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Earth's water is always in movement, and the natural water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the Earth. Water is always changing states between liquid, vapor, and ice, with these processes happening in the blink of an eye and over millions of years.
Note: This section of the Water Science School discusses the Earth's "natural" water cycle without human interference.
• Water Science School HOME • The Water Cycle •
What is the water cycle? I can easily answer that—it's me, Drippy, all over!
The natural water cycle describes the existence and movement of water on, in, and above the Earth. Earth's water is always in movement and is always changing states, from liquid to vapor to ice and back again.
The water cycle has been working for billions of years and all life on Earth depends on it continuing to work; the Earth would be a pretty stale place without it.
Note: Our information only covers the natural water cycle, which does not take human activities into account. In today's world, humans have a major impact on many components of the water cycle.
Below are other science topics associated with the water cycle.
The USGS Water Science School offers many resources to teachers help teach students all about water.
Below are multimedia items associated with the water cycle.