The water cycle (also called the hydrological cycle) describes how water continuously moves through the environment.

Four Main Stages

1. Evaporation

   The sun heats surface water in oceans, lakes, and rivers, turning liquid water into water vapor that rises into the atmosphere.

2. Condensation

   As water vapor rises and cools, it turns back into tiny liquid droplets that form clouds and fog.

3. Precipitation

   Water falls from clouds back to the ground as rain, snow, sleet, or hail depending on temperature.

4. Collection

   Water collects in oceans, lakes, rivers, and groundwater. Some soaks into the soil (infiltration), and the cycle begins again.

Additional Processes

• Transpiration — plants release water vapor through their leaves
• Runoff — water flows across the land surface into streams and rivers
• Sublimation — ice turns directly into water vapor without becoming liquid first

The water cycle is powered by energy from the sun and pulled by gravity. It is a closed system — the total amount of water on Earth stays the same.