This movement of warmer and cooler mantle rocks creates pockets of circulation within the mantle called

The answer is convection cells. Hope this helps ;). 

Answer: buoyancy forceexplanation: in simple terms, the principle states that the buoyancy force on an object is equal to the weight of the fluid displaced by the object, or the density of the fluid multiplied by the submerged volume times the gravitational acceleration, g. this is also known as upthrust.