Processes shape and maintain the physical environment. Therefore it is vital that students appreciate the complex relationships between processes and resultant features, and how these relationships give rise to patterns of spatial organizations. Five basic ideas help to explain the interactions and effects of physical processes. These are known as system, boundary, force, state of equilibrium, and threshold. Each system has boundaries, either real or arbitrary, within which it operates.
Systems exist in different states.
When a system is in equilibrium, driving forces such as gravity and resisting forces such as friction are in balance. After the avalanche a new state of equilibrium is established. It is essential that students understand the physical processes that act upon Earth and that such processes affect the choices made by people in different regions of the United States. Evaluating reports of world climate change requires knowing the factors that affect climate and weather in general and how the natural environment functions in particular regions. Climate and weather affect more than just personal decision-making on a daily basis.