What Is a Wave?Most waves form when winds blowing across

the water’s surface transmit their energy to the water.

- Wave Action

Water Motion Activity

Click the Active Art button to open a browser window and access Active Art

about water motion.

- Wave Action

How Waves Change Near ShoreNear shore, wave height increases and

wavelength decreases.

- Wave Action

How Waves Change Near ShoreA tsunami is usually caused by an earthquake

beneath the ocean floor.

- Wave Action

How Waves Affect the Shore As waves come into shore, water washes up the beach at an angle,

carrying sand grains. The water and sand then run straight back down the beach.

- Wave Action

What You Know

What You Learned

Using Prior KnowledgeBefore you read, look at the section headings

and visuals to see what this section is about. Then write what you know about waves in a graphic organizer like the one below. As you read, write what you learn.

1. There are waves in the ocean.2. Wind causes waves.

1. Waves move energy to the shore.2. Earthquakes cause tsunamis.

- Wave Action

Wave Characteristics

Click the Video button to watch a movie about

wave characteristics.

- Wave Action

End of Section:Wave Action

What Causes Tides?Tides are caused by the interaction of Earth,

the moon, and the sun.

- Tides

What Causes Tides?Spring tides and neap

tides are caused by the positions of Earth, the sun, and the moon.

- Tides

Plotting TidesThis table lists the

highest high tides and the lowest low tides for one week at the mouth of the Savannah River, where it meets the Atlantic Ocean in Georgia.

- Tides

Plotting TidesGraphing:

Use the data in the table to make a graph. On the horizontal axis, mark the days. On the vertical axis, mark tide heights ranging from 3.0 to –1.0 meters. (Hint: Mark the negative numbers below the horizontal axis.)

Check students’ progress as they make their graphs. The number –1 should occur at the base of the y-axis.

- Tides

Plotting TidesGraphing:

Plot the tide heights for each day on the graph. Connect the high-tide points with one line and the low-tide points with another line.

Make certain that students connect the correct points with lines.

- Tides

Plotting TidesInterpreting Data:

How do the high and low tides change during the week?

During the first six days, the high-tide value increases steadily while the low-tide value decreases. On day 7, the trends reverse.

- Tides

Plotting TidesInferring:

What type of tide might be occurring on day 6? Explain.

Spring tide might be occurring on day 6, when there is the greatest difference between high and low tides.

- Tides

Previewing VisualsBefore you read, preview Figure 11. Then

write two questions you have about the diagram in a graphic organizer like the one below. As you read, answer your questions.

Q. When do spring tides occur?

A. During the full and new moon phases

Q. What is a neap tide?

A. A smaller tide that happens at the first- and third-quarter moons

Spring and Neap Tides

- Tides

More on Tides

Click the PHSchool.com button for an activity about tides.

- Tides