Such spreading will thin a continental crust and create a region of high heat flow as is the case for the Basin and Range in Nevada. Divergent Plate Boundaries - these boundaries form where plates are breaking apart to move away from each other. The breakup of lithosphere starts in the continental portion of lithospheric plates, a process now taking place along the east Africa Rift Zone. Continental Rifts - When a supercontinent such as Pangaea breaks up, a diverging boundary can be found in the middle of a continent. In the early stages of continental breakup, the center of a continent is elevated which stretches the crust, making it thinner above the uplift.
Tension produces normal faults on either side of a rift valley which is a central graben.
Central Africa has a rift valley which is marked by high heat flow and basaltic volcanism. As divergence continues, the continental crust on the upper part of the lithospheric plate is infilled with basalt to form oceanic crust. The Red Sea, between Africa and Arabia is a narrow sea of newly formed oceanic crust. Basalt continues to erupt where heat flow is the highest between two lithospheric plates. As sea floor spreading continues, the rift valley is lifted to become the mid-ocean ridge.