The water cycle describes the continuous movement of water on, above, and below the surface of the Earth. Water is evaporated from bodies of water by heat from the Sun, rises into the atmosphere as water vapor, cools and condenses to form clouds, and falls back to the Earth's surface as precipitation. The energy from the Sun and the force of gravity drive this cyclic movement of water between the atmosphere and the Earth's surface through the processes of evaporation, condensation, precipitation, infiltration, runoff, and subsurface flow. This cycle is essential for maintaining life on Earth.