Lasting Impressions: Making Models

Activity Source: National Park Service

 

Background

Fossils are evidence of organisms that have lived in the past. A fossil can help us understand when and where organisms lived. Scientists can also use fossils to figure out what different environments were like in the past. One type of fossil is known as a mold fossil, which forms when an organism is buried, then decomposes, but the sediment keeps the shape (impression) of the organism. As organisms decompose, they sometimes leave a dark carbon imprint, like in the fossil image on this page. Think about the organisms that live in your area and what their mold fossils might look like.

Materials

  • 1 cup flour
  • ½ cup salt
  • 1 cup cold coffee (or water)
  • 1 cup used coffee grounds (dried)
  • Large bowl or container
  • Spoon
  • Wax paper or foil
  • Leaves, sticks, shells, or other items to make fossils with
  • Paint (optional)

Procedure

  1. Make the “sediment” in which your fossils will be formed:

    a. In a large container, mix 1 cup of flour, ½ cup of salt, and 1 cup dry, used coffee grounds.

    b. Stir in 1 cup of cold coffee.

  2. Set up the “fossils”:

    a. On wax paper, lay out a few leaves, sticks, shells, or other parts of once-living organisms that you think scientists might find fossils of.

    b. Use your sediment mixture to cover each item.

  3. Let the sediment dry. Leaving it in the sunlight can help speed drying.

  4. Once the sediment is dry, flip over the pieces and carefully remove the items to view their imprints.

  5. Optional: Model Carbonization

    a. Study images of fossils that have carbonized.

    b. Use paint on your imprint to model a carbon layer.

Analysis

  1. Exchange fossils with a classmate. Make observations of their fossil, and describe what type of organism you think it is.

  2. Look again at the image on this page. Why might it be darker in some areas?

    a. Scroll through the NPS gallery of fossil images linked in step 5a and make observations.

    b. Which are easier to see details on: dark or light fossils? Why do you think this is?

  3. Look through the list of all National Park System units that have fossils.

    a. Find the park or unit nearest you and visit their website to learn about the types of fossils that have been found there.

    b. Another option is to visit a park known to have many fossils, such as Mammoth Cave (KY), Badlands (SD), John Day Fossil Beds (OR), Florissant Fossil Beds (CO), and Petrified Forest (AZ).

Further Steps

Additional NPS activities on fossils

NGSS Connections

  • SEP: Developing and Using Models
  • DCI: ESS1.C: The History of Planet Earth; LS4.A: Evidence of Common Ancestry and Diversity
  • CCC: Cause and Effect

SDG Connections