Science Fair 2016
Fossils are remains, impressions, or a trace of a living thing, preserved in stone or ice, like shells and bones. Fossils form when an organism (any living thing) dies, and its hard parts are slowly covered with sand, which slowly turns to rock. Most of the time, the original bone or shell dissolves, and only a mold is left. Any new rock that forms will fill in the mold to make a duplicate of the original. This is the process that we will model today.
We need to start with a soft area at the bottom of a lake or ocean for our shell or bone to settle into. We’ll use a cup with a little clay in the bottom to represent the lake or ocean bottom.
We’ll take a shell and press it into the clay (like if a snail died and settled to the bottom of the lake). We’ll remove the shell and leave its impression in the clay.
We’ll need to add some Plaster of Paris into the cup to represent the new rock that forms - in nature, it will take thousands of years to harden and form stone, but our plaster will only take overnight to harden. We’ll have our fossil when we pull everything out of the cup tomorrow.
Activity may be done at home with adult help:
Press a small ball of clay into the bottom of a cup
Press a shell or leaf into the clay to make an imprint
Remove the shell or leaf
Add water into the bag of pre-measured Plaster of Paris
Kneed the powder with the water until it is completely mixed
Add all of the plaster mix into the cup.
Tap cup lightly on the tabletop to remove air bubbles.
Cover the cup and take it home.
Disassemble the cup and clay to reveal the casting left behind.
You may choose to paint their “fossils” once they are completely dry – after a week or so.
Some fossils from my collection
Mako Shark Tooth (Calvert Cliffs, Maryland)
Amonite (West Texas)
Amonite (showing crystal growth) (Madagascar)
Stegodon Tooth (Indonesia)
Clam (New Jersey)
Megelodon tooth (Calvert Cliffs, Maryland)