Move away from each other (DIVERGENT PLATE)
When the two plates move away from each others. As the plate moves apart, the rocks break and form fractures in the crust when an earthquake occur along the plate boundary. Magma from the mantle rises to the ocean floor through these fractures and solidifies at the plate boundary, form new crust. The boundaries where the plates move apart are described as “CONSTRUCTIVE PLATE BOUNDARIES” because new crust is being formed and added to the ocean floor. As the result, the ocean floor gradually extends and increases in size.This will make the sea floor spreading and extended the Oceanic ridges. Oceanic ridges is form when the magma continues to rise on the ocean floor and piles up and solidifies forming a long chain of mountains on the ocean floor.