The range of Earth’s surface temperatures and atmospheric pressures permits water to occur naturally as a solid, liquid, and vapor. Water is present in all Earth’s climate subsystems. In broadest terms, the hydrosphere includes liquid water at the Earth’s surface, water in the atmosphere in all its forms, and water in the cryosphere stored as ice. It extends several kilometers below Earth’s surface and reaches 12 kilometers into the atmosphere.

Salem Press Encyclopedia of Science, 2023. 3p.