Imprints: How Were Dinosaur Tracks Formed?

Problem

How were dinosaur tracks formed?

Materials

• ½ cup (125 ml) flour
• ½ cup (125 ml) cornmeal
• Large mixing bowl
• Spoon
• ½ cup (125 ml) water
• Paper plate
• 8-inch (20 cm) square baking pan with water

Procedure

1. Pour the flour and the cornmeal into a bowl and mix with the spoon.
2. Slowly add the water to the flour and cornmeal; stir until all the water is mixed in. This is your "homemade mud."
3. Pour the "mud" onto the paper plate. Use the spoon to spread the mud evenly over the plate.
4. Wet one of your hands with water from the pan.
5. Spread the fingers of the wet hand and press the palm side of that hand into the mud.
6. Remove your hand. You should see a good print of your hand. If you do not, do it again. Place the plate on a flat surface where it will not be disturbed.
7. Allow the mud to dry. It may take two to five days depending on the temperature and humidity of the air.

Results

The mud dries, leaving a hard print of the shape of your hand.

Why?

The soft, homemade mud moved out of the way as you pressed your hand into it. The same thing happens to soft mud or sand when animals walk or crawl over it. If the imprint made in the soft mud is not disturbed before it dries, a hard print of the animal's track forms. Dinosaur tracks have been found in the Connecticut Valley and other places where these prehistoric animals walked in soft mud or sand. These rare tracks remained because they were covered with layers of dirt and sand and other sediment before the rest of the footprints were destroyed by winds, rains, or the pressure of other animals walking on the dirt. In time the deposit hardened into rock, and the track was trapped forever.

Let's Explore

1. Would the amount of water affect the print? Make different prints by using different amounts of water. Keep a record of the amount of water used with each mud mixture. Photographs of the imprints before and after drying can be used as part of a project display.
2. Would the type of dirt affect the print? Prepare different homemade mud samples by using different amounts of cornmeal and flour. First add more cornmeal and then repeat the experiment adding less cornmeal. Make the thickness of the mud in all samples as alike as possible. Science Fair Hint: Samples of the mud mixtures used can be displayed in small bottles along with photographs of the imprints and the summary stating which samples produced the best imprint.

Show Time!

How can tracks be collected and studied? You can make plaster of paris (available at art supply stores) and pour it into animal tracks that you find in the dirt. Note: Mix plaster in a throw - away container. Do not wash containers in the sink, because the plaster can stop up the drain. Wait about 20 minutes for the plaster to dry. Then carefully lift the plaster from the dirt, and you should have a print. Present your ideas on what animals made the tracks and give your evidence why.

Check It Out!

Discover more about animal tracks and how to identify them. Find a book that shows what tracks are made by which animal.

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Janice VanCleave's Animals
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