A description of the hydrologic cycle

The hydrologic cycle is the term used to describe how water travels throughout the world system, from the surface to the atmosphere and back again. Over 95% of the planet's water resides in the earth's oceans and seas. The sun heats the oceans, causing water to evaporate into the atmosphere. Through the process of transpiration, plants also release water into the atmosphere. This water vapor travels throughout the atmosphere and eventually condenses into tiny droplets in clouds. If the conditions are right, the water in the cloud will fall as rain or snow. The water may be stored in lakes, rivers, or glaciers, absorbed by plants, ingested by animals, or soaked up by the ground. But most of the water will eventually travel back to the ocean, completing the water cycle.

Credit: Hailey King, NASA GSFC

For more info: http://earthobservatory.nasa.gov/Library/Water/water.html