Afar Triangle in the context of Geological depression

The Sultanate of Aussa was a kingdom that existed in the Afar Triangle in southern Eritrea, eastern Ethiopia and western Djibouti from the 18th to the 20th century. It was considered to be the leading monarchy of the Afar people, to whom the other Afar rulers nominally acknowledged primacy.

Throughout the region’s history the Afar were lauded as great warriors whose slaying was held in higher regard than that of the Oromos to the soldiers of the Kingdom of Shewa. The expanding Ethiopians laid claim to the region but were met with harsh resistance due to the Afar's skills in desert warfare and that the Abyssinians were a highlander people "unsuited by nature to operations in these hot and feverish lowlands - To subdue them would indeed prove no easy task, taking into consideration the waterless nature of their country away from the (Awash River) river, and the unhealthy conditions prevalent along its banks." Due to this, and more, the Danakil country managed to remain independent from the Khedivate of Egypt and autonomous within the later Ethiopian Empire, unlike other (similar) groups in the region and the previous Dankali Sultanate.

The East African Rift (EAR) or East African Rift System (EARS) is an active continental rift zone in East Africa. The EAR began developing around the onset of the Miocene, 22–25 million years ago. It is considered to be part of a larger system, formerly known as the Great Rift Valley, that extends north to Asia Minor.

A narrow zone, the rift is a developing divergent tectonic plate boundary where the African plate is in the process of splitting into two tectonic plates, called the Somali plate and the Nubian plate, at a rate of 6–7 mm (0.24–0.28 in) per year. The rift system consists of three microplates, the Victoria microplate to the north, and the Rovuma and Lwandle microplates to the south. The Victoria microplate is rotating anti-clockwise with respect to the African plate. Its rotation is caused by the configuration of mechanically weaker and stronger lithospheric regions in the EARS.

In geology, a graben (/ˈɡrɑːbən/) is a depressed block of the crust of a planet or moon, bordered by parallel normal faults.

The Afar triple junction is a triple junction located along a divergent plate boundary dividing the Nubian, Somali, and Arabian plates. This area is considered a present-day example of continental rifting leading to seafloor spreading and producing an oceanic basin. Here, the Red Sea Rift meets the Aden Ridge and the East African Rift. The latter extends a total of 6,500 kilometers (4,000 mi) from the Afar Triangle to Mozambique.

The connecting three arms form a triple junction. The northernmost branching arm extends north through the Red Sea and into the Dead Sea, while the eastern arm extends through the Gulf of Aden and connects to the Mid-Indian Ocean ridge further to the east. Both of these rifting arms are below sea level and are similar to a mid-ocean ridge.

Lake Assal (Arabic: بحيرة عسل Buḥayrah ʿAsal, lit. “Honey Lake”) is a crater lake in central-western Djibouti. It is located at the western end of Gulf of Tadjoura between Arta Region, and Tadjoura Region, touching Dikhil Region, at the top of the Great Rift Valley, some 120 km (75 mi) west of Djibouti city. Lake Assal is a saline lake that lies 155 m (509 ft) below sea level in the Afar Triangle, making it the lowest point on land in Africa and the third-lowest point on Earth after the Sea of Galilee and the Dead Sea. No outflow occurs from the lake, and due to high evaporation, the salinity level of its waters is 10 times that of the sea, making it the fifth most saline body of water in the world, behind Garabogazköl, Lake Retba, Gaet'ale Pond and Lake Elton. The salt in the lake is exploited under four concessions awarded in 2002 at the southeast end of the lake; the major share of production (nearly 80%) is held by Société d’Exploitation du Lac and Société d’Exploitation du Salt Investment S.A de Djibouti.

The lake is a protected zone under Djibouti's National Environmental Action Plan of 2000. However, the law does not define the boundary limits of the lake. Since the exploitation of the salt from the lake was uncontrolled, the Plan has emphasized the need for managing the exploitation to avoid negative impact on the lake environment. The Government of Djibouti has initiated a proposal with UNESCO to declare the Lake Assal zone and the Ardoukoba volcano as a World Heritage Site.

Herto Man refers to human remains (Homo sapiens) discovered in 1997 from the Upper Herto member of the Bouri Formation in the Afar Triangle, Ethiopia. The remains have been dated as between 154,000 and 160,000 years old. The discovery of Herto Man was especially significant at the time, falling within a long gap in the fossil record between 300 and 100 thousand years ago and representing the oldest dated H. sapiens remains then described.

In the original description paper, these 12 (at minimum) individuals were described as falling just outside the umbrella of "anatomically modern human". Thus, Herto Man was classified into a new subspecies as "Homo sapiens idaltu" (Afar: Idaltu "elder"). It supposedly represented a transitional morph between the more archaic H. (s.?) rhodesiensis and H. s. sapiens (that is, a stage in a chronospecies). Subsequent researchers have rejected this classification. The validity of such subspecies is difficult to justify because of the vague definitions of "species" and "subspecies", especially when discussing a chronospecies, as the exact end-morphology and start-morphology of the ancestor and descendant species are inherently unresolvable.

The Danakil Depression is a large valley of approximately 200 by 50 km (124 by 31 mi), across the north of the Afar Region of Ethiopia and Eritrea. It is about 125 m (410 ft) below sea level and is bordered to the west by the Ethiopian Plateau and to the east by the Danakil Alps, beyond which is the Red Sea. It is the third lowest-lying location on the continent of Africa.

The Danakil Depression is a geological depression formed by rifting. It constitutes the northern part of the Afar Triangle or Afar Depression.

The Afar Region (/ˈɑːfɑːr/; Afar: Qafar Rakaakayak; Amharic: ዓፋር ክልል), formerly known as Region 2, is a regional state in northeastern Ethiopia and the homeland of the Afar people. Its capital is the planned city of Semera, which lies on the paved Awash–Assab highway. It is bordered by Eritrea to the north and Djibouti to the northeast; it also shares regional borders with the Tigray, Amhara, Oromo and Somali regions.

The Afar Triangle, the northern part of which is the Danakil Depression, is part of the Great Rift Valley of Ethiopia, and is located in the north of the region. It has the lowest point in Ethiopia and one of the lowest in Africa. The southern part of the region consists of the valley of the Awash River, which empties into a string of lakes along the Djibouti–Ethiopia border. Other notable landmarks include the Awash National Park.

The Bouri Formation is a sequence of sedimentary deposits that is the source of australopithecine and Homo (that is, hominin) fossils, artifacts, and bones of large mammals with cut marks from butchery with tools by early hominins. It is located in the Middle Awash Valley, in Ethiopia, East Africa, and is a part of the Afar Depression that has provided rich human fossil sites such as Gona and Hadar.

The Bouri Formation stretches down much of the length and breadth of the Bouri "peninsula", which projects across the dry bed of the Afar Depression. The Formation is sufficiently eroded to expose three geological members or layers: the Hatayae, the Dakanihylo, and the Herto. Human remains with signs of having been prepared for burial have been found in the Upper Herto layers.