Ocean Movements

Lesson Plan - Get It!

Audio:

The ocean moves three different ways.

These movements are called waves, tides, and currents.

• Do you know the difference between waves, tides, and currents?

Create the following chart on a piece of paper:

Think about what you know about the ocean. Use the chart to record what you think you know about waves, tides, and currents. Show your teacher or parent what you already know. As you progress with this lesson, you will add facts you learn about waves, tides, and currents to your chart.

If you have ever been to the beach, you have seen a wave. The scientific definition of a wave is, "the transfer of energy." Most ocean waves are created when wind moves across the surface of the water. As wind moves across the water, energy from the air molecules is transferred to the water. Ocean waves are considered mechanical waves because they travel through a medium, or a form of matter.

• What is the medium ocean waves travel through? Tell your teacher or parent.

If you said water, you are correct!

Waves can vary in size. Typically, waves you see at the beach can range from a few inches to a few feet high. Waves during a storm average ten feet high, but some events can create waves that are taller than buildings! Natural catastrophes, such as earthquakes and volcanos, can cause the ocean floor to shift. This movement on the ocean floor transfers energy to the water, causing it to move, too. The largest recorded wave was 500 meters high (that's more than 1,000 feet)! That wave occurred in Alaska as a tsunami. Tsunamis are rare, dangerous waves.

To learn more about tsunami waves, read Tsunamis (National Geographic Society).

• When you have visited the beach, have you ever noticed that sometimes the ocean water comes up higher on the beach than at other times of the day?

For example, if you sat your beach chair near the water in the morning, it might be partly underwater by later in the afternoon. This movement has to do with ocean tides. Tides are the rise and fall of sea levels caused by the gravitational pull of the moon. High tide is when the ocean level rises and comes up higher on the beach. Low tide is when the ocean level falls and moves out to sea. The ocean is constantly moving in a cycle of high and low tides based on the position of the moon. In most places, this cycle occurs one or two times per day.

• Did you know the ocean is constantly moving?

Even if it appears to be still, water below the surface is moving. Ocean currents are the continuous movement of seawater. Surface currents are mostly created by the wind. Deep water currents can be created by a number of factors, such as water temperature and salinity (the amount of salt in the water). Some currents — such as those created by storms — are temporary, and other currents are continuous.

Currents help influence global climates as they shift heat and energy around the world. Look at the image below. It shows continuous currents that exist throughout the world:

^{Image by Dr. Michael Pidwirny for the US government, via Wikimedia Commons, is in the public domain.}

• Which current is closest to where you live? Tell your teacher or parent.

Now, complete the chart you created at the start of this lesson as you read Currents, Waves, and Tides: The Ocean in Motion (Yasmine Abulhab, Smithsonian National Museum of Natural History).

When you finish reading the article, add any other facts you learned in this section to your chart. Share your chart with your teacher or parent.

Move on to the Got It? section to watch some videos about waves, tides, and currents.