1.   These form as a result of the continuing movement of lava below a surface crust.

2.   In the desert, for instance, the delicate surface crust of the soil is easily damaged by tire tracks, leaving whole strips of desert susceptible to erosion.

3.   The cow, tongue implanted in the surface crust of the ground, died where there was once a huge pond beneath large, hydroelectric transmission lines.

4.   The pan is preferable to broiling for achieving a good surface crust and moist interior.

5.   It keeps the soil from drying out excessively and they prevent soil from forming a surface crust.

6.   The earth is made up of the hard core, a liquid core surrounding it, and the surface crust.