Plate Tectonics

Measuring Plate Motion

• Date the islands created by hot spots
• Date the magnetic stripes on the floor of the ocean
• Use of global positioning system (GPS)
• Very Long Baseline Interferometry (VLBI)

Mechanism of Plate tectonics

No proposed mechanism for plate tectonics accounts for all of the interactions between the plates. Researchers do agree on some of the basics.

• Convection currents in the mantle are the basic driving force for plate movement where oceanic plates act as the cold downward moving part of the convection cycle.
• Mantle convection and plate tectonics are part of the same system.
• The movements of the plates and mantle are unequal because of the unequal distribution of heat.

Processes that contribute to plate motion includes the slab-pull mechanism, the ridge-push mechanism and mantle plumes.

• Slab-pull Mechanism - cool and dense oceanic crust sinks into the asthenosphere and pulls the remaining lithosphere.
• Ridge-push Mechanism - the elevated oceanic ridge system causes oceanic lithosphere to slide down the flanks of the ridge.
• Mantle Plumes - hot, bouyant plumes of hot material.