An Introduction to Earth System Science

An Introduction to Earth System Science
A system is a group of parts that works together. 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.

Earth is also a system. It is a group of four major parts called "spheres." Earth's four spheres are land, water, living things, and air. Each thing in the Earth system belongs in one of these spheres.

Happenings that occur in Earth's spheres are called events. Events that repeat themselves are called "cycles." Some cycles involve more than one sphere. This is how the parts of the Earth system work together.

An example of an event in which cycles within the Earth’s spheres are affected is the wildland fires that occurred in Yellowstone National Park ten years ago. Almost all the forest fires were caused by a combination of three things:

a very dry, windy summer that drew moisture out of the living grasses and trees,
thunderstorms that produced a great amount of lighting but very little rain,
a lot of dead branches and pine needles were on the ground and ready to burn.

How might this event—the Yellowstone fires—have affected the water, the air, the land, and the living things in and around the park?

Effects on Water
Burning pine needles and wood and other plant material can produce an ash that may come down in nearby streams.

Effects on Air
A big forest fire will affect the air and the weather patterns in the area. Warm air rises, so forest fires create updrafts of air. The heat from the fires also tends to cause any moisture in the air or moisture that is still in the plants to evaporate.
Effects on Land
When we say land, we usually mean the rocks that make up our planet. Besides scorching the surface of the rocks, these fires did very little damage to the land. However, the fires did affect the topsoil. The top layer of soil provides nutrients plants need to grow. It also provides something for their roots to hold on to. When land is burned, this topsoil is often lost.
Effects on Living Things
Animals that could escape the fast moving fires usually did unless they got trapped. After the fire is extinguished, animals that graze on the grasses might have a problem finding food.

Fish in some streams that received a lot of ash fall didn't do very well. They choked on the ash in the water as it got into their gills.

Many plants were destroyed but their seeds survived below the level of the burned topsoil. Some pine cones even need a fire to open them and release their seeds.

Using the Earth System Diagram below will help you to see how an event such as the Yellowstone fires affects each of Earth’s four spheres. Notice that the event is in the center and that arrows run from the event to each of the four spheres. These arrows represent the effects the event can have on the spheres.

You can write notes to yourself about the effects the event has had on the spheres as is shown on the diagram.

Changes that occur in one of the spheres can affect the event. For example, a forest fire draws out the moisture from plants ahead of it. It's almost like the forest fire is preparing the next space to burn. This means that when there is a change in one of the spheres, it can have an effect on how the "event" continues, too.

The diagram below reflects how the spheres affect the event.

If the event can affect the spheres and the spheres can affect the event, do you think it’s possible that the spheres can affect one another? Why, of course! For example, the burning updrafts of the fire put ash into the air. The ash is blown by the wind. It also makes little centers for raindrops to form around if there is moisture in the air. Or consider this—might the smoke in the air from the fires affect the breathing animals and people hundreds of miles from the fire?

Take a look at the third diagram. It has arrows running to and from each of the spheres. These arrows represent how what happens in one sphere can affect something that happens in another sphere. These two-way cause-and-effect relationships are called interactions.

Only a few of the many possible interactions have been listed above for the forest fires event. These interactions are simply a sketch of some reasonable impacts and results. There are many other possibilities.

The process of looking at the various types of interactions that can occur on the Earth System Diagram is called an Earth system science (ESS) analysis. Looking at the diagram will help you to sketch out the possible impacts of any event on Earth's spheres. In addition to events that make the newspaper or TV news, you can use an ESS analysis to look at an event near your hometown or even to consider the potential impacts of a proposed event or action.

Conducting Earth System Science in Your Classroom
Ask your students to think about the relationships among the spheres. Be sure you ask them to explain impacts or connections between and among spheres and events. When you ask your students about impacts and connections, you need to emphasize that they are looking for possible impacts, not necessarily ones that have already been proven in the field. In addition, they are not trying to list every possible interaction from an event. Frequently, an impact may not be obvious to you, but when a young person explains why he or she has made the suggestion, it may be quite sensible. Use your own judgment and read your learners’ interest and enthusiasm.

[ Back to Week 2 ]

HTML by Chris Kreger
Maintained by ESSC Team
Last updated August 04, 2000