Tides, High and Low

Explore how gravity and the moon affect tides. Find out how tides are useful to man.

• 1.

  If you have ever spent time at the beach, you probably noticed that the water rises slowly on the shore for six hours, then slowly recedes, or falls back, for another six hours. These movements happen twice a day and are called tides.

• 2.

  Tides are caused by the pull of the moon when it is directly overhead. That gravity is actually pulling the water toward the moon. In doing so, it causes the water to rise on the surface of the earth.

• 3.

  Why then, you may wonder, do we have high tides when the sun is out as well? What is actually happening is that the moon's gravity is pulling the water on the opposite side of the earth—the side that is having night while you are having day. That same gravity is pulling the earth away from the water on the side where you are standing.

• 4.

  At the shore, tides may rise from 6 to 8 feet, but in the middle of the ocean, the rise is much less and barely noticed.

• 5.

  Tides are useful to man. They keep harbors and seaports clean by carrying waste material' from the land out to sea, where it sinks to the bottom. Tides also make harbor entrances deep enough for fishing vessels and ocean liners to sail through.

• 6.

  In small groups, use Crayola® Model Magic® to create a relief sculpture based on what you have learned about tides. Use a large piece of plywood, thick foamcore, or thick cardboard as a base for your piece.

• 7.

  Find a clean area on the floor to work. Knead modeling compound thoroughly for best adherence. To create new colors, knead 2 primary colors until well mixed.

• 8.

  Press modeling compound firmly onto board. Use a rolling pin to roll out large flat areas. Push your thumbs and fingers into soft modeling compound after it is laid onto the board for interesting textures.

• 9.

  Model Magic that is fresh from the pack will stick to itself. Dried pieces can be glued together. After piece is completely dry, it may be displayed on a wall for all to see!

Benefits

• Students learn how gravity and the moon affect tides.
• Students find out how tides are useful to man.
• Students connect to create captivating relief sculptures using what they have learned about tides.

Adaptations

• Create mini relief sculptures on tiles. On each tile, represent an object that is directly related to what the students have learned about tides.
• Shrink this project down a few notches and make a seascape diorama. Use Model Magic to sculpt how the ocean looks at high and low tide. Have students give a presentation on how high and low tides occur.
• Assessment: Do students grasp the effect of the moon and gravity on tidal systems? Does the execution of their sculptures represent what they’ve learned? Did each student positively contribute to the group?