East African Rift
A continental rift zone stretching from the Afar Triple Junction to Mozambique, where the African plate is slowly splitting apart.
Afar Triple Junction: The junction in Ethiopia where the Red Sea, Gulf of Aden and East African Rift boundaries meet. The point where the rift branches off from the already-oceanic spreading ridges.
Miocene: The epoch from 23 to 5.3 million years ago, marked by grassland spread and ape evolution. Rifting began in Ethiopia and Kenya during the Early Miocene, around 25 million years ago.
Lake Tanganyika: The world's second-deepest lake, filling a 1,470-metre-deep fault trough in the western rift arm. Its depth records how much the western branch has subsided.
Out of Africa: The dispersal of anatomically modern humans from Africa beginning around 60,000 years ago. Rift corridors are proposed as routes along which early hominins expanded.
Mid-Atlantic Ridge: The undersea spreading boundary separating the American plates from Eurasia and Africa. A mature mid-ocean ridge versus the rift's on-land incipient spreading.
Rift valley: A long, sunken block of crust bounded by normal faults, formed where land is being pulled apart. The fault-bounded troughs of Kenya and Ethiopia are the rift's visible structure.
Red Sea: A young ocean basin between Africa and Arabia that opened as the Arabian plate rifted away. The Red Sea shows what the East African Rift becomes after continental breakup succeeds.
Ol Doinyo Lengai: A Tanzanian volcano erupting natrocarbonatite, the coolest, most fluid lava known on Earth. Its unique carbonatite lava reflects the rift's unusual magmatic chemistry.
Savanna hypothesis: The idea that drying, open landscapes drove hominin walking and toolmaking evolution. Rift formation changed East African landscapes during the span of human evolution.
Western Rift: The western branch of the East African Rift, curving through the Great Lakes and volcanically quieter. Its deep fault-bound lakes differ from the volcanic eastern branch.