FOR PERSONAL USE. Shoreline Erosion BROWARD COUNTY ELEMENTARY SCIENCE BENCHMARK PLAN ACTIVITY ASSESSMENT OPPORTUNITIES. Grade 4 Quarter 1 Activity 9

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1 activity 9 Shoreline Erosion BROWARD COUNTY ELEMENTARY SCIENCE BENCHMARK PLAN Grade 4 Quarter 1 Activity 9 SC.D The student knows that the surface of the Earth is in a continuous state of change as waves, weather, and shifts of the land constantly change and produce many new features. SC.D The student knows that some changes in the Earth s surface are due to slow processes and some changes are due to rapid processes. SC.H The student knows that a successful method to explore the natural world is to observe and record, and then analyze and communicate the results. SC.H The student knows that to work collaboratively, all team members should be free to reach, explain, and justify their own individual conclusions. SC.H The student knows that to compare and contrast observations and results is an essential skill in science. SC.H The student knows that a model of something is different from the real thing, but can be used to learn something about the real thing. SC.H The student knows that through the use of science processes and knowledge, people can solve problems, make decisions, and form new ideas. ACTIVITY ASSESSMENT OPPORTUNITIES The following suggestions are intended to help identify major concepts covered in the activity that may need extra reinforcement. The goal is to provide opportunities to assess student progress without creating the need for a separate, formal assessment session (or activity) for each of the 40 hands-on activities at this grade level. 1. Ask, Do tides affect erosion in rivers or streams? (Very slightly because there is less water to move; but, where rivers flow into an ocean, tides may have a small but noticeable effect.) What happens to shoreline erosion during the storm surge of a hurricane? Why? (Erosion is greatly increased due to more water moving, higher waves, more wind making waves both higher and moving them faster, the water moving farther inland, and so on.) broward county hands-on science Quarter 1 99

2 2. Use the Activity Sheet(s) to assess student understanding of the major concepts in the activity. In addition to the above assessment suggestions, the questions in bold and tasks that students perform throughout the activity provide opportunities to identify areas that may require additional review before proceeding further with the activity. 100 activity 9 Shoreline Erosion

3 activity 9 Shoreline Erosion OBJECTIVES Students investigate the erosion that occurs along a shoreline as a result of tidal and wave action. The students simulate the erosive effect of wave action in their stream tables compare the erosion caused by large and small waves predict and then observe the effects of a breakwater on shoreline erosion SCHEDULE About 30 minutes VOCABULARY breakwater tidal action wave MATERIALS For each student 1 Activity Sheet 9 1 pair safety goggles* For each team of four 1 container, 1-L 1 bag sand (from Activity 6) 1 stream table (from Activity 7) 1 tray, plastic For the class 1 roll aluminum foil 1 bag, plastic, resealable 1 block clay, modeling 1 pkg nylon mesh pebbles, assorted sizes* photographs of breakwaters (optional)* 1 pair scissors* 24 sticks, wooden water, tap* DSR Erosion *provided by the teacher PREPARATION Make a copy of Activity Sheet 9 for each student. At some point before the activity, you will need to go outdoors and collect several cups of assorted-sized pebbles for students to use in their breakwaters. Place the following items at a distribution station: a roll of aluminum foil, pebbles of assorted sizes, a package of nylon mesh, a pair of scissors, a block of modeling clay, and twenty-four wooden sticks (tongue depressors) Each team of four will need their stream table from Activity 7, a 1-L container filled with tap water, the sand they set out to dry on newspaper after Activity 6, a piece of modeling clay (to fill the hole in the stream table), a plastic tray, and access to the items at the distribution station. BACKGROUND INFORMATION About three-fourths of Earth s surface is covered by water, most of which is in the oceans. If this water were motionless, it would contain little force and have virtually broward county hands-on science Quarter 1 101

4 no effect on the shoreline. However, the water in oceans (and in very large lakes) is constantly in motion in the form of tidal action and waves. As the moon orbits our planet, it exerts a gravitational pull on the surface of the Earth. Although this pull is exerted on both land masses and oceans, only the water in the oceans is dramatically affected. The moon s gravitational pull causes the water to form a single mound of water that travels around the Earth, causing a periodic change in the surface level of the oceans. This phenomenon is called the tide. The energy in this tidal action is great, but because its speed is relatively slow and distributed over large expanses of water, it causes little erosion. However, as tides encounter the shoreline at areas with narrow inlets, such as rivers or streams, some of the water is forced upriver, changing the direction of the current so that it flows inland. This reversal of current causes erosion along the banks of the river. More important when considering shoreline erosion is the effect of the wind-driven waves. As storms travel across the ocean, the wind they generate sweeps across the water s surface. Some of the wind s energy is absorbed by the water, causing waves to form. Much of a wave s energy is below the surface of the water. As the wave rapidly approaches the shoreline, the energy is forced upward by the increasingly shallow depth of the water. The waves become steeper and then break on the beach. Breakwaters are artificial barriers constructed along the shoreline to absorb or deflect the energy of the breaking waves, thereby reducing the amount of erosion. In this activity, the students use their stream tables to observe shoreline erosion caused by waves. They then use materials to construct breakwaters and predict and observe their effectiveness. 102 activity 9 Shoreline Erosion Activity Sheet 9 Shoreline Erosion 1. How much sand was eroded by the small waves? (Use the grid for clues.) All of the sand that the small waves touched moved and eroded a little bit. 2. How much sand was eroded by the large waves? more than by small waves 3. Which size waves caused more erosion? The larger waves caused more erosion. 4. Draw your breakwater design below. Designs will vary. 5. Predict how effective your breakwater will be. Predictions will vary. 6. Record your observations of your breakwater s effectiveness. Observations will vary.

5 1 Guiding the Activity Ask, What are some of the factors that cause erosion along a shoreline? Write the word wave on the board. Ask, How do waves get their energy? Additional Information The constant force of waves breaking on the shoreline. Energy from the wind blowing across the surface of the water is absorbed by the water and forms waves. As a wave nears the shore, the increasingly shallow depth of the ocean floor forces the energy of the wave upward, steepening the wave until it breaks. 2 Ask, What are some factors that affect the size and strength of waves? Write the term tidal action on the board. If necessary, explain that tidal action is the regular rise and fall of the surface level of the oceans. Tell students that the gravitational pull of the moon is responsible for causing the tides. Explain to students that in this activity they will construct a shoreline in their stream tables to observe the erosion caused by waves. Distribute a copy of Activity Sheet 9 to each student. Each team of four will need their stream table from Activity 7, the approximately 6 lb of sand that they set out to dry after Activity 6, a 1-L container filled with tap water, a plastic tray, and a small wad of clay. Have each team plug the hole (in the grommet) in their stream table with a piece of clay and then add the sand to the other end of the stream table. Instruct the students to use their hands to smooth and gently slope the sand so that it covers two-thirds of the stream table. The speed and direction of the wind, whether it is high or low tide when the waves reach shore, how long the wind blows, and the distance of open water the wind blows across. Explain that although the majority of shoreline erosion is a result of the waves breaking on the beach, tidal action causes the breaking point of the waves along the shoreline to change, thereby increasing the total area of the shoreline subject to wave pounding. 3 Note: Unlike in previous experiments, the stream tables will not be elevated at one end during this experiment. broward county hands-on science Quarter 1 103

6 Guiding the Activity Additional Information 4 Instruct the students to pour water from the 1-L container into the empty end of their stream tables so that the water reaches the sand. Have the students dip one end of the plastic tray into the water in their stream table and move it slightly back and forth to create small waves (see Figure 9-1). 5 6 Have them record their observations on Activity Sheet 9 and then smooth the sand back to its original condition. Figure 9-1. Making waves. Have them repeat the wave action, this time increasing the size of the waves. Have them answer questions 2 and 3 on the activity sheet. Ask, How did the erosion caused by large waves differ from that caused by small waves? Ask, What can we do to reduce the amount of shoreline erosion caused by waves? 104 activity 9 Shoreline Erosion sand stream table Students should use the grid in the bottom of their stream table for clues as to how much sand has eroded. water tray The waves should not be so large that they overflow the stream table. Large waves have more volume and more force than small waves and therefore caused more erosion.

7 7 8 Guiding the Activity Write the word breakwater on the board and distribute the photographs of different types of breakwaters. Explain that breakwaters are artificial barriers positioned offshore to deflect or reduce the energy of the waves as they approach the shoreline. In doing so, they limit shoreline erosion. Turn the students attention to the materials that are available at the distribution station: modeling clay, pebbles, wooden sticks, aluminum foil, and nylon mesh. Tell them that they are to design a breakwater and that any of these materials can be used in their design. Have them predict the effectiveness of their breakwaters and record their predictions on Activity Sheet 9. Once they have finished designing their breakwaters and recording their predictions, have the students build them, perform the wave action experiment again, and record their observations. After everyone has finished experimenting and recording, ask, How effective were your designs? Have the students with the most effective breakwaters draw their designs on the board and explain why they were so successful. Ask, What are some of the drawbacks of the materials used in your breakwater construction? Ask, From what you have observed, is there any way to completely stop shoreline erosion caused by waves? As appropriate, read or review page 10 from the Delta Science Reader Erosion. Additional Information The modeling clay can be used to attach breakwater materials to one another and to the stream table. Tell students to draw their breakwaters on their activity sheets. Remind students to use the grid in the bottom of their stream table for clues as to how much sand has eroded. Wood rots, rocks and other earth materials erode, metal rusts, and nylon mesh can ensnare living organisms. No. The strength and magnitude of the water is too great. broward county hands-on science Quarter 1 105

8 R EINFORCEMENT Have the students repeat the experiment to improve on their breakwater designs. Assessment Opportunity This Reinforcement also may be used as an ongoing assessment of students understanding of science concepts and skills. SCIENCE JOURNALS Have students place their completed activity sheets in their science journals. 106 activity 9 Shoreline Erosion C LEANUP Tell students to carefully tip and drain the water from their stream tables into the 1-L containers, then discard the water. Tell them to leave the sand, grid, and clay-filled grommet plug in each table, and to stack them for use in Activity 10. Have the students dismantle the breakwaters and discard all of the materials except the clay and the wooden sticks. The clay should be lumped together and placed in the reclosable bag. Rinse and air dry the other materials and return them to the kit.

9 Connections Science Extension The particles of water in a wave do not move forward with the wave but move upward and downward in a circular motion. Demonstrate this by having two students stretch a long rope along the floor. Then one student should move his or her end of the rope up and down repeatedly. Students will see waves move along the rope. Point out that the waves move forward but the rope itself moves only up and down. If you have a long container such as an aquarium or a wallpapering trough, you also could demonstrate wave action by floating small pieces of cork or aluminum foil on the surface of the water and pushing the water forward with a piece of cardboard at one end to form waves. Students will observe that the cork or foil pieces move up and down in place as the waves move along the length of the container. Encourage students to research wave motion and the terms that scientists use to describe the characteristics of waves. Such terms include crest, trough, wave height, wavelength, and period (the length of time for a wave to pass a given point). Science and Math Tell students that as waves approach the shore or any underwater object in their path, they begin to break when their height is 0.7 times the depth of the water, or when the water depth is 1.5 times the height of the waves. Create (or ask students to create) math problems based on these figures for the class to solve. For example, at what water depth will a 6-foot-high wave begin to break? (6 feet 1.5 = 9-foot water depth) If waves are beginning to break where the water is 20 feet deep, how high are the waves? (20 feet 0.7 = 14-foot wave height) Science and Language Arts Suggest that students write poems comparing a beach or coast on a calm day and during a storm. If students have not personally observed coastal wave action, discuss pictures they have seen on TV, including news reports of coastal storms. Encourage students to use words and phrases imaginatively to create images of the scene in listeners and readers minds. Give volunteers an opportunity to read their poems aloud. Science and Social Studies If global warming were to melt some of the Earth s water now locked in ice caps and glaciers, sea level would rise perhaps submerging major cities located along the Atlantic and Pacific coasts and in the Great Lakes region. Have students research the elevation of the downtown area of major U.S. cities to see how much of a rise in sea level would cause flooding of each city. Science, Technology, and Society Ask students to research and report on the various types of structures that are built to prevent or reduce shore erosion groins, jetties, bulkheads, breakwaters, revetments, and seawalls. Encourage students to make simple models of these structures. In areas directly affected by coastal storms, homes can be damaged or destroyed by battering waves and by the erosion of land. Often the homes are repaired or rebuilt, only to be damaged again in another storm. Ask students to research this issue and then debate whether rebuilding should be allowed in such areas. broward county hands-on science Quarter 1 107

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