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Overview:
In this lesson, students will learn about how the Grand Canyon was formed, focusing on how the process of erosion enabled its rock layers to be deposited. They will examine the canyon's layers to see what the area probably looked like when the layers were created. Students will conclude by creating posters illustrating and describing what the Grand Canyon looks like today and what it looked like when one of its layers was formed.
Connections to the Curriculum:
Geography, earth sciences
Connections to the National Geography Standards:
Standard 7: "The physical processes that shape the patterns of Earth's surface"
Time:
One to two hours
Materials Required:
- Computer with Internet access
- Map of the United States, showing the location of the Grand Canyon
- A large rock (optional)
Objectives:
Students will
- locate the Grand Canyon on a map;
- brainstorm how the Grand Canyon might have formed;
- view a Web site to help them understand the concept of erosion;
- analyze a photograph of the Grand Canyon's rock layers;
- view and discuss drawings of the Grand Canyon region as its various layers were deposited; and
- create posters showing what the Grand Canyon looks like today and what it looked like when one of its layers was deposited.
Geographic Skills:
Acquiring Geographic Information
Organizing Geographic Information
Answering Geographic Questions
Analyzing Geographic Information
S u g g e s t e d P r o c e d u r e
Opening:
Development:
Write the word "erosion" on the board, and ask students if they know what it means. Discuss their ideas and then tell them it means, "the way that material such as sand and rock is worn away from the earth's surface." One example of erosion is when the ocean's waves, over time, change the way rocks along the coastline look by washing away little pieces of the rocks. Erosion can be caused by water, wind, chemicals, or the ice in glaciers.
As an option, show students a large rock and have them hypothesize how it might have changed due to erosion.
Have students read about how sedimentary rock is formed. Ask them to read this page and look at the animation. Help them make sense of what's going on in the animation: water and wind erode rock, rain washes pieces of the eroded rock into a body of water, and the water deposits these rock pieces in successive layers.
Explain that rivers, lakes, and oceans all have small pieces of sand and rock that float in the water and are carried by the currents. When they settle on the bottom of the river, lake, or ocean, they might stay there and be buried by other pieces of rock or sand. Each of these layers that are left on the bottom has the color and texture of the rock and sand that was left there.
Have students look at the photograph of the Grand Canyon again. Explain that each of the layers they see was deposited in the manner they've just learned about. How many different layers can they count? How many different colors do they see in the layers? Why do they think the layers look different from each other? Students should recognize that the layers are different because different types of rocks and sand were deposited at different times.
Ask students if they can find the Colorado River at the bottom of the canyon in this photograph. Explain that over several million years, this river eroded the rock layers and made it possible for us to see them. The river once flowed at the top layer but now flows where we see it today.
Closing:
Explain that the climate and landscape of northern Arizona were very different when the canyon's layers were forming than they are now. During much of that time, the canyon was covered with water.
Have students see examples of what the Grand Canyon region looked like at different periods of its development. Explain that the layers shown here are the major layers of the canyon. Each one has a special name.
Ask students to click on a few of the layers to see what the area looked like at those times. Discuss the types of animals and plants they see, and compare and contrast the scenes to the desert environment of northern Arizona today. (They can refer to the pictures of the Grand Canyon's current landscape at National Geographic or National Parks of the American Southwest.)
Suggested Student Assessment:
Assign each student or group to choose one layer of the Grand Canyon, as seen at Grand Canyon Interpretation. Make sure each layer is assigned at least once in the classroom.
Have students draw posters illustrating the things listed below. They should also write captions describing them.
- What does the Grand Canyon look like today (one drawing on part of the poster) and why does it look this way (described in a caption)?
- What did the area that is today the Grand Canyon look like when the students' assigned layer was being deposited, including the plants and animals (a second drawing on another part of the poster)?
As an option for the upper grades, have students draw arrows from their second drawings (what the layer looked like in the past) to the approximate location on their drawing of the canyon today where that layer exists. They do not have to be precise but should estimate the location of the layer.
Have students share their posters with the class and describe the layers they investigated.
Extending the Lesson:
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