Final answer:
Subduction and sea-floor spreading have significant impacts on the ocean floor, including the formation of ocean trenches and the creation of new crust at rift zones. These processes shape the ocean floor and are important for plate tectonics.
Step-by-step explanation:
Subduction and sea-floor spreading have significant impacts on the ocean floor. Subduction occurs when one tectonic plate is forced beneath another, typically leading to the formation of ocean trenches. The subducted plate is pushed into regions of high temperature and pressure, eventually melting and recycling its material into a downward-flowing convection current. Sea-floor spreading, on the other hand, is the process of new crust being added to the Earth's surface at rift zones. This process creates basaltic lava, which fills the space between the diverging plates and forms most of the ocean basins. Overall, subduction and sea-floor spreading play crucial roles in shaping the ocean floor and contributing to the dynamic nature of plate tectonics.