Lesson Plan: Warming drops Great Lakes to historic lows

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Objectives

• Students will construct and explain theories for the decline in water level in the Great Lakes.

Standards

Benchmarks for Science Literacy

By the end of the 12th grade, students should know that

• A system in equilibrium may return to the same state of equilibrium if the disturbances it experiences are small. But large disturbances may cause it to escape that equilibrium and eventually settle into some other state of equilibrium.
• Insist that the critical assumptions behind any line of reasoning be made explicit so that the validity of the position being taken-whether one's own or that of others-can be judged.

National Science Education Standards

• CONTENT STANDARD A: As a result of activities in grades 9-12, all students should develop
  • Abilities necessary to do scientific inquiry
  • Understandings about scientific inquiry
• CONTENT STANDARD F: As a result of activities in grades 9-12, all students should develop an understanding of:
  • Natural resources
  • Natural and human-induced hazards
  • Science and technology in local, national, and global challenges:
  • Natural ecosystems provide an array of basic processes that affect humans. Those processes include maintenance of the quality of the atmosphere, generation of soils, control of the hydrologic cycle, disposal of wastes, and recycling of nutrients. Humans are changing many of these basic processes, and the changes may be detrimental to humans.
  • Materials from human societies affect both physical and chemical cycles of the earth.

Procedures

1. Have students locate the Great Lakes on a map. Have them look at other lakes on an international map to compare their size to other lakes. Ask students to list ways in which bodies of fresh water are important to human populations.

2. Discuss global warming as an issue to discover what students already know about polar cap melting and water evaporation. Have students hypothesize what might happen in the short term if global temperatures continue to rise. Remind them that many scientific experts believe that water levels will rise as a result of global warming, due to melting at the polar caps.

3. Have students read the CNNfyi story, "Warming Drops Great Lakes towards Historic Lows"

4. For review ask:

• Where are the Great Lakes? Why are they in the news?
• What are the positive and negative effects of lower water levels on business on and near the Great Lakes? The environment? Recreation?
• How far below the average water mark are current water levels?
• What are the suspected causes of the declining water level?

5. Ask students to consider these seemingly contradictory events: water is evaporating and levels are declining in some places in the wold, such as the Great Lakes region. At the same time, polar melting is occurring, creating an increase in water. Scientists have theorized that this warming trend will raise water levels.

6. Group students and have them develop a theory to explain the water level decline in the Great Lakes. Have them search for evidence to support their theories. Each group is required to have at least three pieces of supporting evidence for its theory.

7. Have each group present its theory to the class, and have the class subject the theory to scientific scrutiny.

Assessment

Have the groups develop ways to test their theories. Carefully examine the tests for controlled and manipulated variables.