Transcript Day 46
Day 46 In the Grand Canyon, there is a layer of Coconino Sandstone directly above a layer of Hermit Shale. Which layer is older? Why? The Hermit Shale is older. When sediments form layers, new layers form on top of old layers. The Hermit Shale is older because the Coconino Sandstone formed on top of it. Daily Warm-Up Exercises 1 Relative Scale and Magnification Exercise 3.3 2 Colorado Plateau Map 3 Color in Diagrams Exercise 3.4 4 Colorado Plateau Map 5 Colorado Plateau (Part 3) Investigation 3 Grand Canyon Rocks 6 Discuss Fossils Turn to Grand Canyon Rock Lineup (lab notebook, page 13). The Kaibab Limestone layer is about 8000 feet above sea level. What did you observe in your sample of Kaibab Limestone? fossils of sea shells How can you explain fossils of sea shells at such a high elevation? The layer formed under an ocean and was later uplifted and exposed by erosion. 7 Introduce the Colorado Plateau A plateau is a large, nearly level area of land that has been uplifted (elevated) above the surrounding area. The Grand Canyon is part of the Colorado Plateau. It extends over four states. What states are they? Arizona, Colorado, New Mexico, Utah 8 Surface Layers Geologists that study the Colorado Plateau produced maps that show which rock layers are exposed at the surface. The Kaibab Limestone Layer is at the surface in several areas within this boundary. 9 Deeper Layers If we drilled a hole into the Kaibab Limestone in this area, what layer do you think we might find underneath? Toroweap Limestone What layer would you expect to find under the Toroweap Limestone? Coconino Sandstone 10 Survey Rock Columns Turn to page 33 in the Resources book. This chart shows the sequence of rock layers that are visible at six national parks. A sequence of layers is called a rock column. The top layer in each column is exposed at the surface in that park. 11 Survey Rock Columns Do you see any rocks on this chart that you recognize from the Grand Canyon? Kaibab Limestone in Zion Park Where is Zion Park in relation to the Grand Canyon? To the north, just over the Utah border. 12 Cedar Mountain There is a butte called Cedar Mountain at the South Rim of the Grand Canyon. The exposed rock below the butte is Kaibab Limestone. If Kaibab Limestone is directly below the butte, what kind of rock is the butte made of? Moenkopi Formation, like the sequence in Zion National Park. 13 Formation A formation is a rock layer that is made up of more than one kind of rock. Kaibab Limestone is often called the Kaibab Formation because, although it is mostly limestone, it does contain a little sandstone. Kaibab Formation is more correct, but Kaibab Limestone is widely used. 14 Moenkopi Formation The Moenkopi Formation is made up of mostly mudstone with a little sandstone. According to the chart, in which national parks is the Moenkopi Formation visible? Zion, Canyonlands, Arches, Petrified Forest What else do those parks have in common? They all have the same sequence of layers above Moenkopi. 15 Moenkopi Formation Why is there no Moenkopi Formation at Bryce Canyon? There might be a Moenkopi Formation buried below the Navajo Sandstone, but it hasn't been exposed yet. Maybe someday it will be visible there as well. 16 Self-Assessment Reread your Quick Write from day 41, which was about this question: Why are there lines on the walls of the Grand Canyon? If your ideas have changed, explain how. If your ideas are still the same, explain how what you've learned supports them. 17