The Afar Depression is a plate tectonic triple junction where the spreading ridges that are forming the Red Sea and the Gulf of Aden emerge on land and meet the East African Rift. The Afar Depression is one of two places on Earth where a mid-ocean ridge can be studied on land, the other being Iceland. At present, the Afar is slowly being pulled apart at a rate of 1-2 cm per year. The floor of the Afar Depression is composed mostly of basaltic lava. The Afar Depression and Triple Junction also mark the location of a mantle trail, a great uprising of mantle that melts to yield basalt.
This place which used to be part of the Red Sea has kilometers of salt deposits. In some places the slat deposits are about 3miles (5 KMS) thick. Below a salt lake is a substantial source of volcanic heat which causes hot water to rise through layers of salt and a hydrate deposits. Minerals get dissolved and are deposited, near the springs, and form shapes very much reminiscent (but smaller than) hornitos on basaltic lava flows. Sulphur, other minerals and possibly Thermopylae bacteria cause spectacular colors.