Fossils are ancient remnants of once living things. They are our only link to the living past. They tell us of ancient environments and organism habits. Many times they are used to help distinguish periods of geologic time. The absence of fossils in rock can make it difficult to be sure what took place in the past.
Trace fossils are the most common fossils found in nature. They are impressions left in the sediment from once living things. Common trace fossils are footprints or walkways, resting spots, living burrows, feeding burrows, casts and molds. They are not the original parts of an animal. A trace fossil is preserved when mud or dirt that was disturbed by something living hardens and keeps its shape.
There are two main kinds of trace fossils, molds and casts. A mold forms when something is pressed into soft mud and removed by decomposition or pulled out, leaving an impression of the object. A cast is a 3-D example of an object of the past created when a mold fills up with sediment like mud, sand or volcanic ash.
http://www.nps.gov/brca/forteachers/paleoact4.htm
Homemade Geology Dig Kit
I grabbed up some cool rocks, gems, & fossils and made him a “dig block,” he can enjoy. It’s really simple and inexpensive. I already had plaster of Paris & sand laying around.
Materials for Dig Block:
Plaster of Paris / Throwaway Container for mixing / Mixing stick
Sand
Cinnamon
Shoebox Sized Container or foil pan as a mold
Objects to ‘hide’ in the block
Making the Dig Block:
For the mold, I used a small foil loaf pan. It worked great. At the end, the block slid right out of it.
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