17.4 Cause of Plate Motions

Mantle Earth’s interior between the crust and the core Large-scale motion is believed to be the mechanism that drives the movement of tectonic plates

Convection Transfer of thermal energy by the movement of heated material from one place to another Ex. Boiling water Heat comes from radioactivity within the mantle

Convection Currents Cycle of warm water rising and cool water sinking The cooling of matter causes it to contract slightly and increase in density then it sinks due to gravity Warmed matter is then displaced and forced to rise

Convection Currents Develop in the mantle Move the crust and outermost part of the mantle Transfer thermal energy from Earth’s interior to its exterior

Rising material spreads out, lifts and splits lithosphere at divergent boundaries Downward movement pulls convergent boundaries

Ridge push Tectonic process associated with convection currents Occurs when the weight of an elevated ridge pushes an oceanic plate toward a subduction zone

Slab pull Tectonic process associated with convection currents in Earth’s mantle Occurs as the weight of the subducting plate pulls the trailing lithosphere into a subduction zone.

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