Science Sunday - Making Fossils

Crumpet has been talking about fossils a lot lately. When we found this skull last week, he was thrilled to have found his own "fossil".
I decided to show him how a real fossil is made. I found this simple experiment in the book "Backyard Science Experiments" by Q.L. Pearce. We found the book at the thrift store, and it looks like it will be a good resource, especially when Crumpet gets a bit older.
We placed a half inch layer of clay in the bottom of a plastic container, and we smoothed it out. Then we sprayed the clay with cooking spray. Crumpet pressed a seashell into the clay, making a deep impression.
Impression type fossils are called 'trace fossils' or 'cast fossils' and can be footprints, as well as impressions of plants or animals.
Then we made another impression in another container. This time, we mixed up some plaster of paris and poured it over the clay, covering it completely. We let the plaster dry for about half an hour. Then we flipped the container over and released the concoction.
We peeled the clay off of the plaster of paris, and here was the result:
This kind of fossil would have been formed if mud filled in an impression and later dried and hardened. It is called a "mold fossil".
You can use this same process to make molds of footprints found outside, and I think we'll have to try it sometime! Crumpet was very pleased with the results, and now we have even more projects we must save. I spent today checking thrift stores for a cheap bookshelf to house his treasures... They're taking over!!
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