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 Location of the triangle (the shaded area in the center of the map) and the local fault lines. The Afar Triangle (also called the Afar Depression or the Danakil Depression) is a geological depression that is caused by the Afar Triple Junction which is part of the Great Rift Valley. It overlaps Eritrea, Djibouti and the entire Afar Region of Ethiopia. The Afar Triangle includes the Danakil Depression and the lowest point in Africa, Lake Asal ( below sea level). Only the Awash River flows into the area, where it ends in a chain of lakes that increase in salinity. Dallol is also part of the depression, one of the hottest places year-round anywhere on Earth. The climate varies from around during the rainy season (September March) to during the dry season (March September). Afar is well known as one of the cradles of hominids, containing the Middle Awash, site of many fossil hominid discoveries such as Ardi, (Ardipithecus ramidus); the Gona (Gawis cranium), site of the world's oldest stone tools; and Hadar, site of Lucy, the fossilized specimen of Australopithecus afarensis.
Environment The lowlands of the Afar Depression are affected by heat and drought. There is no rain for most of the year, and yearly rainfall averages range from 100 to 200 millimetres (4 to 7 in), with less rain falling closer to the coast. The Awash River, flowing north-eastward through southern Afar, provides a narrow green belt and enables life for the flora and fauna in the area and for the Afars, the nomadic people living in the Danakil desert. About from the Red Sea, the Awash ends in a chain of salt lakes, where its water evaporates as quickly as it is supplied. About of the Afar Depression is covered by salt, and salt mining is still a major source of income for many Afar tribes. The Afar Depression biome is characterized as desert scrubland. Vegetation is mostly confined to drought-resistant plants such as small trees (e.g. species of the dragon tree), shrubs, and grasses. Wildlife includes many herbivores such as Grevy's Zebra, Soemmering s Gazelle, Oryx Beisa and, notably, the last viable population of African wild ass (Equus africanus somalicus). Birds include the ostrich, the endemic Archer's lark (Heteromirafra archeri), the Secretary Bird, Arabian and Kori bustards, Abyssinian Roller and Crested Francolin. In the southern part of the plain, in Ethiopia, lies the Mille-Sardo Wildlife Reserve (established 1973). Many fossils have been found in the Awash region, not only hominids but also elephantoids, crocodiles and hippopotamus. Geology Simplified geologic map of the Afar Depression. Satellite image of a graben in the Afar Depression. The Afar Depression is the product of a tectonic triple junction (the Afar Triple Junction), where the spreading ridges that form the Red Sea and the Gulf of Aden emerge on land and meet the East African Rift. The central meeting place for these three pieces of Earth's crust is around Lake Abbe. The Afar Depression is one of two places on Earth where a mid-ocean ridge can be studied on land, the other being Iceland. In the Depression, the Earth's crust is slowly rifting apart at a rate of 1 2 centimetres (0.4 0.8 in) per year along each of the three rifts which form the "legs" of the triple junction. The immediate consequence of this is that there are () a continuous sequence of earthquakes, fissures hundreds of metres long and deep appearing in the ground, and the valley floor sinking as much as 100 metres. Between September and October 2005, 163 earthquakes of magnitudes greater than 3.9 and a volcanic eruption occurred within the Afar rift at the Dabbahu and Erta Ale volcanoes. 2.5 cubic kilometers of molten rock was injected into the plate along a dyke between depths of 2 and 9 km, forcing open an 8 meter wide gap on the surface, known as the Dabbahu fissure.[1][2] Related eruptions have taken place in Teru and Aura woredas. The rift has recently been recorded by means of three-dimensional laser mapping.[3] The salt deposits which local people mine for income were created, over the course of history, as water from the Red Sea periodically flooded the Depression and evaporated; the most recent such flood was roughly 30,000 years ago.[4] Over millions of years, geologists expect the Red Sea to erode through the highlands surrounding the Afar Depression and flood the valley. In about 10 million years, geologists predict that the whole 6,000 km length of the East African Rift will be submerged, forming a new sea as large as the Red Sea is now, and separating the Horn of Africa from the rest of the continent.[5] The floor of the Afar Depression is composed of lava, mostly basalt. One of Earth's five lava lakes, Erta Ale is found here, as well as Dabbahu Volcano. It has been proposed that the Afar Depression is underlain by a mantle plume, a great upwelling of mantle that melts to yield basalt as it approaches the surface. See also References Notes Bibliography - Includes a photo essay of the region and its geologic changes.
- Jon Kalb: Adventures in the Bone Trade. The Race to Discover Human Ancestors in Ethiopia's Afar Depression. Copernicus Books, New York 2001, ISBN 0-387-98742-8
External links ar: bg: ( ) de:Afar-Dreieck es:Depresi n de Afar fr:D pression de l'Afar hi: hr:Afarski trokut id:Depresi Afar it:Triangolo di Afar he: lt:Danakili duba hu:Afar-medence ms:Lekukan Afar nl:Danakildepressie ja: nn:Afarsenkinga pl:Kotlina Danakilska pt:Tri ngulo de Afar ro:Depresiunea Afar ru: sh:Afarska depresija fi:Afarin syv nk sv:Afartriangeln uk:
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