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The seasons are a well-known example of a cycle.
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What is a Cycle?

You've probably heard of the water cycle, the solar cycle, the rock cycle and maybe even the carbon, nitrogen and phosphorus cycles.

Very simply, when scientists talk about cycles, they are talking about sequences of events that repeat themselves. Some cycles are very simple. For example, the phases of the Moon represent a cycle in that they always repeat – New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, Waning Crescent and then back to New Moon!

In Earth system science, cycles can be very complex. There are many different types of elements and nutrients in the Earth system. These elements can not be made or destroyed, but they can change their location. Locations where elements can be stored are called reservoirs. Elements can move in and out of a reservoir over time. In this way, elements cycle through the Earth system. These cycles are called biogeochemical cycles.

Last modified June 29, 2005 by Jennifer Bergman.

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The Summer 2010 issue of The Earth Scientist, available in our online store, includes articles on rivers and snow, classroom planetariums, satellites and oceanography, hands-on astronomy, and global warming.

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