Plate Tectonics Forces
Ridge push, slab pull, and basal drag — the engines of plate motion
Plate velocity: 3.2 cm/yr
Slab pull is the dominant driving force — cold, dense oceanic lithosphere sinking at subduction zones pulls the plate like a falling chain. Ridge push arises from gravitational sliding off the elevated mid-ocean ridge. Basal drag can either drive or resist motion depending on mantle flow direction. Plates with large attached slabs (Pacific, Nazca) move ~3–10 cm/yr; plates without slabs (Africa, Antarctica) move <2 cm/yr.