GEOLOGY

Detailed explanation-1: -A cyclical motion occurs because of density differences in the mantle. Heated, less dense lower regions of the fluid mantle rise, and denser, cooler regions sink due to gravity. The combined motions serve as the engine for crustal plate movement. The theory that continents were once connected but have drifted apart.

Detailed explanation-2: -The deep Earth is very hot, while its surface is quite cool. This causes hot material within the Earth to rise, until it reaches the surface where it moves sideways, cools, then sinks. This circular motion is called convection. Convection within the mantle drives the motion of the overlying plates.

Detailed explanation-3: -Convection currents are powered by the heat deep within the earth. As material heats up, it becomes less dense and rises near mid-ocean ridges. As the heated material moves farther from the heat source, it cools, becomes more dense, and begins to sink. This cycle of heating and cooling is called a convection current.

Detailed explanation-4: -Convection currents drive the movement of Earth’s rigid tectonic plates in the planet’s fluid molten mantle. In places where convection currents rise up towards the crust’s surface, tectonic plates move away from each other in a process known as seafloor spreading (Fig. 7.21).

Detailed explanation-5: -Just like the water, the magma creates movement of a circular motion called convection currents. In conclusion the plates move across the earth because of convection currents beneath the crust.