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Activity: Sea Level and Gravitational Flow
NGSS Science and Engineering Practices
NGSS Crosscutting Concepts
NGSS Disciplinary Core Ideas


  • Transparent plastic cup
  • Nail or sharp pencil
  • Masking tape
  • Transparent plastic shoe box
  • Ruler
  • Food coloring
  • Coins or other weights



Image caption

Fig. 3.21. Setup for the Sea Level and Gravitational Flow activity

Image copyright and source

Image by Byron Inouye

  1. Predict what will happen when a cup with a hole in the side is filled with water to a level above the level of water in a box (Fig. 3.21 A). Record your predictions.
  2. Carefully punch a hole in the plastic cup as shown in Fig. 3.21 A. The height of the hole should be about halfway up the side of the cup.
  3. Test the system by carrying out the following steps:
    1. Cover the hole with masking tape. Leave an unattached flap so that the tape can be easily removed.
    2. Fill the box two-thirds full tap water.
    3. Place coins in the bottom of the cup so it does not float.
    4. Fill the cup with colored water to a level a centimeter or more above the level in the box.
    5. Pull off the masking tape and sketch your observations. Observe for at least two minutes.
  4. Set up the system as shown in Fig. 3.21 B. Repeat the procedure step 2, except fill the cup so that the water level is a centimeter below the water level in the box.


Activity Questions
  1. Explain why the water flows as it does in systems A and B.
  2. How might the conditions shown in systems A and B be produced in the ocean?
  3. The Atlantic ocean basin has a lower average sea level than the Pacific ocean basin.
    1. Which system is modeling the Atlantic ocean basin? The Pacific ocean basin?
    2. The Atlantic and Pacific ocean basins meet near Antarctica. How do you think the water is flowing in this area? (Bonus: Research the water flow around Antarctica to further your knowledge about this area of the world ocean.)
  4. The major ocean basins on Earth have large circulation cells called gyres. Gyres pile water in the center of their circulation.
    1. Which system is modeling a gyre?
    2. How does a gyre affect water flow?
Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.