Modeling Weathering 1.6

Opener Why do you think rocks and rock formations have unique characteristics?

Guiding Question How does rock form on and below the surface of Earth?

Last time on As the World Forms… In the last class, you observed different rocks and rock formations found in the Grand Canyon. You noticed that rocks have different characteristics, such as color and texture. One reason different rocks have different characteristics is that they form in different ways on and below the surface of Earth. Over the next few classes, we’ll be making a model of the processes involved in rock formation—both above and below the surface of Earth—to understand more about why different rocks have different characteristics.

Model An object, diagram, or computer program that helps us understand something by making it simpler or easier to see. It’s difficult for geologists to observe the processes that form and change rock because those processes happen over very long periods of time. Models are a great way to understand something that is impossible to observe directly

Examples of models

Examples of models

Examples of models

Modeling Weathering Today, we’re going to make a model of different processes that form different kinds of rock on the surface of Earth. Using real rocks to investigate this would be very difficult because one characteristics of rocks is that they form VERY SLOWLY. So instead, we will use life saver candies to represent large pieces of the same type of rock

Compare and contrast What characteristics do the rock sample and candies have in common? What characteristics are different?

Rock can be weathered. Weathering is when rock is broken down into smaller pieces by natural processes. This can happen because of forces acting on the rock on the surface of Earth. One of these forces can be wind.

Quick Demo of Weathering In our model, you will represent the forces of weathering by shaking a jar with the candies in the jar. How is this motion to model weathering similar to and different from the images of weathering you just saw?

DO NOT EAT! Safety Guidelines Even though the candies are edible, they are being used with science equipment that may have touched substances that are not edible! DO NOT EAT!

Instructions Each group member should shake their group’s jar for one minute, for a total of four minutes of “weathering.” In your journals, briefly describe what happened to the candy as a result of the weathering and how it compares to the candy you left in the plastic bag.

Time We only “weathered” our candies for four minutes. Actual weathering can take years, decades, centuries, and even longer! Some rock is harder than others to break down.

Show and tell – Sediment edition Share your observations of the candy “sediment.” Sediment can be different sizes, shapes, etc. What do you think would happen with more time for shaking?

Next step Pick out all the large chunks of candy remaining in the plastic jar and dispose of them. (The sedimentary rock formation model you will create next works best if only fine sediment remains.) Carefully pour all the remaining fine sediment into the empty plastic bag. Write the names of all group members on the adhesive label and adhere the label to the bag.