Answer:
Rocks deteriorating the ocean floor
Step-by-step explanation:
As rocks scrape past the ocean floor they chip away at it smoothing it (erosion) out but due to continental drift and magma rising and cooling it causes the new igneous rock forms on the ocean floor making it rough and rugged.
When thinking about this think about a pebble on the beach, what it is?
rounded due to erosion just as scientists thought the ocean floor would be.