Answer:
Seafloor spreading
Step-by-step explanation:
Seafloor spreading -
It is the method which happens at the mid - ocean ridges , where the new oceanic crust is made via some volcanic eruption and then slowly moves away from the ridge , is known as seafloor spreading.
The convection current beneath the seafloor pushes the magma outwards , and thereby forcing the older material away and new material comes and form a fresh new seafloor.