- Waves and energy
- Wave erosion
- Wave deposition
- Protecting shorelines
- Explain how waves cause erosion of shorelines.
Describe features formed by wave deposition.
- Identify ways to protect shorelines from wave erosion.
barrier island: long, narrow island that forms parallel to shore when a sandbar builds up enough to rise above the water’s surface
breakwater: artificial barrier built in the water parallel to shore that reduces beach erosion by incoming waves
groin: artificial barrier built in the water perpendicular to shore to trap sand that is carried along the shore by longshore drift
longshore drift: movement of sediment along a shore by waves that strike the shore at an angle
sandbar: underwater ridge of sand running parallel to shore that is deposited by waves
sea arch: landform that results when waves create a hole in a wave-cut cliff
sea stack: landform that results when waves erode the top of a sea arch
spit: ridge of sand extending out from shore that is deposited by longshore drift
Introducing the Lesson
Show students a short video, such as one of those at the URLs below, of ocean waves crashing on rocks along a shore. Point out the loud sound of the surf and the foam and spray caused by the waves to help students realize how much energy they carry. Explain that waves like these can cause a lot of erosion. They can carve rocks into cliffs, arches, and other interesting shapes. Tell students they will learn about wave erosion and also wave deposition when they read this lesson.
Demonstrate features created by wave erosion and wave deposition by projecting dramatic images of sea cliffs, sea arches, sea stacks, barrier islands, and spits (see URLs below). Call on students to describe how each type of feature formed.
Have students do a think-pair-share activity to improve their understanding of basic lesson concepts. Ask students to think about the three questions listed below. Then pair English language learners with native English speakers and less proficient readers with more proficient readers. Ask partners to share and discuss their answers to the questions.
- How do waves cause erosion of shorelines?
- How can shorelines be protected from erosion?
- What features are formed by wave deposition?
Ask a few students to look at a map of the coastline nearest to their community and identify areas of erosion and deposition. Then have students predict how the coastline in these areas may change shape in the future. They should write a paragraph justifying their predictions.
Have students do the inquiry activity at the following URL (Station 6, “Wave Action”). In the activity, students will simulate waves and observe their effects on a sand “beach.”
A commonly held misconception about ocean waves is that they are generated by the water itself. Explain that most waves are generated by wind. As wind blows over the surface of water, its energy is transferred to the water. Another common misconception is that water moves toward shore with a wave. Explain that only energy moves through the water with a wave. Individual particles of water just move in little circles, and they do not move toward shore in the direction that the wave moves. Giving students experiences that challenge misconceptions is generally the most effective way to overcome the erroneous ideas. In the simple set of activities at the following URL, students can model generating waves with wind and model energy moving through water without the water moving along with the energy. The activities will help to allay the two misconceptions stated above.
Reinforce and Review
Copy and distribute the lesson worksheets in the CK-12 Earth Science for Middle School Workbook. Ask students to complete the worksheets alone or in pairs to reinforce lesson content.
Lesson Review Questions
Have students answer the Review Questions listed at the end of the lesson in the FlexBook® student edition.
Check students’ mastery of the lesson with Lesson 10.2 Quiz in CK-12 Earth Science for Middle School Quizzes and Tests.
Points to Consider
Moving air, like moving water, causes erosion. Moving air is called wind. How does wind cause erosion? Does the wind carry particles in the same ways that moving water does?
What landforms are deposited by wind?