<P> A rift valley is a linear - shaped lowland between several highlands or mountain ranges created by the action of a geologic rift or fault . A rift valley is formed on a divergent plate boundary , a crustal extension , a spreading apart of the surface , which is subsequently further deepened by the forces of erosion . When the tensional forces were strong enough to cause the plate to split apart , a center block dropped between the two blocks at its flanks , forming a graben . The drop of the center creates the nearly parallel steeply dipping walls of a rift valley when it is new . That feature is the beginning of the rift valley , but as the process continues , the valley widens , until it becomes a large basin that fills with sediment from the rift walls and the surrounding area . One of the best known examples of this process is the East African Rift . On Earth , rifts can occur at all elevations , from the sea floor to plateaus and mountain ranges in continental crust or in oceanic crust . They are often associated with a number of adjoining subsidiary or co-extensive valleys , which are typically considered part of the principal rift valley geologically . </P>
<P> A rift valley is a linear - shaped lowland between several highlands or mountain ranges created by the action of a geologic rift or fault . A rift valley is formed on a divergent plate boundary , a crustal extension , a spreading apart of the surface , which is subsequently further deepened by the forces of erosion . When the tensional forces were strong enough to cause the plate to split apart , a center block dropped between the two blocks at its flanks , forming a graben . The drop of the center creates the nearly parallel steeply dipping walls of a rift valley when it is new . That feature is the beginning of the rift valley , but as the process continues , the valley widens , until it becomes a large basin that fills with sediment from the rift walls and the surrounding area . One of the best known examples of this process is the East African Rift . On Earth , rifts can occur at all elevations , from the sea floor to plateaus and mountain ranges in continental crust or in oceanic crust . They are often associated with a number of adjoining subsidiary or co-extensive valleys , which are typically considered part of the principal rift valley geologically . </P>
a rift valley is evidence of which kind of plate boundary
a rift valley is evidence of which kind of plate boundary
a divergent plate boundary
a divergent plate boundary