Mid-oceanic ridge is a long mountain range on the ocean floor, extending almost continuously through the North and South Atlantic Oceans, the Indian Ocean, and the South Pacific Ocean. A deep rift valley is located at its center, from which magma flows and forms new oceanic crust. As the magma cools and hardens it becomes part of the mountain range. Mid-oceanic ridges form when tectonic plates meet beneath the ocean and ridge-push, slab-pull or do both to create a subduction zone. See Also :