Introduction: Discover Geological Folds With Homemade Playdough
How do you think the Grand Canyon was formed? What about a mountain or a hill? It all comes back to layers and how they are compressed.
Our Earth is made of layers. It has, overall, four layers based on chemical variations: the solid crust on the outside, the mantle, the outer core and inner core. Another one our projects goes into more detail, but in this project, we are discussing the Earth’s crust and especially the sedimentary rocks found near the surface.
Sedimentary rocks are often found in layers. Think of the Grand Canyon, where the rock layers are exposed like a layer cake. Each layer is made of sediments that were laid down (or deposited) in a certain environment such as a sand dune or lakebed. Sediments are deposited horizontally; the lowest layers are the oldest and the highest layers are the youngest.
In this project, we will be learning about geological folds using playdough!
Compressive stress can make rocks form or crumple into folds. Folds are bends in the rock. We are going to make folds with playdough because as in layered sedimentary rocks, you can trace the folding of the layers with your eyes, just like we will see in the playdough!
● Playdough (can also be made using supplies below)
○ Food Coloring
○ Mixing bowl
○ Measuring cups
● Rolling pin
● Table covering/cutting board (to protect table)
● 2 blocks or items to push together.
Step 1: Prepare Your Playdough
Using this link: https://www.instructables.com/id/No-Bake-Playdough/ for a large batch made for 4+ people see below for smaller batch measurements. .
Follow the directions on how to mix, but with the modified measurements below to make smaller batches per color. Remember, you might need to add more or less of each ingredient depending on your brands of supplies or what color you are mixing. Red dye makes the dough sticky sometimes, if your dough is sticky add extra flour. If your dough is dry add oil.
Medium batch for 2+ people
● ½ cup of water
● 8+ drops of food coloring
● 1 cup of flour
● ¼ cup of salt
● 2 tbs of oil
Small batch for 1+ people
● ¼ cup of water
● 5+ drops of food coloring
● ½ cup of flour
● 4 tbs of salt
● 1 tbs of oil
I made 5 small batches to represent layers of sedimentary rocks. I made the following colors: white (no food coloring), green, red, yellow, and mixed all to make a brown. For this project you would only need 2 to 3 small batches of different colors, I made more colors for multiple projects.
Step 2: Divide Your Playdough, Roll Out Your First Layers, and Stack Them
Divide and roll your colors into balls, I made sure to have 2 balls per color, for a total of 10 balls and 10 layers. After you have divided them, take one playdough ball, press it down and use your rolling pin to make a long layer of dough. Repeat with a different color. Put one color on top of the other color to create your first two layers.
Step 3: Add More Layers!
Keep adding layers, remembering to alternate colors so that no two layers are the same color, until you have used all your playdough or until your stack is how you want it.
Step 4: Cut the Sides of Your Layers Off to Make a Skinny Rectangle
Using your knife, carefully cut off the excess on each side to make a long skinny rectangle. This rectangle is now your land mass where you will be able to see the layers when you compress them.
Step 5: Compress Your Layers!
This is when you will need your two blocks or items to compress. Put a block at each end of your rectangle and using both hands, slowly compress or push the blocks toward each other. The blocks being compressed create a type of stress on the playdough, which causes a deformation, or in this case a fold.
Step 6: Determine Which Type of Fold You Made.
There are three types of folds: monoclines, anticlines, and synclines. A monocline is a simple bend in the rock layers so that they are no longer horizontal but are incline.
However, an anticline, like how this project occurred, is a fold that arches upward. The rocks dip away from the center of the fold.
A syncline is a fold that bends downward. The rocks curve down to a center. Sometimes an anticline and syncline can happen in the same geological feature!
Remember, unlike playdough, once rocks are folded, they do not return to their original shape. If rocks experience more stress, they may undergo more folding, or even a fracture.
Also feel free to take a look at our other instructables for more science activities and experiments!
https://www.instructables.com/member/Sciencecityed/ And for more information about Science City, visit https://www.unionstation.org/sciencecity or follow us on Facebook @ScienceCityKC. Remember, to tag us or hashtag #ScienceCityKC.