UCMP Lessons  

Becoming a Fossil

Author: Sharon Janulaw

Overview: In this lesson students make imprints in clay using leaves or shells. They then compare those to how a fossil is formed.

Lesson Concepts:

Grade Span: K–2


Advance Preparation:

— Assemble the materials.
— Prepare a sample impression by pressing two colors of clay together with a leaf in between. Separate the clay layers and discard the leaf.

Time: One class period

Grouping: Pairs

Teacher Background:

Fossils are formed when something dies and instead of being destroyed by scavengers, weather or other forces, it is preserved. The most common form of preservation occurs when a specimen is covered by sediment, which over a long period of time, becomes rock. This most often occurs in lake or bay environments where there is not a great deal of motion in the water. Sediment gently covers the recently deceased organism and covers it with protective layers that later become rock. There are many other ways organisms or their traces can be preserved (as an insect in amber or dinosaurs covered by a landslide or flood) but in this lesson we will emphasize sedimentation.

Teacher Resources:
— The UCMP website has many photos of fossils.
— Real fossils can often be found in “nature” stores or at rock shops.
Dinosaurs Walked Here and Other Stories Fossils Tell by Patricia Lauber

Explore this link for additional information on the topics covered in this lesson:

Teaching Tips:

Emphasize throughout the activity that the class is making impressions of living thing. We can learn from looking at those impressions. This is similar to how we can learn from fossil imprints that we find in ancient sediments. The imprints we are making are not fossils, but they look sort of like real fossils and this helps us to learn.

Vocabulary: imprint, fossil, sediment


  1. Show the class the imprint you made and ask them what they think made the imprint. Ask how they know.
  2. Tell them how you made your imprint and that they will get to make their own imprints.
  3. Distribute two colors of clay to each pair of students and ask them to flatten each piece of clay until it is about 1/2" thick. Have them select a leaf or a shell and press it between the layers of clay.
  4. Tell students to separate their layers of clay and give each pair a chance to share the results with the class. As each pair shares its imprint, have the class guess what the original object looked like for each of the sets of imprints. Ask students how they were able to identify each of the imprints.
  5. Display a number of actual fossils. Ask them to tell what they know about fossils. Ask the class what they think the animals or plants looked like before they were fossilized. Explain that fossils are formed when something dies and then is covered for a very long time without being destroyed.
  6. Explain that the real fossils were not pressed between clay by people, but were formed by natural forces. Tell as much of this story as your students are ready for.
  7. Read Dinosaurs Walked Here by Patricia Lauber and discuss it.
  8. Ask students if they think we made real fossils today. “What makes you think that?” Ask them how their imprints and fossils are different. Use the time line to talk about fossils and how long ago the life forms lived.

Updated May 24, 2004

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