Most fossils form this way: A living thing decays and leaves a mold in its own shape behind in the earth. Then rock forms inside the mold, creating a copy of the living thing. This activity will help your child understand how fossils form.
- 4 cups plaster of Paris
- 2 1/2 cups water
- Disposable container
- Old or disposable small baking pan
- Petroleum jelly
- Mix 2 cups of plaster of Paris with 1 1/4 cups of water in a disposable container.
- Spread the plaster in the bottom of an old or disposable small baking pan to a thickness of about 1 inch.
- Wait about 2 minutes until the plaster begins to set.
- Coat your child's hand with petroleum jelly.
- Gently press his hand into the plaster just enough to dent the surface. Hold his hand in place for a few minutes, then remove it and let the plaster set until it's completely hard.
- Coat the hand-shaped mold with petroleum jelly.
- Mix up another batch of plaster and pour it into the mold.
- Let the plaster harden, then gently separate the "fossil" from the mold.
- If they don't separate easily, hold the pan upright and tap it lightly with a hammer.