Topic Overview: Overview

What is a system? What do you know about the Earth system? To find out, try playing the online activity Earth System Cards. Or try one of the other great activities on the Earth system. You might have questions. Don't worry. We gathered some facts about the Earth system.

Many people who study Earth think of it as a system. A system is a group of parts that work together as a whole. For example, your body is a system. It is a group of parts called organs. Organs such as your heart, lungs, and brain work together to keep you alive.

The scientists who think of Earth as a system are called Earth system scientists. These scientists divide Earth into four major parts called spheres. Earth's four spheres are land, water, living things, and air. Each thing in the Earth system belongs to one of these four spheres.

Earth's spheres are often connected by cycles. Cycles are patterns that repeat. For example, the change of seasons is a cycle. Many parts of the world have four seasons in this cycle. In these places spring changes to summer. Summer changes to fall. Fall changes to winter. Winter changes to spring. This cycle takes one year to complete. It repeats every year.

Like many other cycles, changing seasons link Earth's spheres together. During the cycle of seasons, the air temperature changes. Air is warmer in the spring and summer. It is cooler in the fall and winter. The air temperature affects the type of water that falls from the sky. When the air is warm, water falls from the sky as rain. When the air is cold, water falls from the sky as snow. The temperature of the air and the type of water that falls from the sky affect the living things in an area. For example, some animals that live in cold and snowy places grow thick fur. The fur keeps them warm. Some animals move to warmer places when it gets cold and snowy. They move back home in the spring. And some animals just sleep all winter in their warm homes. These are ways the cycle of seasons connects Earth's air, water, and living things.