The seasons are a well-known example of a cycle. Click on image for full size (86) Windows Original

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.

The seasons are a well-known example of a cycle. Click on image for full size (86) Windows Original

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 seasons of the year represent a cycle in that they always repeat – Winter, Spring, Summer, Fall, and then back to Winter!

The nitrogen and carbon cycles are very complex cycles. They fit into the category called biogeochemical cycles.

The seasons are a well-known example of a cycle. Click on image for full size (86) Windows Original

Cycles are events that repeat. Some cycles are very simple and other cycles are very complicated. One example of a cycle is the days of the week -- Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday, and then back to Monday! Can you think of any other cycles? How about the seasons? Summer, Fall, Winter and then Spring…over and over and over it goes!

Earth scientists study cycles a lot. One of the cycles they study is the water cycle. Other complicated cycles are called biogeochemical cycles.