Coordinates: 11°30′N 41°00′E / 11.5°N 41.0°E / 11.5;
Location map of the
Afar Triangle (the shaded area in the center of
the map) and the
East African Rift
East African Rift zones; red triangles show
historically active volcanoes.
Topographic map showing the Afar Triangle, which correlates to the
shaded area in the location map shown above
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
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.
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.
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; to the south by the
Somalian Plateau and escarpment; and to the south-east by the
Ali-Sabieh block (adjoining the Somalian Plateau).
Many important fossil localities exist in the Afar region, including
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.
3 See also
5 External links
MODIS satellite image of the Afar Depression and surrounding regions
of the Red Sea, Gulf of Aden, Arabia, and the Horn of Africa
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 25 °C (77 °F) during
the very short rainy season (November–February) to 48 °C
(118 °F) during the dry season (February–November); see
climate of the lowlands of the Danakil Depression.
Perspective view of the Afar Depression and environs, generated by
Landsat image over a Digital elevation model.
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 128 kilometres (80 mi) from
Red Sea the Awash ends in a chain of salt lakes, where its
waterflow evaporates as quickly as it is supplied. Some 1,200 km2
(460 sq mi) of the Afar Depression is covered by salt
deposits, and mining salt is a major source of income for many Afar
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.
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
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.
See also: Afar Triple Junction
A simplified geologic map of the Afar Depression.
The Afar Depression is the product of a tectonic triple-rifts junction
(the Afar Triple Junction), where the spreading ridges forming the Red
Sea and the
Gulf of Aden
Gulf of Aden emerge on land and meet the East African
Rift. The conjunction of these three plates of Earth's crust is near
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.
Within the Triangle, 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 rift zones forming the "legs" of the triple junction. The
immediate consequences are recurring sequences of earthquakes with
deep fissures in the terrain hundreds of metres long, and the valley
floor sinking broadly across the Depression. During September and
October 2005 some 163 earthquakes of magnitudes greater than 3.9 and a
volcanic eruption occurred within the Afar rift at the Dabbahu and
Erta Ale volcanoes. Some 2.5 cubic kilometers of molten rock was
injected from below 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.
Satellite image of a graben in the Afar Depression.
Related eruptions have taken place in Teru and Aura woredas. The rift
has recently been recorded by means of three-dimensional laser
The region's salt deposits were created over time as water from the
Red Sea periodically flooded the Depression and evaporated; the most
recent such flood was roughly 30,000 years ago. Over the next
millions of years, geologists expect erosion and the
Red Sea to breach
the highlands surrounding the Afar Depression and flood the valley.
Geologists predict that in about 10 million years the whole
6,000 km length of the
East African Rift
East African Rift will be submerged,
forming a new ocean basin as large as today's Red Sea, and separating
the Somalian plate and the Horn of
Africa from the rest of the
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.
Lake Assal in Djibouti
List of fossil sites
List of fossil sites (with link directory)
List of hominini (hominin) fossils (with images)
Afar people who inhabit the region
^ "Geology of the Afar Depression". Afar
Rift Consortium. Retrieved 27
^ Shreeve, Jamie (July 2010). "The Evolutionary Road". National
Geographic. Washington, D.C.: National Geographic Society.
ISSN 0027-9358. Retrieved 2015-05-28.
^ White, Tim D.; Asfaw, Berhane; Beyene, Yonas; Haile-Selassie,
Yohannes; Lovejoy, C. Owen; Suwa, Gen; WoldeGabrie, Giday (2009).
Ardipithecus ramidus and the Paleobiology of Early Hominids".
Science. 326 (5949): 75–86. Bibcode:2009Sci...326...75W.
doi:10.1126/science.1175802. PMID 19810190.
^ Beyene, Alebachew & Abdelsalam, Mohamed G. (2005). "Tectonics of
the Afar Depression: A review and synthesis". Journal of African Earth
Sciences. 41 (1–2): 41–59. Bibcode:2005JAfES..41...41B.
^ Wright, TJ; Ebinger, C; Biggs, J; Ayele, A; Yirgu, G; Keir, D;
Stork, A (July 2006). "Magma-maintained rift segmentation at
continental rupture in the 2005 Afar dyking episode". Nature. 442
(7100): 291–294. Bibcode:2006Natur.442..291W.
doi:10.1038/nature04978. PMID 16855588.
^ "Inside the Hottest Place on Earth". BBC News. 2009-03-19. Retrieved
August 30, 2009.
^ Hottest Place On Earth, Episode 1 at bbc.co.uk Archived November 14,
2012, at the Wayback Machine.
^ Morell, Virginia (January 2012). "Hyperactive Zone". National
Geographic. 221 (1): 116–127.
^ Bojanowski 2006
^ Hammond, J. O. S., J.- M. Kendall, G. W. Stuart, C. J. Ebinger, I.
D. Bastow, D. Keir, A. Ayele, M. Belachew, B. Goitom, G. Ogubazghi,
and T. J. Wright. "Mantle Upwelling and Initiation of Rift
Segmentation beneath the Afar Depression." Geology 41.6 (2013):
Barberi, F.; Borsi, S.; Ferrara, G.; Marinelli, G.; Santacroce, R.;
Tazieff, H.; Varet, J. (1972). "Evolution of the Danakil Depression
(Afar, Ethiopia) in Light of Radiometric Age Determinations". Journal
of Geology. 80 (6): 720–729. Bibcode:1972JG.....80..720B.
Bojanowski, Axel (2006-03-15). "Africa's New Ocean: A Continent Splits
Apart". Spiegel Online. Retrieved 2006-03-16. Includes a photo
essay of the region and its geologic changes.
Kloos, Helmut (1982). "Development, drought and famine in the Awash
valley of Ethiopia". African Studies Review. 25 (4): 21–48.
doi:10.2307/524399. JSTOR 524399.
"Ethiopian xeric grasslands and shrublands". Terrestrial Ecoregions.
World Wildlife Fund.
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
Jeangene Vilmer, Jean-Baptiste; Gouery, Franck (2011). Les Afars
d'Éthiopie. Dans l'enfer du Danakil. ISBN 9782352701088.
Archived from the original on 2013-07-31.
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