The surface of the rock expands very slightly,but the inside of the rock,which is not heated,does not expand. This causes a little crack,and gradually little pieces of the rock break away.

• 岩石的表面膨胀很小，但是没有被加热的岩石的内部却不膨胀，这使得岩石产生细小裂缝，一片片小石头片将渐渐地剥蚀下来。