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Science - 4th Grade
Standard 4 Objective 1
1 class periods of 60 minutes each
Plaster of paris is used to demonstrate two ways fossils are formed.
For each group of 2-4 students:
Fossils are evidence of living organisms from the past and are usually preserved in sedimentary rocks. A fossil may be an impression left in sediments, the preserved remains of an organism, or a trace mark showing that an organism once existed. Fossils are usually made from the hard parts of an organism because soft parts decay quickly. Fossils provide clues to Earth's history. They provide evidence that can be used to make inferences about past environments. Fossils can be compared to one another, to living organisms, and to organisms that lived long ago.
Permineralization is a fossilizing process in which hard substances of animals, such as bone, teeth, or shell are buried in sediment. Groundwater seeps into the sediment. Minerals in the groundwater replace minerals in the hard animal parts or are deposited in the pore spaces of the organism. This replacement of organic materials hardens the animal part and preserves it as stone. This process takes a very, very long time. In this demonstration, the students will be able to see how minerals can displace air in a sponge and make it harder. The sponge represents the animal material, the plaster and water are much like the actual mineral- laden water that would fossilize a bone. This demonstration will work much faster than natural processes.
Some fossils are molds of tracks and trails made by animals as they walked through soft mud or sediment. The mud or sediment later turned to stone, thus preserving the tracks or trails.
Use the rubric below to access their science journal entry.