What marks the seaward edge of the continental shelf? (next zone as we move out from land)

continental rise

Explanation:

In nearly all instances, it ends at its seaward edge with an abrupt drop called the shelf break. Below this lies the continental slope, a much steeper zone that usually merges with a section of the ocean floor called the continental rise at a depth of roughly 4,000 to 5,000 metres

heat from the core of the earth causes convection currents to occur in the mantle. these currents slowly move the crust around.