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Lesson 11
Forces of Nature: The Challenges of River Travel

Learning Objectives

Students will:

  • Define slope, gravity, velocity
  • Learn how rivers are formed
  • Collaborate to create their own river and apply forces of nature to alter a river
  • Explain how slope, gravity, velocity, and other forces affected the Lewis and Clark Expedition.


This lesson correlates to the national McREL standards located online at

Standard 1: Understands atmospheric processes and the water cycle
Standard 10: Understands forces and motion

Time Needed

It is recommended that five or six 45-minute class periods or three 90-minute class periods be scheduled to complete this lesson.


NOTE: In order to access and print Student Activity Sheets, you will need Adobe Acrobat. If you do not already have this tool, you may download Adobe Acrobat free of charge at the Adobe Web site.

  • A copy of Lewis and Clark: The Journey of the Corps of Discovery (To order, visit ShopPBS)
  • a television and VCR or DVD player
  • Lesson 11 Student Activity Sheet
  • Diatomaceous earth (available in 50 pound bags from swimming pool supply stores). Particle size and texture is critical to the success of the lab. Be sure it is the kind needed for swimming pool filtration. Swimming pool diatomaceous earth is bright white.
  • 15" long, 20" wide and 5" deep tubs such as those purchased from restaurant supply retailers. Standard dish tubs do not yield good results.
  • Remaining Lab Supplies (see Lab Group list below)

NOTE: Use sponges to blot up the water as the river is being formed inside the tub. While setting up your lab, wear a dust mask when the earth is dry, as it is an irritant. It is also advised that students wear eye protection. When the lab is completed, the diatomaceous earth inside the tubs can be stored until the next lab. Cover the tubs with large plastic trash bags, seal and store.

  • Materials Per Lab Group of 4-5 students:
    • 15 cups diatomaceous earth. Use swimming pool type only
    • 14+ cups water
    • paper towels and 4-5 sponges
    • blue food coloring (optional)
    • plastic tubs measuring 15" wide, 20" long and 5" deep
    • plastic coffee stir sticks
    • plastic cup
    • disposable dust mask
    • 2-3 blocks of wood
    • paper clips
    • Eye protection for each student
    • 1 large plastic trash bag with tie

Teaching Strategy

  1. Prior to student arrival in the classroom, write each of the terms below and their definitions on the board or overhead screen. Gravity, Slope, Velocity. Write each of these questions on a separate section of the board or overhead for use individually.

    • How are rivers and interstate highways similar?

    • Based on the map of the Missouri River and what you know about rivers, what problems do you think gravity, slope, velocity of the river, weather, and time of year might have caused for the Corps?

  2. Begin class by discussing the terms Gravity, Slope, and Velocity. Provide concrete examples to illustrate each term if possible. Explain to students that they will be learning about how gravity, slope, and velocity can form a river and alter it over time.

  3. Conduct the River Formations Lab using the guidelines below.

    1. Set out tubs. Wearing dusk mask, place 15 cups of diatomaceous earth into each tub. Add 14 cups water and mix together with hands. Test for consistency. It should be mushy with no puddling.

    2. Insert straightened paper clip into plastic coffee stirrer. Gently bend stirrer into half moon.

    3. Cut small notches into paper cup. Fill with water. Create a siphon in stirrer. Place into the notch in the paper cup filled with water.

    4. Experiment with slope by raising the tub with blocks of wood. Watch the "river" form through the diatomaceous earth.

    5. Have students record what their river looks like, noting and labeling features created during the experiment including water falls, caves, shallow lakes, canyons, shore line, smaller creeks, and tributaries.

    NOTES: Students should be encouraged to create as many experiments with river formations as possible. Students should also observe the rivers created by others. As land forms are being created (caves, smaller rivers, etc.) the features must be identified and labeled. Experiment with velocity by altering slope of the tub. At least one lab should have a totally flat slope to it, thus creating little velocity in the water flow.

  4. After completing the River Formation Lab, students should complete the Lesson 11 Student Activity Sheet. Facilitate discussion about the lab using the Activity Sheet.

  5. Next conduct a class brainstorming session a list to answer the question:
    How are rivers and interstate highways similar? Discuss answers as a group.

  6. Show students a map of the Missouri River (See Inside the Corps). Explain that is was President Jefferson’s goal to discover a Northwest Passage, and the Missouri River was the Corps “interstate” for exploring.

  7. Brainstorm as a class to answer the question: Based on the map of the Missouri River and what you know about rivers, what problems do you think gravity, slope, velocity of the river, weather, and time of year might have caused for the expedition?

  8. Before they view the film, direct students to prepare a notetaking sheet divided into the following categories.

    • Effects of Gravity, Slope, and Velocity on travel/navigation
    • Effects of weather and time of the year on travel/navigation
    • Effects of scenery and surroundings on the mood of corps members
    • Water-related features discussed in film (i.e. waterfalls, land marks, etc.)

  9. View the film and use notetaking sheets to record information for each category listed. Stop the video periodically to discuss relevant information about rivers.

  10. Conduct a final discussion and have students answer the question below citing specific examples from the film when providing answers. “What problems did gravity, slope, velocity of the river, weather, and time of year cause for the Corps?”

  11. Citing specific information learned from the lab and the film, have students create a 1-2 paragaph response to the following: “In your opinion, did gravity, slope, river, velocity, weather, or time of year have the greatest impact on the expedition?”

Assessment Recommendations

  1. Students could receive participation grades for completing the class discussions and the River Formation Lab.

  2. A completion grade could be given for finishing the Lesson 11 Student Activity Sheet and the notetaking activity related to the program viewing.

  3. Students could receive a letter grade based on a scoring guide or checklist for their written response activity.


Since the Corps of Discovery’s expedition, the role of rivers as a form of transportation, exploration, and commerce has changed in some ways and remained much the same in other ways. Have students create a graphic organizer such as a Venn Diagram that compares and contrasts the role of rivers at the time of the Lewis and Clark expedition and now. Have each student/group discuss and display their graphic organizer upon completion.