What causes seafloor spreading?

Sea-floor spreading is what happens at the mid-oceanic ridge where a divergent boundary is causing two plates to move away from one another resulting in spreading of the sea floor. As the plates move apart, new material wells up and cools onto the edge of the plates.

Seafloor spreading happens at the mid-ocean ridge where the divergent boundary is causing the two plates to move from each other. As the plates move apart new material wells up and cools at the edge of the plate.

Divergent Boundary - linear feature that is between two plates that are moving