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.