This activity was included in our Soil Science Discovery Kit in summer 2020 for teens ages 13-18. We are making one activity from each age group available for all to enjoy.

When you dig deep into soil, there are different layers called soil horizons. The layers are called “horizons” because they spread from side to side (horizontally). Each layer is different from the others. During today’s activity, you will learn more about soil horizons.

Materials

  • Small package of Oreo cookies
  • Small plastic zip-close bag 
  • Vanilla pudding cup
  • Chocolate pudding cup
  • Coconut sprinkles
  • Gummy worms
  • Plastic spoon
  • Clear plastic cup
  • Rolling pin

Instructions

  1. Gather the materials listed above and place the contents on the table. 
  2. Put the clear plastic cup in front of you.
  3. Open the Oreo cookie package and remove one Oreo.  
  4. Place the Oreo on the bottom of the cup. This represents bedrock.
  5. Place two cookies in the small zip-close bag. Place them in the bag so they lie flat on the table.
  6. Use the rolling pin to crush the cookies into small pieces.
  7. Open the bag and pour the crumbs into the cup on top of the whole cookie. This layer represents the parent material.
  8. Open the vanilla pudding and use the spoon to put three scoops of pudding on top of the cookie crumbs. This represents the subsoil.
  9. Open the chocolate pudding and use the spoon to put three scoops of chocolate pudding on top of the vanilla pudding. Add a gummy worm to the pudding. This layer is called the topsoil.
  10. Open the coconut sprinkles and place them on top of the chocolate pudding. This layer represents the organic/litter material.

The final product should look like the diagram to the right (text in the image is included below).

An inverted pyramid diagram representing edible soil layers. Text on the image is represented on the page.

  • Bedrock: Oreo cookie in the bottom of the cup.
    Bedrock is solid rock. Parent material is formed from the bedrock after a long weathering process. There are two basic ways that weathering can happen: physical and chemical. Physical weathering includes things like wind or water erosion, glacial activity, freezing and thawing, and biotic activity (plant roots, animals, micro-organisms). Chemical weathering includes leaching, oxidation, carbonation, and hydration. 
  • Parent Material: Crumbled cookies as the next layer.
    This is the “C” horizon in a soil profile. It is called the “parent material” because it is the weathered rock and partly weathered soil from which the soil layers above are formed. What influences does the parent material have on the other horizons? (Size of the particles would determine the texture of the soil.)
  • Subsoil: Vanilla pudding as the next layer.
    This is the “B” horizon from the soil profile. It is lighter in color than the layers above it because it has less topsoil and organic matter. 
  • Topsoil: Chocolate pudding as the next layer.
    This is the top layer of soil. Nutrients, bacteria, fungi, and small animals are abundant. Plants thrive in it because of the nutrients. Living creatures (such as worms and insects) are found in this layer.
  • Organic/Litter Material: Coconut and worms on top.
    The coconut represents organic matter. This layer is usually less than an inch thick. Litter decomposes into nutrients that enrich the soil. In areas where the temperature is lower, the composition of organic matter is slower. 

Reflection

  • Repeat the layers of the soil horizon to an adult.
  • What layer do you find living creatures in (including worms)?
  • What layer is also called layer “C”?
  • Do you think soil forms more quickly in Michigan compared to Alaska? Why or why not?
  • Eat your model. What layer was your favorite?

After you have eaten your model, clean up your materials and take care of your supplies.

Other Discovery Kit Activities