After learning the basics of how the Grand Canyon was formed, students will investigate the canyon's layers and learn about the geologic time periods when they were deposited. They will conclude by writing newspaper articles from the perspective of scientists researching the canyon's layers.

Geography, earth sciences

Standard 7: "The physical processes that shape the patterns of Earth's surface"

Two to three hours

• Computer with Internet access

Students will

• read about and discuss how the Grand Canyon was formed;
• identify and describe the major rock layers of the canyon and their characteristics;
• describe the important characteristics of the geological era and period when a particular layer of the canyon was deposited; and
• pretend to be scientists studying a specific layer of the canyon and write articles telling the general public about their research.

Ask students if they know how the Grand Canyon was formed. Discuss their ideas as a class.

Have students read the National Park Service's Geologic Story at Grand Canyon. Ask them to look for the answer to the question "What are the two 'stories' of the Grand Canyon?"

Discuss students' answers to the above question, which will allow them to explain how the canyon was formed. They should understand that the canyon's layers were first deposited over hundreds of millions of years and that the Colorado River then carved the canyon out of those layers.

Have students go to the Grand Canyon Interpretation site and scroll down to the second diagram, which shows the Grand Canyon's layers with small illustrations of what the area might have looked like at the time each layer was deposited. Discuss the differences between the layers, as shown in these illustrations.

Ask students to scroll down to the section entitled "Geological Time." This section allows students to click on the canyon's layers to see drawings and read descriptions of the Grand Canyon region when each layer was deposited.

Ask students to click on each layer. On their own paper, have them write the following information: the name of the layer, its dates, the overall appearance of the landscape (or seascape, as it may be), and one or two species that lived at that time and place.

Divide the class into at least eight pairs or small groups, and assign each pair or group to one of the layers of the Grand Canyon (Kaibab/Toroweap Formation, Coconino Sandstone, Hermit Shale, Supai Group, Redwall Limestone, Muav Limestone, Bright Angel Shale, and Tapeats Sandstone). Make sure each layer is represented at least once in the classroom.

Have students go to the Web Geological Time Machine. Explain that this timeline shows a chronology of geologic time from 4,500 million years ago to the present. Inform students that geologic time is divided into eras and periods to make it easier to study discrete segments of time and to help classify the development of the earth and its life. Make sure they understand that "mya" on this timeline means "million years ago."

Ask students to locate the era when their assigned Grand Canyon layer was deposited (in the middle column), and have them click that era. Ask them to read about the era and answer these questions on paper:

• What are the dates of this era?
• What major events happened on earth during this era?

Have students use their browser's "Back" button to return to the timeline, and ask them to locate the specific period when their assigned Grand Canyon layer was deposited (in the right-hand column). Have them click on that period (e.g., Permian) and read about what occurred during that time. Ask them to answer these questions:

• What are the dates of this period?
• What major events happened on Earth during this period?
• What types of life is this period known for?

Have students go to Grand Canyon Explorer: The Geology of the Grand Canyon and scroll down slightly to see the Grand Canyon rock layers. Explain that the photograph on the left shows distinct layers of the canyon, while the diagram on the right shows the layers and their names. Ask them to spend a couple minutes trying to identify in the photograph the specific layer they've investigated. They can also click on the name of that layer to read more about it.

Ask each student to pretend he or she is a scientist who is planning to study the layer of the Grand Canyon that his or her group has investigated in this lesson. Have them write articles they might publish in a local newspaper to inform the general public about their research. Their articles should explaining the following:

• Why is this layer in the canyon in the first place? How did it get there, and why is it visible today?
• What were the climate and landscape like when this layer was deposited?
• What types of fossils might you expect to find in this layer?

• Have students return to Grand Canyon Explorer: The Geology of the Grand Canyon and click on "Where did all the rock come from?" Ask them to read this section and look for the answers to these questions:
  
  
  • What do plate tectonics have to do with the formation of the Grand Canyon?
  • Why were there oceans on the land where the Grand Canyon sits today?
  
  Ask students to write brief essays answering these questions.
  
  
• Have students read about the intentional flooding of the Grand Canyon at these Web sites:
  
  CNN: False Flood Unleashed on Colorado River
  The Colorado River: Water and the Desert
  USGS: Controlled Flooding of the Colorado River in Grand Canyon
  USGS: Grand Canyon Controlled Flood—Effects on Beaches
  
  Ask them to explain in paragraphs or a class discussion why the canyon is intentionally flooded, what the effects of this flooding are, and whether they think the flooding is a good idea.

Grand Canyon Explorer: The Geology of the Grand Canyon
Grand Canyon Interpretation
National Geographic: Grand Canyon—The Hidden Secrets
National Park Service: The Geologic Story at Grand Canyon
Web Geological Time Machine