Cooler, older, oceanic lithosphere sinks into the mantle at cooler, older, oceanic lithosphere sinks into the mantle at rift zones along oceanic ridges subduction zones along convergent plate boundaries sites of long-lived, hot spot volcanism in the ocean basins transform fault zones along divergent plate boundaries

submerging rift zone due to slab pull

Explanation:

It is a low lying area found on both land and seas of oceanic ridges subduction zones along the convergent plate boundaries which are sited for long-lived hot spots in volcanic ocean basins and transforms faults are a result of divergent boundaries. As the older and denser rocks sink deeper into the mantel and fall along the zone of hot spots. Grabens being an example of a rift valley on land is the center of mega-earthquake going deep down to the center of the mantel. Overplayed by the lighter and less dense material or the slabs made up of silicon layers. Impacted by slab push and pull. This process has its history with the isostatic movements of the earth as the earth keeps in balance the cycle of geomaterials.

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