) splitting along the East African Rift Zone. The Afar contains Ethiopia's Middle Awash. The region adjacent to this river has yielded numerous important hominid finds.

volcano
The volcano Erta Ale lies in the desert region of the Afar Depression. The most active volcano in Ethiopia, it's topped by a permanent lake of lava, one of only four volcanoes worldwide with this feature.

The Afar Depression (also called the Danakil Depression or the Afar Triangle) is a geological depression formed by the junction of the East African Rift with the two spreading ridges that have formed the Red Sea and the Gulf of Aden. It lies near the Horn of Africa, overlapping Eritrea, Djibouti, and the Afar Region of Ethiopia.

In the depression, along each of the three rifts, the Earth's crust is spreading apart at an annual rate of about 0.3–0.8 inches (1–2 centimeters). There are many deep fissures in the ground and small earthquakes occur in this region on an almost continuous basis. It's one of two places on Earth where a spreading ridge, such as those normally found in the middle of the world's oceans, can be studied on land (the other being Iceland).

The Afar Depression contains the Middle Awash Valley, a region that has yielded many fossil hominid discoveries (in particular, Ardipithecus ramidus, Ardipithecus kadabba, and Australopithecus garhi); the Kada Gona river valley, site of discovery of the oldest stone tools known, which date to about 2.5 mya (Semaw et al. 1997, Semaw 2000); and Hadar, where Lucy, the best-known specimen of Australopithecus afarensis was found.

In addition, the Awash Valley is the site of a much-studied contact zone between the olive baboon (Papio anubis) and the hamadryas baboon (Papio hamadryas), where these two baboons hybridize on an ongoing basis (Kawai and Sugawara 1976a; Nagel 1973; Phillips-Conroy 1978; Newman 1997; Shotake 1981; Newman 1997; Shotake et al. 1977; Sugawara, K. 1979, 1982).

The Afar Depression derives its name from the Afar people, who live there. Their language is also known as Afar.

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