Following up on our last discussion about how mountains were made, we talked about fossil distribution using clay to represent the layers of the earth as it gets pushed up in the process of it being made into a mountain. Fossils that were once deep below the earth's surface are now in the mountain. Erosion or other disturbances such as earthquakes can wear down the surface of the mountain, exposing the layers below.
Making models of fossils is not only enjoyable for kids but also helps them to understand how fossils are made. One way fossils are made is by tree sap trapping insects. Amber fossil models are easy and fun to make.
Another type of fossil is called trace fossils. These fossils record the activities of an animal such as a burrow trail or track left behind by an animal. These fossils can give paleontologists information about habitats and living habits of animals. To make a model of these type fossils, take a cup of damp sand and press a pencil into it, leaving a hole or burrow. Next, pour some Plaster of Paris that you have mixed up in roughly a mix of 2 parts Plaster of Paris to 1 part water. Let sit until it has hardened (about an hour or so.) Dump the wet sand into a larger container and have a mini "fossil" dig!
Mold fossil models can also be made with Plaster of Paris. A mold fossil is the indentation or impression left in rock by the remains of a plant or animal. If mineral and rock materials fill the indentation, a cast fossil is formed. We will use the Plaster of Paris to represent the mineral and rock materials. First you have to make the impression. Our impression will be made in clay instead of rock. We used Sculpy, but any clay can be used. Take a shell and press it into the clay firmly and then take it out of the clay, leaving an impression of the shell. If the shell sticks to the clay too much, then wash and dry it off and coat the outside with petroleum jelly. We didn't need petroleum jelly for the Sculpy as it can out cleanly without it. Fill the impression with Plaster of Paris and let sit to harden. Ours hardened in about an hour. Once hard, bend the clay back until the cast pops out of the clay. Ours came out with wonderful detail. The boys enjoyed comparing the original shell to the cast, and came to have an appreciation for the value of fossils.
These fossil model instructions are from How the Earth Works by Michelle O'Brien-Palmer.