Printable Version for your convenience!

Teacher's Guide: Formation of a Canyon

Theme: Patterns of Change Content Area: Earth Sciences Grade Level: 4 - 6

.

.

Note from LessonPlansPage.com: This lesson makes use of some student handouts and a video that are no longer available because the plan's original author has taken them down from their website. The lesson has been left here as it may have some value to you without these materials.

Learning Goals:

At completion of this unit, students will demonstrate their understanding of the processes which contribute to the evolution of sandstone canyons by:

• participating in a geologic modeling activity.
• answering questions similar to those found on nationally normed standardized tests.
• applying concepts learned in this unit to a new situation by completing a short writing assignment.

Background:

The formation of sandstone canyons is a result of change over time. The changes that have resulted in the formation of Zion Canyon can be classified into three processes.

Through the process called sedimentation, layers of rock are formed one on top of another. Geologists know that to go back in time they must dig deeper into the earth's crust. In Zion National Park, the digging has already been done by the river. The oldest rocks are in the shale layer at the bottom of the canyon. The shale is softer than the neighboring sandstone because it was formed from muddy swamps.

Next comes several layers of sandstone formed from the sand dunes of the Jurassic period. The middle layer is the hardest because it contains more minerals which help to cement the grains of sand together. One of these minerals is iron oxide, commonly known as rust. The iron oxide gives this hard middle layer its deep red color.

The top layer of Navajo sandstone is softer and whiter because it lacks iron oxide and several other minerals that help hold the sand grains together. Scientists believe that over time these ancient dunes were covered, perhaps several times, by an inland sea.

Later, through a geologic process called uplift a large area was raised high above sea level. The area that was raised is called the Colorado Plateau. Some parts of the plateau have been raised more than 10,000 feet. The Colorado Plateau is still on the rise today.

The rise in elevation made yet another process possible: erosion. As the river cuts through the layers, a predictable pattern occurs: 1) the soft white Navajo sandstone is left standing to be shaped by other forces of erosion, 2) the harder red sandstone layers form vertical surfaces which support the walls of the canyon until, 3) the soft shale layer at the bottom washes away and the layers above fall into the ever widening canyon.

Learning Activities:

Introduction of the Theme (class discussion)

Introduce the theme of Patterns of Change by asking the students to make a list of various changes that have occurred over time.¹ The discussion should include changes from all areas of science; changes in animal habitats, changes in volcanoes, or changes that happen during nuclear fusion can all qualify as change over time. This activity can be handled as a whole-class activity or in small groups. The discussion time should be limited to 5 minutes, after which a list should be compiled at the blackboard.

Preparing to Visit the Park (kinesthetic activity)

Explain that one change that you know about is the way that sandstone canyons evolve. Give each student paper and crayons and guide them through the following activity.

Have the students turn their papers sideways (long side horizontal). Ask them to draw 2 lines dividing the paper in 3 parts. The bottom layer is to be labeled "shale", the middle layer "hard red sandstone", and the top layer "white Navajo sandstone." Have the students color the shale brown, the red sandstone red or red-orange, and leave the Navajo sandstone white.

Have the students follow your lead as you tear the paper in a precise manner while relating the following: The river cuts through the layers of sandstone until it reaches the shale (tear a "V" shape out of the paper to match this description). The shale, weakened by seeps and springs, falls away (starting at the point of the "V" tear an oval out of the shale layer). Pieces of sandstone fall and the canyon grows wider (tear pieces from above the oval where the shale is missing).

Geology Field Trip (video)

Encourage the students to imagine they are visiting Zion National Park as part of a geology excursion. Ask them what they expect to find there. Allow them to take notes during the video which they can share with the class at the conclusion of the presentation. The video is 30 minutes long.

Using the Handouts (reading for information)

The handouts are designed to be used individually or in groups. If the students are unfamiliar with making an outline some discussion might be helpful after they read the section called "What Scientists Already Know."

Verbally ask the students the following questions before they attempt to fill in the outline:

1. What are the three geologic processes that formed the layers of rock? (sedimentation, uplift, and erosion) (Point out the fact that these important terms are underlined in the reading selection so that they will be able to refer to them easily.)
2. What are the names of the layers of rock? (white Navajo sandstone, red sandstone, and shale)
3. Where does the red color come from? (iron oxide)
4. What happens when the shale weakens? (the sandstone above falls into the canyon and the canyon gets wider)

Revisiting the erosion process (video segment)

On the second page students have a chance to use their powers of observation. Explain that when scientists revisit an area, it is usually because they are looking for something. It is a good idea to have the students look through the exercises before viewing the video segment so they will know what they are looking for, but they should refrain from marking any answers until after the area has been "revisited". The video segment is called "Watercourse". It is the first "music video" found near the beginning of the tape.

Evaluation and Assessment (model, quiz, and synthesis)

The final section on page 2 of the handout is an activity which can be used as part of the assessment process. The skills used in constructing the model are not as important as the student's response to the model. If it works, why does it work; if it's not at all like the real thing, what is different? In making these justifications, the student is expressing his or her understanding of the formation of sandstone canyons.

The quiz contains 6 questions. The first 5 are similar to standardized tests in content and format. Number 6 is an example of the newer "authentic assessment" type of testing. Here is the answer key:

The rubric for number 6 is as follows: