Create a Fossil

GRADE LEVEL: 1-4

TIME REQUIRED: One class session

SETTING: Classroom or outdoors

GOAL: The student will create a fossil.

OUTCOMES: At the end of the lesson the student will be able to:

• list three conditions necessary for fossilization,
• state where fossils are usually found, and
• define at least two types of fossils.

KERA GOALS: Meets KERA goals: 1.1, 1.2, 1.3. 2.2, 2.5, 2.6, 5.1, 5.2

BACKGROUND INFORMATION

Fossils are the direct evidence of past life. They are the tools around which geologists and paleontologists reconstruct the history of the earth. They are found in sedimentary rocks. This type of rock is the result of the consolidation of sediment that has accumulated in layers. These depositional environments come from lake bottoms, river bottoms, river sandbars, beaches, and oceans. Some sediments result from weathering rocks, others originate from tissues and bones of plants and animals. It is within the depositional environment that plants and animals may become fossilized. There are three prerequisites that must be met before organic material can be preserved: (1) Organisms must contain hard parts such as bones, teeth, cartilage, or shells. (2) The organic material must be buried quickly in an oxygen-free environment protected from scavengers. (3) Conditions after burial must be favorable as the effects of heat and pressure that produce sedimentary rock may alter the composition and appearance of a potential fossil.

There are several types of fossils. (see pdf version of this lesson for illustrations)

1. Petrification occurs when parts of the organism are saturated with minerals. Highly porous materials such as wood and bone are often petrified.
2. Carbonization occurs when the weight of surrounding sediments squeezes out the water and gas and leaves a residue of carbon (imprint).
3. Molds and casts are replicas of the construction of an organism. A good analogy is Jell-O. The Jell-O is poured into a mold and the finished dish is a cast of that mold.
4. Trace fossils are signs left behind by an organism. Examples include footprints, nests, and burrows.

The rocks of South-central Kentucky began as sediments in a shallow tropical sea. Today, fossils of marine shell life are abundant, and the remains of bryozoans, brachiopods, trilobites, pelecypod (clams), gastropods (snails), and crinoids (sea lilies) are easily found.

A fossil that is always found in the same rock layer is called an index fossil. The index fossil of the Mammoth Cave St. Genevieve limestone is the crinoid. By finding this fossil the paleontologist can date the rock strata.

MATERIALS NEEDED

• Recipe for fossil dough (below)
• Enough dough for each student to make a one-inch ball
• 4” X 4” square of wax paper for each student
• Leaf, shell, or other material from which to make an imprint
• Paint and paint brush

PROCEDURE

1. Provide each student with a square of wax paper.
2. Provide each student with enough dough to make a one-inch ball.
3. On the wax paper, press the dough ball into a disc. The disk should be about the size of a half-dollar.
4. Have each student select a piece of material (shell, bone, leaf, etc.) from which to make an imprint.
5. Press the selected material into the dough. Remove the material, leaving an imprint. Set aside to dry.
6. When dry, may be painted.

EXTENSION

• Discuss the types of materials that are presently being deposited. What can these potential fossils tell future paleontologists about our present day environment?
• Discuss the different types of fossils. Have the students find and/or describe examples of each.

Recipes for Fossil Dough