Tectonic plates move primarily due to forces generated by processes in Earth's mantle and gravity acting on the plates themselves. The main causes include:
- Mantle Convection Currents: Heat from Earth's interior, largely from radioactive decay, causes hot, less dense mantle rock to rise and cooler, denser rock to sink, creating convection currents. These currents in the ductile asthenosphere can drag the rigid tectonic plates above, moving them slowly over time
- Slab Pull: This is considered the most significant force driving plate motion. Older, colder, and denser oceanic plates sink into the mantle at subduction zones due to gravity, pulling the rest of the plate along with them
- Ridge Push: At mid-ocean ridges, newly formed oceanic crust is warmer and elevated compared to older, cooler crust. Gravity causes this higher ridge to push the plate away from the ridge, contributing to plate movement
- Trench Suction: Small convection currents near subduction zones can also pull plates downward and help drive their motion
Overall, gravity is the fundamental force enabling these mechanisms, with slab pull being the dominant driver of plate tectonics, assisted by mantle convection and ridge push
. In summary, tectonic plates move because of mantle convection currents that circulate heat within Earth, combined with gravitational forces acting on dense, sinking plates at subduction zones (slab pull), and pushing forces at mid-ocean ridges (ridge push)
