Earth's energy cycle consists of all the energy inputs, outputs, and conversions within the Earth system, which must maintain an overall balance. A. Incoming short-wavelength solar radiation provides Earth with nearly all its energy and powers the hydrologic cycle as well as biological processes. B. Heat energy from Earth's interior, which powers the rock cycle, and the kinetic energy of Earth's rotation provide small additions to solar energy. C. Some of the incoming solar radiation is reflected, and the rest, after being absorbed, undergoes a series of conversions until it is reradiated into space as heat. D. Humans use only a small amount of the available solar energy for heat, satisfying most of their energy needs by burning coal, oil, and natural gas. E. Solar energy stored in rocks on Earth's surface is the primary source of geothermal energy and tidal energy. F. Earth's atmosphere and hydrosphere absorb most of the incoming solar radiation, using up much of the energy to power weather patterns, with only the remainder radiated out as heat.