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How do rift valleys form along divergent tectonic plate boundaries?
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The rugged Atlas Mountains surround a valley in Morocco.
A rift valley is an elongated trough formed by the subsidence of the Earth's crust between normal faults, where rock material is displaced downward. These features occur at divergent plate boundaries, where lithospheric plates move away from each other.1
The formation process involves several stages:
- Uplift and Stretching: Upwelling magma causes the overlying lithosphere to uplift and stretch.2
- Fracturing: As the plates diverge, fractures develop in the crust. These are often invaded by ascending magma, which helps pry the continental blocks apart.2
- Subsidence: The settling of these continental blocks creates the characteristic rift valley.2
- Evolution: If the process continues, the crust thins until the plates separate entirely. New oceanic crust forms as magma cools, eventually leading to the development of an oceanic ridge and the creation of a new ocean basin.2
While continental rift valleys represent sites of incipient spreading, numerous submarine rift valleys exist along the crests of oceanic ridges, where seafloor spreading is actively occurring.13