thumb|300px|the water cycle thumb|earth's water cycle thumb|as the earth's surface water evaporates, winds move water in the air from the sea to the land, increasing the amount of fresh water on land. thumb|water vapor is converted to clouds that bring fresh water to land in the form of rain or snow. thumb|precipitation falls on the ground, but what happens to that water depends greatly on the geography of the land at any particular place. the water cycle, also called as the hydrologic cycle or the h2o cycle, describes the continuous movement of water on, above and below the surface of the earth. the mass of water on earth remains fairly constant over time but the partitioning of the water into the major reservoirs of ice, fresh water, saline water and atmospheric water is variable depending on a wide range of climatic variables. the water moves from one reservoir to another, such as from river to ocean, or from the ocean to the atmosphere, by the physical processes of evaporation, condensation, precipitation, infiltration, runoff, and subsurface flow. in so doing, the water goes through different phases: liquid, solid (ice), and gas (vapor). the water cycle involves the exchange of energy, which leads to temperature changes. for instance, when water evaporates, it takes up energy from its surroundings and cools the environment. when it condenses, it releases energy and warms the environment. these heat exchanges influence climate. the evaporative phase of the cycle purifies water which then replenishes the land with freshwater. the flow of liquid water and ice transports minerals across the globe. it is also involved in reshaping the geological features of the earth, through processes including erosion and sedimentation. the water cycle is also essential for the maintenance of most life and ecosystems on the planet. ==description== the sun, which drives the water cycle, heats water in oceans and seas. water evaporates as water vapour into the air. ice,rain and snow can sublimate directly into water vapour. evapotranspiration is water transpired from plants and evaporated from the soil. rising air currents take the vapour up into the atmosphere where cooler temperatures cause it to condense into clouds. air currents move water vapour around the globe, cloud particles collide, grow, and fall out of the upper atmospheric layers as precipitation. some precipitation falls as snow or hail, sleet, and can accumulate as ice caps and glaciers, which can store frozen water for thousands of years. most water f
Biogeochemical_cycle Forms_of_water Hydrology Soil_physics Water