How Fossils Form Activities
A common classroom activity for demonstrating how fossils form is to make a mold in plaster and then a cast in plaster from the mold. We include here a list of several websites where you can find plaster molds and casts activities, as well as the same exercise using white glue and candle wax in case you don't want to mess around with plaster. There are also activities for demonstrating how petrification and carbonization work, as well as for understanding fossil trackways.
White-glue fossils: Casts, molds, and impressions
You don't want to mess with plaster to make fossil molds? Here's a simple solution. Students make impressions and molds in clay and then make casts with glue. After the glue dries, students pull back their “fossils.”
Candle-wax fossils: Casts, molds, and impressions
Students make impressions and molds in clay and then, with the help of their teacher, make casts with candle wax. After the wax dries, students pull back their “fossils.
Impressions in clay
To illustrate how impressions form, and how hard or easy it is for organisms to leave impressions, students will make impressions of different objects in clay.
Leaf Impressions (a model for carbonization)
To illustrate how carbonization works, students will make leaf impressions on paper.
Many fossils are preserved through the process of petrification (also called mineralization). Petrification occurs when water carries minerals into the pore structures of parts of buried organisms, leaving the minerals behind. When the original organic material ultimately rots or dissolves, the minerals remain in the position of the original structures. Wood and bone are commonly fossilized in this manner. You can demonstrate how this happens by using the old capillary action demonstration; a piece of celery and dyed water. The colored water is our model for mineral-laden groundwater. When the dyed water is naturally sucked into the celery by capillary action, it mimics groundwater moving into the pore spaces of bones and plants, leaving minerals behind in the pore spaces as happens in petrification.
Fossils are evidence of ancient life (usually) preserved in stone. When most people think about fossils, they think about bones and skeletons. Not all fossils, however, are the body parts of ancient organisms. A very important type of fossil is called a trace fossil (scientifically termed an “ichnofossil”). Trace fossils are the tracks or trails an organism leaves behind. In this activity, students will make trackways by running across sheets of paper, and then their classmates will determine what they can interpret from the trackways.