Wind, tacuinum sanitatis casanatensis (14th century) Wind is the flow of air or other gases that compose an atmosphere (including, but not limited to, the Earth's).[1] It occurs as air is heated by the Sun and thus rises. Cool air then rushes to occupy the area from which the hot air has just moved. It can be loosely classified as a convection current.[citation needed] Winds are commonly classified by their spatial scale, their speed, the types of forces that cause them, the geographic regions in which they occur, and their effect. While wind is often a standalone weather phenomenon, it can also occur as part of a storm system, most notably in a cyclone. Winds can shape landforms, via a variety of aeolian processes. In human civilization, wind has inspired mythology, changed the course of history, expanded the range of transport and warfare, and provided a power source for mechanical work, electricity, and recreation.