- There are three generally accepted theories to account for the motion of the plates.
- Most are based upon temperature-induced density differences (TIDD) causing movement of mantle materials.
Mantle convection current theory
- First proposed by Arthur Holmes in 1928.
- As the warm mantle rises then spreads across the Earth's surface, it drags along the lithosphere plates.
- The cooled mantle then descends.
- Some scientists hold that the convection loops are large, using the entire mantle.
- Others suggest a smaller asthenosphere feature.
- Depends upon the mound formed at the mid-ocean ridge material by the warm, less-dense oceanic crust.
- As this crust cools and moves away from the ridge,
- it contracts and begins to sink into the mantle.
- This pulls the plate along.
- An alternative way to view this is as slab-push.
- The elevated ridge pushes the plate along.
Hot Spot theory
- The long, thin plumes of hot spots are a possible convection current based engine for plate motion.