Special Feature Lesson:

 Fossil Fun

Overview:
Students make models of fossils to further explore characteristics of soil.

Curriculum Focus:
science

Materials:
ï juice or milk carton with top cut off
ï modeling clay
ï Plaster of Paris
ï small item to create fossil, such as shell or toy
ï petroleum jelly

Activity:
Review the More About... story. Discuss the fact that when plants and animals die, their remains are either eaten or else they rot and "disappear" into the soil. Explain that fossils are an exception to this rule. Fossils are the preserved remains of prehistoric plants and animals. These remains (such as bones, teeth, shells and wood) have chemically changed over time to become rocks buried in the earth. Fossils may also be signs of animal activities, such as tracks, trails and nests.

Tell children they are going to make fossil models. Divide children into groups or have them work individually. Allow them to choose an object for their model, such as a shell or a toy. Help them prepare Plaster of Paris according to the package instructions. Share these directions for the activity:

1.  Press a layer of clay into the bottom of the carton. It should be a few inches thick.
2.  Spread petroleum jelly over the surface of your small object.
3.  Press the object into the clay, then lift it out. Be sure the object has left a clear impression in the clay.
4.  Pour enough Plaster of Paris over the clay to fill the impression left by your small object. Let the plaster sit for half
     an hour, to allow it to harden.
5.  Peel away the carton from the plaster and clay layers.
6.  Carefully separate the plaster and clay layers.

Have students look at both the plaster layer and the clay. Explain that fossils can take the form of an impression in rock, like the fossil in the clay, or they can be three-dimensional in form, like the fossil in the plaster. Have students compare their models and observe differences in texture and quality. Discuss reasons why some parts of animals might leave more distinct fossils than others (Flesh, leaves and feathers are much more likely to disappear before becoming fossils than are hardy materials like bone). Consider displaying the fossil models, along with the original objects used to create them. Can students identify which objects left behind which fossils?

Extension idea:
Remind students that fossils show us how dramatically life has changed over time. Prehistoric ancestors of today's plants and animals often looked quite different. Many prehistoric life forms became extinct. Challenge students to put themselves in the shoes of a paleontologist (fossil hunter). Ask them to write about discovering the fossils of an animal that actually lived, or one from their imagination. Tell them to use words and drawings to describe the fossil, the animal it came from and theories about how the animal lived.