Continental rifting

Continental rifting is the stretching and thinning of continental lithosphere, driven by tectonic forces. It can develop into seafloor spreading and divide a continent into separate plates.

Lithospheric stretching: Tectonic extension lengthens and thins the lithosphere, often measured by comparing its initial and final thickness. It is the basic deformation that initiates continental rifting.
East African Rift: An active system of rift valleys and faults extending through eastern Africa. It is a major present-day example of continental extension.
Plate tectonics: The theory that Earth’s lithosphere is divided into moving plates whose interactions shape the planet’s surface. Continental rifting is one way plate boundaries develop and reorganize.
Active rifting: A rifting model in which mantle upwelling initiates lithospheric extension. It contrasts with models that place the initial cause in plate-driven stretching.
Passive margin: A continental edge that is not an active boundary between tectonic plates. A successful rift can leave a passive margin after oceanic crust forms.
Normal fault: A fault on which the hanging wall moves downward relative to the footwall as the crust extends. Normal faults accommodate much of the brittle extension in rift zones.
Afar Depression: A low-lying region in northeastern Africa where the Red Sea, Gulf of Aden, and East African rift systems meet. Its unusually thin crust and active volcanism expose the transition toward oceanic spreading.
Divergent boundary: A plate boundary at which two tectonic plates move apart. A rift may become a divergent boundary as extension separates continental blocks.
Passive rifting: A rifting model in which plate forces stretch the lithosphere and mantle rises in response. It reverses the proposed causal order of mantle upwelling and extension.
Continental breakup: The final separation of continental lithosphere into distinct plates, commonly accompanied by new oceanic crust. It marks the point at which rifting produces separate plates.

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