- The earth is a system that consists of several sub-systems such as geosphere, hydrosphere, atmosphere and biosphere.
- There are close relationships of transformation of matter and energy among the systems.
- The transformation of matter is cyclic within each sub-system and within the earth as a whole system.
- The transformation among and within the earth systems involves the transition between reservoirs and between one form to another. For example, within the geosphere there are cyclic sequences of processes such as lithification, uplift, weathering, transformation, sedimentation, burial, lithification that form a long-term cycle of rocks.