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6-8 > Ecology
Grade level: 6-8 Subject: Ecology Duration: 2 class periods
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Objectives | Materials | Procedures | Adaptations | Discussion Questions | Evaluation | Extensions | Suggested Readings | Links | Vocabulary | Academic Standards | Credit
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Objectives
 



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Grand Canyon: Our Geologic Past




Students will understand the following:
1. Damming of a river can have both helpful and harmful effects on the ecology of an area.
2. Opening a dam to allow controlled flooding can reverse some of the harmful effects of damming.
3. The Glen Canyon Dam has held back the Colorado River's flow since 1963, reducing flooding and sediment deposit in the canyon.
4. In 1996, the Glen Canyon Dam was opened to create an experimental controlled flood, the effects of which scientists are still evaluating.
Materials

For this lesson, you will need:
map of the United States
computer with Internet access
print material concerning damming and controlled flooding, and the Glen Canyon Dam in particular
Procedures

1. Locate the Grand Canyon on a map of the United States for your students. Then share the following background information with the class:
  • The Glen Canyon Dam is located upriver from the Grand Canyon. Since 1963, it has held back the Colorado River’s flow, which has reduced flooding and sediment deposit in the Grand Canyon, leading to environmental changes such as reduced beach habitat for plants and animals.
  • In 1996, the Glen Canyon Dam was opened to create an experimental controlled flood. Scientists are still studying the effects of this flood on the Grand Canyon.
2. Have students research the reasons for the 1996 flooding, the changes caused by the flood, and the results of the flooding experiment so far. The following Web sites will help them in their research:
3. Ask your students to imagine that they are scientists responsible for recommending whether more controlled flooding should be done in the future. Have them meet in small groups to discuss the pros and cons, basing their discussions on the research they have done.
4. Have each student write a proposal that includes the following components:
  • an overview of the 1996 controlled flood, including a justification for it and an explanation of what happened to the river and riverbanks during the flood
  • a summary of some of the changes that have been noticed in the Grand Canyon subsequent to the flood
  • a recommendation as to whether controlled flooding should become a regular practice.
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Adaptations

Instead of having younger students conduct research independently, provide them with downloaded or printed material from the recommended Web sites. Also, younger students might write their proposals in their groups, rather than individually.
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Discussion Questions

1. Discuss why the Grand Canyon’s layers are different colors. What types of materials might give the layers their color?
2. Discuss the clues you can look for in rock formations near your home. What might local rocks be able to teach you about the climate and landscape of your region’s past? What evidence do you think you might find if you started to carefully examine your local rocks?
3. Hypothesize the reasons why the Grand Canyon region of northern Arizona has experienced several dramatic changes in climate over many millions of years. Explain how the movement of the Earth’s tectonic plates might affect the climate of a particular body of land such as northern Arizona.
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Evaluation

You can evaluate your students on their proposals using the three-point rubric:
Three points: Proposal includes all components required by assignment, clearly written explanations, recommendation well-reasoned and backed up with compelling, concrete evidence.

Two points: Proposal includes most components required by assignment, clearly written explanations, recommendation well-reasoned and backed up with some evidence.

One point: Proposal includes few components required by assignment, adequate explanations, recommendation lacks sound reasoning, recommendation backed up with some evidence.

You can ask your students to contribute to the assessment rubric by determining what constitutes a clear explanation and establishing criteria for adequate evidence.

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Extensions

Grand Canyon Historical Diagrams
Have your students use a large piece of poster paper or five smaller pieces of paper to draw a five-part chronological diagram of the rock layers that can be observed in the Grand Canyon. The first part should illustrate the rock as it might have appeared 1 billion years ago. The second and third should depict the rock layers during periods when the canyon was under the sea and when the climate was desert. The fourth section should illustrate the canyon as it appears today. The fifth section should depict how the canyon might look 250 million years from now. In addition, ask students to include the approximate dates and a one- or two-sentence caption next to each illustration. Students will need time to use the Internet and the library to research the canyon’s appearance during each of these time periods. Make sure that they understand that the Colorado River didn’t start carving through rock layers to create the Grand Canyon until approximately 20 million years ago, so they should not include the river in the earlier diagrams.

Grand Canyon Brochure
Ask your students to write brochures for Grand Canyon visitors who are interested in learning about the canyon’s geology and history. Students will first need to research the geology and history of the canyon. They should then create brochures that describe how the canyon was formed, why its layers look so different from one another, and what its layers can tell us about the climate and landscape of northern Arizona throughout the millennia. The brochures should include diagrams and pictures to illustrate their written explanations.

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Suggested Readings

A Grand Canyon Journey: Tracing Time in Stone
Peter Anderson. Watts, 1997.
Excellent maps, diagrams, and photographs make it easy to understand the numerous, diverse layers of the Grand Canyon. Accompany the author as he hikes along Bright Angel Trail and passes rocks formed during the last 1.7 billion years.

“Climate at the Bottom of the Grand Canyon”
Diana Stanitski-Martin, Melvin G. Marcus, J. Anthony Brazel, Nancy J. Selover, and Randall S. Cerveny.Focus,Winter 1999
The controlled releases of water from Lake Powell down the Colorado River and through the Grand Canyon result in the river maintaining a nearly constant temperature. This has caused changes in the climate, which in turn has altered the flora and fauna. This team of scientists describes its quarterly observations at meteorological stations along the canyon.

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Links

Grand Canyon Explorer
An interesting site with much diverse information onThe Grand Canyon. It is well organized and user friendly

Grand Canyon National Park
Provides general information on trails and wildlife of the Grand Canyon

Grand Canyon National Park Foundation
Historical background information as well as current news about the park is provided

Theodore Roosevelt
A short description of the life of Teddy Roosevelt

Controlled Flooding of CO River in the Grand Canyon: The Rational and Data Collection
Detailed information on the flooding of the Colorado River near the Grand Canyon

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Vocabulary

Click on any of the vocabulary words below to hear them pronounced and used in a sentence.

speaker    brachiopod
Definition:Any of a phylum of marine invertebrates with bivalve shells within which is a pair of arms bearing tentacles by which a current of water is made to bring microscopic food to the mouth.
Context:Brachiopods are ancient shellfish that have been found in the layers of the Grand Canyon.

speaker    erosion
Definition:The action or process of wearing away by the action of water, wind, or glacial ice.
Context:Wind, water, or ice can cause erosion of sedimentary rock, resulting in some of the rock being broken down into smaller pieces and carried away.

speaker    limestone
Definition:A rock that is formed chiefly by accumulation of organic remains, consists mainly of calcium carbonate, is extensively used in building, and yields lime when burned.
Context:Because limestone contains tiny bits of shell, its presence indicates the existence of an ancient sea.

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Standards

This lesson plan may be used to address the academic standards listed below. These standards are drawn from Content Knowledge: A Compendium of Standards and Benchmarks for K-12 Education: 2nd Edition and have been provided courtesy of theMid-continent Research for Education and Learningin Aurora, Colorado.
 
Grade level:3-5, 6-8
Subject area:science: earth and space
Standard:
Understands basic Earth processes.
Benchmarks:
Benchmark 3-5:
Knows that smaller rocks come from the breakage and weathering of bedrock and larger rocks.
Benchmark 3-5:
Knows how features on the Earth’s surface are constantly changed by a combination of slow and rapid processes (e.g., weathering, erosion, and deposition of sediment caused by waves, wind, water, and ice; sudden changes in the landscape caused by landslides, volcanic eruptions, and earthquakes).
Benchmark 3-5:
Knows that fossils provide evidence about the plants and animals that lived long ago and the nature of the environment at that time.
Benchmark 6-8:
Knows processes involved in the rock cycle (e.g., old rocks at the surface gradually weather and form sediments that are buried, then compacted, heated, and often recrystallized into new rock; this new rock is eventually brought to the surface by the forces that drive plate motions, and the rock cycle continues).
Benchmark 6-8:
Knows that the Earth’s crust is divided into plates that move at extremely slow rates in response to movements in the mantle.
Benchmark 6-8:
Knows how landforms are created through a combination of constructive and destructive forces (e.g., constructive forces such as crystal deformation, volcanic eruptions, and deposition of sediment; destructive forces such as weathering and erosion).
Benchmark 6-8:
Knows how successive layers of sedimentary rock and the fossils contained within them can be used to confirm the age, history, and changing life-forms of the Earth, and how this evidence is affected by the folding, breaking, and uplifting of layers.

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Credit

Betsy Hedberg, former middle school teacher and current freelance curriculum writer and consultant
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