The process by which the more dense plate is forced down below a less dense plate is called what?

• A. Subduction
• B. Convection
• C. Seafloor Spreading
• D. Lithosphere

Answer: (A)

Subduction is the process where the more dense plate is forced down beneath the less dense plate at a convergent boundary, sinking into the mantle under gravity. This density contrast makes the cooler, thicker, oceanic or older lithosphere plunge beneath its lighter neighbor, often continental crust. As the slab sinks, it pulls the rest of the plate downward and can melt as it descends, feeding volcanic activity and creating deep trenches and strong earthquakes along the boundary. This is different from convection, which is the broader movement of mantle material powering plate motion; seafloor spreading, which builds new ocean floor at divergent boundaries as plates pull apart; and lithosphere, which is the rigid outer shell of the Earth rather than a process.