Chapter 9. The Earth's Energy Sources

9.1 Introduction

The goals of this module: At the end, you should be able to:

1. Identify three of the five sources of energy that drive motion and change in the Earth.
2. Explain how solar energy and the rotation of the Earth work together to create the motions of the Earth's atmosphere.
3. Explain how solar energy drives ocean currents.

In this module you will explore:

1. Three of the five energy sources for changes in the Earth: solar energy, Earth's rotation, and tidal forces. (The other two are heat of formation and radioactive decay.)
2. Ways that this energy works to create motion and change in the Earth's atmosphere and oceans.

Why you are doing it: By understanding the Earth's energy sources and how this energy is transferred, you can better understand the processes that cause motions and changes in the Earth.

9.2 Background

The Earth as seen from the Moon

The Earth is our home planet. Nearly all of the events of human history, all the vast changes that we have experienced, have taken place here on the surface of the Earth. But the Earth itself is constantly changing too. Earth is a complex system that includes land, water, and air, and all of these parts interact with each other to create motion and change. All these motions and changes require energy to continue.

Different energy sources act on different parts of the Earth. In this activity, you'll explore how different energy sources drive different motions.

Let's start with the atmosphere.

9.3 Solar Energy Heats the Atmosphere

In the animation below, on the right, you see a pot of water heating on a stove. Turn on the stove and watch what happens!
You have probably seen something like it yourself. The circular motion of the water in a heating pot is called convection. It turns out that the motion of air in the Earth's atmosphere can also be explained by convection.

On the left, you see the Earth's surface and its atmosphere. "Light" the sun and watch what happens!

9.4 Earth's Rotation Affects the Motion of the Atmosphere

The animation below is a more realistic diagram of the Earth, with the Earth's rotation included. Click the Sun to heat up this Earth, and watch what happens.

Question Sequence

Question 3.

How are the motions of air on the real Earth similar to air motions on the imaginary non-rotating Earth? In the real, rotating Earth air

A.

follows the pattern of rising at the equator.

B.

spreads toward the poles.

C.

sinks again after traveling some distance.

D.

forms cells that include both up-and-down and lateral motion.

E.

All of the above.

3

Try again. This is a correct answer, but not the only one!

Correct. But Earth's rotation causes the air to spread out in the direction of rotation too.

Incorrect. But Earth's rotation causes the air to spread out in the direction of rotation too.

Question 4.

In the 16th century, Spanish sailors realized that they could sail quickly from Spain to its Central American colonies. This is because the winds were pushing them in the direction they wanted to go. True or False?

A.

True

B.

False

3

Take another looks at the animation and note that Central America is southwest of Spain. Try again!

Correct. The movement of air in the atmosphere results in winds. The animation above and to the right shows air moving along the Earth's surface from the northeast to the southwest - so the winds along the surface blow from northeast to southwest. When the sailors sailed from Spain to its colonies, they traveled southwest, so these winds were at their back. Traveling with the winds at their back, they could move more quickly.

Incorrect. The movement of air in the atmosphere results in winds. The animation above and to the right shows air moving along the Earth's surface from the northeast to the southwest - so the winds along the surface blow from northeast to southwest. When the sailors sailed from Spain to its colonies, they traveled southwest, so these winds were at their back. Traveling with the winds at their back, they could move more quickly.

9.5 Solar Energy Moves the Oceans

The atmosphere is not the only thing in constant motion on Earth - the oceans move too. The energy that drives this motion also comes from the Sun. Study the animation below to see how the oceans move.

9.6 Review Activity

Now, review your knowledge. Look at the following diagram, which shows different types of motion on the Earth. Label the diagram with the energy sources that drive each type of motion by dragging and dropping the provided labels. Some motions will require two labels, some only one. You will use some of the labels more than once.

9.7 Quick Check Quiz

Indepth Activity: The Earth's Energy Sources

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