Use this edible sedimentary rock activity to learn about rock formations and layers. Sedimentary rocks are one of the three types of rocks along with igneous and metamorphic. Making edible rock layers is a great way to visualize how the rocks are formed.
Learning about Sedimentary Rocks
Start by showing your child a sedimentary rock. Try to choose one with several visible layers like the one I have here.
Ask your child to look at the rock.
- Why do you think the rock has layers (stripes/different colors)?
- How do you think the rock formed?
Sedimentary rocks are made from sediments – bits of dirt, sand, rocks, shells, bones, etc. – that settle into layers. The older layers are on the bottom. They settled first. With a little bit of pressure and time, the sediments stick together and form the rocks we see.
If you have access to one, show your child a rock core sample. Many university geology departments have rock piles where they toss unwanted rocks. You can usually find a lot of core samples – cylindrical shaped rocks that have been cut from a larger rock. The core samples show the layers of sediment and different rocks very well.
After looking at real rocks, it’s time to visualize the rock formation process by making edible sedimentary rocks. We used layers of rice cereal, chocolate chips, and M&M’s to make our edible rocks. Kids can help with the steps of the recipe under adult supervision. Give your child tasks you know he or she can handle safely.
Recommended Resources for Studying Sedimentary Rocks
Check out some of these excellent resources that you can add to your home or classroom for studying sedimentary rocks.
Possible one of my favourite series of books these DK Eyewitness guides are great and although saying pocket they are full of facts. This rock and minerals version is full of facts and information about different rocks and minerals that you and your children could find.
Ingredients for the Edible Sedimentary Rocks
- 3 Cups rice cereal
- 3 Cups mini marshmallows
- 4 Tablespoons butter
- Pinch of salt
- Splash of vanilla extract
- Mini chocolate chips
- M&M’s, other candies, or more chocolate chips
- Cooking spray or oil to coat the pan
How to Make the Edible Sedimentary Rocks
- Melt the butter in a sauce pan on low heat.
- Remove pan from heat.
- Add mini marshmallows one cup at a time stirring to melt.
- You can add the pan back to the heat as needed to melt the marshmallows.
- Melting the marshmallows slowly will result in a softer treat.
- Once the marshmallows have melted into the butter, add the salt and vanilla.
- Stir in the rice cereal.
- Coat the bottom and sides of an 8″ x 8″ pan with a thin layer of oil. I use a paper towel to wipe out the excess.
- Add half of the rice cereal and marshmallow mixture to the pan.
- Use a rubber spatula to press it down into a flat layer.
- Cover this layer with mini chocolate chips. You’ll want to use more than the picture below. I wanted our chocolate layer to be thicker than we got. (That’s what happens when you let the kids be in charge of adding the chocolate chips.)
- Add another layer of the rice cereal and marshmallow mixture.
- Press down firmly to make sure the layers all stick together.
- Top with M&M’s, other candies, or more chocolate chips.
Allow the edible sedimentary rocks to cool for at least an hour. Cut into squares and serve.
Talk about the layers you see. How many are there? Which layer is the oldest? Which layer is the newest?
More Rock Activities for Kids
- Make sediment jars to learn more about rock layers and dirt.
- Learn about how fossils are made with salt dough dinosaur fossils.
- Read these tips for getting started rock collecting with kids.