Afar triangle
Coordinates: 12 ° N , 41 ° E
The Afar Triangle (also Afar Depression or Danakil Depression ) is a lowland plain in East Africa . It is bounded by the highlands of Ethiopia in the west, the Somali highlands in the south, and the Bab al-Mandab strait , which connects the Red Sea with the Gulf of Aden .
The approximately 175,000 square kilometer area measures around 700 km from north to south and around 500 km from west to east. Politically, it includes Djibouti , the Afar region in Ethiopia , and areas of Eritrea and Somalia . Its name is derived from the Afar or Danakil people who live there .
As the area lies in the lee of the Ethiopian highlands, it has very little rainfall.
geology
From a geological point of view, the Afar Triangle is unique because three active rift breaks meet there . The north-northwestern rift valley lies between the region and the Red Sea , and a second lies between the region and the northeastern Gulf of Aden . Third, the East African Rift, which runs south, lies here . Here the earth's crust is expanding as a result of the continental drift and all three rift breaks are still active. The tectonic plates on the respective flanks of the rift breaks diverge. In the case of the Gulf of Aden adjoining the Red Sea, an ocean basin as we know it today will probably develop in the future.
Volcanism
In the depression there are numerous volcanoes such as the Erta Ale , Dallol , Borawli , Adwa , Afdera , Alayta , Alid , Dabbahu and Nabro .
depression
As a result of this expansion, the earth's crust becomes considerably thinner and therefore sinks. In the Afar Triangle, this expansion has been going on for 30 million years, and due to this geological activity, large parts of the area are now up to 125 m below sea level , thus forming a depression . Examples of this are the Danakil Depression in Eritrea (−110 m; cf. Danakil Somalia ), the Koba Depression in Ethiopia (−115 m) and the salt lakes mentioned below.
Various rivers such as the Awash end here and form (salt) lakes such as Lake Abbe , Lake Assal , Lake Karum , Lake Bakili and Lake Afrera . The salt from these deposits is also traditionally used in Ethiopia as a means of payment ( amole ).
According to calculations by geologists, the extensive sinking of the Afar triangle can still be expected; one day the depression will be completely filled with water from the Red Sea . Geological activities in the region have increased significantly since 2005. If there were movements in the millimeter range before, gaps in the meter range were most recently created. Volcanic activity is also increasing above and below ground.
paleontology
The Afar Triangle became known worldwide in 1974 after Donald Johanson found the very well preserved fossil of a 3.18 million year old Australopithecus afarensis named after this region , called " Lucy " in Hadar . From this fossil species - or a close relative of this species - the genus Homo has developed according to the current state of paleanthropological research , to which all modern humans ( Homo sapiens ) are assigned. From 1994 to 1997 the remains of “ Ardi ”, a largely preserved fossil of Ardipithecus ramidus , were also found in the Middle Awash area , only a few kilometers from “Lucy” . This 4.4 million year old find is considered to be the best preserved fossil from the circle of the earliest hominini . The well-preserved fossil DIK 1-1 also comes from Dikika , and in 2012, with the Burtele foot recovered in the Woranso-Mille excavation area, references to a species that have not yet been named were published.
The oldest stone tools of the African Early Stone Age ( Oldowan culture) come from the Gona site near Hadar; they are 2.6 to 2.5 million years old. In 2009, 3.3 million year old scratches and cuts from stone tools on fossil animal bones were discovered at Dikika , which prove, among other things, that Australopithecus afarensis already scratched meat from rib and leg bones. Because of this large number of finds, the Afar triangle is considered to be one of the cradles of mankind .
The extensive Afar Depression has fossil-bearing sediment fillings from the Miocene to the Holocene . In total, the fossil-bearing layers are more than 1000 meters thick. The lowest layers have been dated to an age of six million years on the basis of volcanic rock, in the upper, 155,000 year old layers, early evidence of the archaic Homo sapiens was found.
The area was repeatedly deeper than it is today and was inundated by rivers, but then raised again and fell dry. Large quantities of prehistoric fish, turtle and crocodile remains have been found in the sediments of earlier floodplains and lakes. Bones of the ancestors of elephants, hippopotamuses, antelopes, giraffes, pigs, horses, rhinos, lions, hyenas and various species of monkeys have been discovered in the deposits of long-gone rivers - and the remains of early ancestors of modern humans have been discovered again and again . The finds are kept in the National Museum of Ethiopia in Addis Ababa , where they are also scientifically evaluated by international research teams .
literature
- 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 .
- Ottmar Kullmer: Expeditions to the Afar Triangle. Search for fossils under the Ethiopian sun. In: Nature and Museum. The Senckenberg nature magazine. Volume 135, No. 3/4. SGN, Frankfurt am Main 2005, ISSN 0028-1301 , pp. 58-67.
- Ian D. Bastow, Derek Keir: The protracted development of the continent-ocean transition in Afar. In: Nature Geoscience , Volume 4, pp. 248-250, 2011, doi : 10.1038 / ngeo1095
- W (ilmos) v (on) Zichy: The Danakil Coast . In: Ernst Behm : Dr. A. Petermann's communications from Justus Perthes' Geographical Institute . Volume 26.1880, ZDB -ID 2656552-3 . Perthes, Gotha 1880, pp. 133-136. - Full text online .
- Uwe George (report and photos): Birth of an ocean . In: Geo-Magazin. Hamburg 1978, 7, pp. 50-80. ("Uwe George witnessed the first phase of a process that took millions of years: Africa is breaking apart in the Rift Valley.") (The Afar triangle shows this clearly) ISSN 0342-8311
Web links
- esa aerial photo of the Afar triangle
- Map of the Afar region (PDF, 154 kB)
- Geologists observe the birth of an ocean ( memento from September 29, 2007 in the Internet Archive ) Netzeitung
- Before the birth of a new inlet faz.net, April 2, 2011
Individual evidence
- ↑ Axel Bojanowski : Surprising eruptions - volcanic inferno creates new ocean in Africa , Spiegel Online, January 19, 2011
- ↑ S. Semaw et al .: 2.5-million-year-old stone tools from Gona, Ethiopia. In: Nature , Volume 385, 1997, pp. 333-336, doi : 10.1038 / 385333a0
- ↑ Shannon P. McPherron et al .: Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikika. In: Nature , Volume 466, 2010, pp. 857-860, doi : 10.1038 / nature09248
- ↑ Giday Wolde-Gabriel et al .: The Geological, Isotopic, Botanical, Invertebrate, and Lower Vertebrate Surroundings of Ardipithecus ramidus. Science, Volume 326, 2009, p. 65, doi : 10.1126 / science.1175817
- ↑ Ernesto Abbate, Andrea Albianelli, Augusto Azzaroli et al .: A one-million-year-old Homo cranium from the Danakil (Afar) Depression of Eritrea. In: Nature. Volume 393, 1998, pp. 458-460, doi: 10.1038 / 30954