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The Afar Triangle (also called the Afar Depression) is a geological depression caused by the Afar Triple Junction, which is part of the Great Rift Valley in East Africa. The region has disclosed fossil specimens of the very earliest hominins, that is, the earliest of the human clade; and it is thought by some paleontologists to be the cradle of the evolution of humans, see Middle Awash, Hadar. The Depression overlaps the borders of Eritrea, Djibouti and the entire Afar Region of Ethiopia; and it contains the lowest point in Africa, Lake Asal, Djibouti, at 155 m (or 509 ft) below sea level. The Awash River is the main waterflow into the region, but it runs dry during the annual dry season, and ends as a chain of saline lakes. The northern part of the Afar Depression is also known as the Danakil Depression. The lowlands are affected by heat, drought, and minimal air circulation, and contain the hottest places (year-round average temperatures) of anywhere on Earth. The Afar Triangle is bordered as follows (see the topographic map): on the west by the Ethiopian Plateau and escarpment; to the north-east (between it and the Red Sea) by the Danakil block; by the Somalian Plateau and escarpment to the south; and by the Ali-Sabieh block (adjoining the Somalian Plateau) to the south-east. Many important fossil localities exist in the Afar region, including the Middle Awash region and the sites of Hadar, Dikika, and Woranso-Mille. These sites have produced specimens of the earliest (fossil) hominins and of human tool culture, as well as many fossils of various flora and fauna. ==Environment== Dallol in the Danakil Depression is one of the hottest places year-round anywhere on Earth. There is no rain for most of the year; the yearly rainfall averages range from 100 to 200 millimetres (4 to 7 in), with even less rain falling closer to the coast. The climate varies from around during the very short rainy season (November–February) to during the dry season (February–November); ''see'' climate of the lowlands of the Danakil Depression. The Awash River, flowing north-eastward through the southern part of the Afar Region, provides a narrow green belt which 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 waterflow evaporates as quickly as it is supplied. Some of the Afar Depression is covered by salt deposits, and mining salt is a major source of income for many Afar groups. 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, 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 lies the Mille-Sardo Wildlife Reserve in Ethiopia. The Afar Triangle is a cradle source of the earliest hominins. It contains a paleo-archaeological district that includes the Middle Awash region and numerous prehistoric sites of fossil hominin discoveries, including: the hominids and possible hominins, Ardi, or ''Ardipithecus ramidus'', and ''Ardipithecus kadabba'', see below; the Gona (Gawis cranium) hominin; several sites of the world's oldest stone tools; Hadar, the site of Lucy, the fossilized specimen of ''Australopithecus afarensis''; and Dikika, the site of the fossilized child Selam, an australopithecine hominin. In 1994, near the Awash River in Ethiopia, Tim D. White found the then-oldest known human ancestor: 4.4 million-year-old ''Ar. ramidus''. A fossilized almost complete skeleton of a female hominin which he named "Ardi", it took nearly 15 years to safely excavate, preserve, and describe the specimen and to prepare publication of the event.〔Tim D. White, Berhane Asfaw, Yonas Beyene, Yohannes Haile-Selassie, C. Owen Lovejoy, Gen Suwa, Giday WoldeGabrie: ''Ardipithecus ramidus and the Paleobiology of Early Hominids.'' In: Science 326 (5949), 2009, pp. 75–86; PMID 19810190〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Afar Triangle」の詳細全文を読む スポンサード リンク
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