How to Make Effective Models for Sedimentary Rock Formation

modeling sedimentary rock formation

When creating models with students, we really want them to be as accurate as possible. Students are less likely to develop misconceptions and gain a deeper understanding of a complicated process.

This model includes all 5 steps involved in the formation of sedimentary rock: weathering, erosion, deposition, compaction, and cementation.

We like to have students create notes for their interactive notebooks to reference during this lab. Alternatively, you could have them record notes as they progress through the lab.

Materials Needed for Modeling How Sedimentary Rock Formed:

  • cornbread mix (get the just add water kind)
  • food coloring to make 3 colors of cornbread
  • 3-oz disposable cups
  • water in container per group
  • pipette/eyedropper per group
  • butcher paper/tray for mess per group

Optional materials:

  • honey or syrup (to mix into the water)
  • plastic storage baggies
  • additional Three 3 oz cups per group
  • tablespoon for scooping per group

Students will love eating these “sedimentary rocks” when they are finished. If your school or district has restrictions on eating in the classroom, you will need to set expectations with your students.

Okay, here we go.

Colored cornbread

Step 1:

Bake 3 different colors of cornbread. If you plan on crumbling at home, bake in regular pans, however, if you plan on having the students model weathering, bake in mini muffin pans. Plan out about one of each color mini muffin per small group or one tablespoon of crumbled cornbread per person.

modeling the weathering of rock using cornbread

Step 2:

If you are “weathering” yourself, put chunks of the cooked cornbread into a gallon-sized storage bag. Close the bag and then crumble it into small pieces to represent sediment. Count out enough of the mini cups so that each group will have 3 (one filled with each color).

Bottom layer of cornbread to make sedimentary rock model

Step 3:

Use butcher paper or trays to minimize mess. Pass out the cornbread (muffins or filled cups) to each group along with a small container of honey water and a pipette. Give each student an empty 3 oz cup. If you made muffins, have students crumble them into separate cups while discussing how this represents weathered sediments.

second layer of cornbread for modeling sedimentary rock formation

Step 4:

Instruct students to put one tablespoon of cornbread into their cup and gently tap the cup on the table. Then, students should choose a different color of cornbread and add that to the cup.

add sprinkles to model fossils or fossil fuel formation

Step 5:

Add just a few sprinkles or very small candies on top of the second layer. Discuss that these represent organisms that have died and will be buried under layers of sediment.

add 3rd layer of cornbread for sedimentary rock model

Step 6:

Add the last layer of cornbread on top of the sprinkles. This is a great time to discuss what are the possible outcomes of buried organisms (decompose, form fossils, form fossil fuels). Call attention to the amount of space the “sediments” take up in the cup.

add water to model cementation

Step 7:

Use a pipette to add 5-10 drops of honey water to the cornbread. Discuss that this models the mineral-rich water that is present in the layers of sediment and give the example of layers of sediment being deposited in a delta.

press on layers of cornbread to model compaction

Step 8:

Use fingers to press straight down on the cornbread. Students should press firmly to make as compact as possible without damaging the layers or the cup. Discuss that this models the compaction of sediment as layers build up.

side view of compacted cornbread

Step 9:

Tell students that they should try to keep the layers level and not sloped in the cup. Bring attention to the amount of space the “sediments” take up now and discuss how compaction and cementation (honey water) have created new rock.

press bottom of cup to dislodge

Step 10:

Turn the cup over and gently press the bottom until the model falls.

cornbread model of sedimentary rock

Step 11:

Inspect the sedimentary rock model; then, discuss how the layers were formed. Which layer is the oldest and the youngest?

cornbread model of sedimentary rock with a fossil

Step 12:

Break the sedimentary rock model in half. Discuss the sprinkles model. How can we use the layers of rock to determine the age of fossils?

Follow up Activities for How Sedimentary Rock Formed:

While students love all things related to hands on science, it is important to offer them additional practice with the concept of sedimentary rock formation. This will ensure that they have a deep understanding of both the concepts and the supporting vocabulary. Here are some of my favorite activities for reviewing sedimentary rock formation.

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Sedimentary Rock Formation Model with Cornbread

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