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How are rift valleys different from river valleys?
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tectonic basins and rift valleys
Escarpments of the Great Rift Valley rising above the plain north of Samburu Game Preserve, central Kenya. Beisa oryxes graze in the foreground.
The primary difference between rift valleys and river valleys lies in their origin: rift valleys are produced by tectonic activity, whereas the vast majority of river valleys are created by erosional forces.12
- Rift Valleys: These are tectonic depressions formed by the extension of the Earth’s crust. As lithospheric plates diverge, a block of crust—known as a graben—subsides between normal faults. These valleys are characterized by steep, mountainous sides and relatively flat floors, and they often exist as a low topographic zone before any river occupies them.312
- River Valleys: In contrast, most river valleys are formed by the rivers themselves, which carve the landscape through erosion over time. In these cases, the valley's characteristics and morphology are a direct result of the river's flow and its capacity to entrain sediment.2
While some rivers, such as the Jordan River, may occupy a pre-existing rift valley, the fundamental distinction remains that rift valleys are products of crustal displacement, while river valleys are products of surface erosion.12