Question: What is the basic idea involved in the concept of plasticity? Need Assignment Help? The ocean crust is not as solid as continental crust; large areas of it are plastic in nature. After major earthquakes large areas of the crust may be more plastic for hundreds of years. Over geologic time the Earth's crust is becoming more plastic and so can move more freely. Molten material may rise to the surface forming areas of plasticity. One layer of rock floats upon another so the crust is not as rigid as it may appear.