Final answer:
The convection necessary for plate motion occurs in the Earth's mantle, where warmer material rises and cooler material sinks, driving the movement of tectonic plates.
Step-by-step explanation:
The convection necessary for plate motion occurs in the mantle of the Earth. This process is vital as it drives the movement of the tectonic plates by the flow of heat escaping from the interior to the exterior, causing warmer material to rise and cooler material to sink. This is referred to as mantle convection, which is the primary force behind the movement of plates in the Earth's crust and can lead to phenomena like the creation of new crust at mid-ocean ridges or the destruction of crust in subduction zones.
The Earth's mantle surrounds the core and consists of solid rock that can deform and flow, reacting to the temperature differences within. Considering the structure of the Earth, which includes the crust, mantle, outer core, and inner core, it is the mantle where this slow but continuous movement occurs, functioning like a giant conveyor belt partly powered by the heat coming from the core region.