The Danakil Depression is the northern part of the Afar Triangle or Afar Depression in Ethiopia, a geological depression that has resulted from the divergence of three tectonic plates in the Horn of Africa.
The Danakil Depression lies at the triple junction of three tectonic plates and has a complex geological history. It has developed as a result of Africa and Asia moving apart, causing rifting and volcanic activity. Erosion, inundation by the sea, the rising and falling of the ground have all played their part in the formation of this depression. Sedimentary rocks such as sandstone and limestone are unconformably overlain by basalt which resulted from extensive lava flows.
The Danakil Depression is a plain, some 200 by 50 km (124 by 31 mi), lying in the north of the Afar Region of Ethiopia, near the border with 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. This area is referred to as the cradle of hominids after Donald Johanson and his colleagues in 1974 found the famous Australopithecus fossil Lucy, which has been dated 3.2 million years old.
The Danakil Depression is the hottest place on Earth in terms of year-round average temperatures. It is also one of the lowest places on the planet (100 m below sea level), and without rain for most of the year. Here, the Awash River dries up in a chain of salt lakes such as Lake Afrera, never reaching the Indian Ocean.
Mount Ayalu is the westernmost and older of the two volcanoes at the southern end of the Danakil Depression. The other active volcano, Erta Ale, is one of several crater lakes of lava bubbling from the Earth's mantle. Additionally, the area contains the Dallol sulfur springs, or hot springs. These wet environments at the Danakil Depression are being investigated to help understand how life might arise on other planets and moons. Any microorganisms living here will be extremophilic microbes of a major interest to astrobiologists.
Among the geological points of interest to tourists are several hot springs, among them Yellow Lake.