The foundation of an estuary is the movement of water. Water moves as a result of tides, wind and rain. The water in an estuary varies from salt to fresh along a continuum. The closer one gets to the Atlantic Ocean, the saltier the water. The closer one gets toward the headwaters of the Chesapeake Bay (The Susquehanna River) the fresher the water will be. The chemistry of the water determines which plants and animals will live there. This activity is designed to help students understand the movement of water into and out of the estuary.  It also demonstrates where fresh water and salt water meet (the convergence zone) producing distinct water conditions. 

Objectives

• Students will demonstrate the movement of fresh water in an estuary.
• Students will demonstrate the movement of salt water in an estuary.
• Students work together to role play tidal movements and create a convergence zone.

Materials

• A drum or other musical instrument to produce a rhythm.
• Students acting as water molecules.
• Teacher Leader
• Sides of the room marked as fresh water and ocean water.
• Video camera if you wish to tape your students during the activity.
• A room with a plenty of space.
  

Procedure

Four conditions will be modeled in this activity: tides moving back and forth, fresh water tidal movement, salt water tidal movement and a convergence zone.  

Tides

• Have students form a single line.   
• Students move 3 steps to the right in a step together step motion, indicating tidal movement downstream.
• Students move 3 steps to the left in a step together step motion, indicating tidal movement upstream.
• Continue this motion until students understand flood and ebb tides. (Flood tide: water moving in from the ocean, Ebb tide: water moving out of the estuary toward the ocean)
  

Fresh Water Tidal Movement

• Keep students in a single line.
• Designate one side of the classroom the “ocean” side of the estuary and the other side of the classroom as the “river” side of the estuary.
• Students move in a step together step motion toward the ocean side of the room. This is a very slow movement.

Salt Water Tidal Movement

• Keep students in a single line
• Students move in a step together step motion toward the river side of the classroom in a slow movement.  

Convergence Zone

This zone is created from a combination of tidal movement and freshwater flow from the land.

• Divide the class into two lines.
• Separate the two lines with a distance of approximately 5 feet between the two lines.
• One half of the class will represent the ocean tidal movement toward the land.
• The other half of the class will represent fresh water movement from the land toward the ocean.
• Students move in a step together step motion towards each other.
• The two lines should move three steps towards each other and one step back representing tidal movement.  
• Students continue this movement in the two lines until the lines eventually come together and mix. This mixing area is the convergence zone.

National Science Education Standards

9-12 A: Science as Inquiry

• Abilities necessary to do scientific inquiry
• Understandings about scientific inquiry

9-12 B: Physical Science

• Motions and forces
• Interactions of energy and matter

9-12 C: Life Science

• Matter, energy, and organization in living systems 

9-12 D: Earth and Space Science

• Energy in the earth system

9-12 G: History and Nature of Science

• Nature of scientific knowledge

Lesson Resources

Scenario Diagrams