Why do tectonic plates move?

Tectonic plates, the massive segments of Earth’s crust, are in a state of constant, albeit slow, movement, varying between less than 2.5cm/year to over 15cm/year. This movement occurs due to the asthenosphere beneath them – a ductile layer accommodating the shifting of the solid, brittle plates above.

The theories explaining plate movement

The theories of plate movement are convection currents, ridge push and slab pull.

Convection Currents
This theory attributes the movement to convection currents within the mantle, driven by heat from Earth’s core, primarily from radioactive decay. The process involves heated rock in the mantle becomes less dense and rising. Reaching the crust, it spreads, dragging the plates along the surface.

Ridge Push
In this model, newly formed plates at oceanic ridges are warmer and elevated compared to colder, denser plates further away. The gravitational force causes the higher plates at the ridge to push outward, leading to plate separation.

Slab Pull
Slab pull is the most compelling theory to date. It suggests that the denser oceanic plate sinks into the mantle at destructive plate margins due to gravity, pulling the rest of the plate with it. Research indicates that slab pull is a primary driver for plate movement, with plates having more subducted edges moving faster. Ridge push also contributes but to a lesser extent.