Chapter 6.1, Problem 1BYL

To determine

The way by which thermal vibrations and pressure affect a crystalline structure.

Answer to Problem 1BYL

When temperature increases, vibration also increases and it results in the breaking of bonds and thereby melting of rocks or minerals. The increase in pressure causes the compression of solid and makes it more resistant to melting.

Explanation of Solution

Atoms and bonds are always vibrating in solids. An increase in the temperature results in an increase in vibration. As a result, it will reach the point that involves the eventual breaking of bonds and the melting of rocks. An increase in pressure has opposite effect. The increasing pressure compresses the solid and makes it more resistant to melting.

When the pressure and bond strength are sufficient to overcome vibrations due to temperature, a mineral or rock will remain as solid. The increase in pressure occurs below the surface of the Earth mainly due to the weight of the overlying rocks. It gradually increases with the depth of burial.

When pressure and bond strength are insufficient to hold a solid material together, it results in the melting of rock or mineral. Different types bonds break at different temperatures. Therefore, magma generally comprises of molecules and materials that are partially bonded or weakly bonded within the melt.