1. Plasticity Plasticity is when a substance exhibits the characteristics of both a liquid and a solid. 

2. Plasticity: Lithospheric plates float on top of the asthenosphere.  The asthenosphere is a layer that demonstrates plasticty.  Heat and pressure cause a small amount of melting to occur in the asthenosphere. While still solid, the asthenosphere is able to flow.  It is a slowly flowing solid.

3. Plasticity When the material in the asthenosphere is heated (thermal heat from the deeper layers in the Earth), it becomes less dense and rises. While the cooler material (closest to the crust) is more dense tends to sink. Circulating currents carry the warmer material up and the cooler material down. These circular currents in the asthenosphere are called convection currents. The circulating convection currents cause the plates to move.