Students will be able to:

• Describe what animals and plants left behind to make fossils.
• Create a "fossil" impression or mold.
• Examine fossils and casts and identify characteristics of various fossils.
• Define the following words: fossil, paleontologist, cast, and mold.

Associated Standard and CORE Objective:

• 3040-0405 - Collect and analyze data about Utah fossils and infer how fossils are formed. Record observable features of fossils. Make inferences about origin of fossils. Predict where fossils might be found, based on inferences. Construct a model of a fossil.
  
  

•    - Worksheet Master "Can You Find the Fossils?"
•    - Bryozoan and Brachiopod Data Sheet
• 6 - Fossil display boards
• 1 - Bird with feathers cast, in box
• 1 - Edmontosaurus foot cast
• 4 - Bryozoan and Brachiopod containers
• 1 - Wood Round (cross section of tree trunk)
• 1 - Pink rubber footprint mold
• 1 - Photo of a paleontologist
• 1 - Photo of workers digging fossils at a field site
• 1 - Edmontosaurus Poster
•    - Bags of casting plaster (5½ cups per 2 cups water)
• 1 - Measuring cup
•    - Balls of clay in cups
•    - Shells
• 1 - Tarp
  
  

• Bring the children together into a semicircle around the table on which you will be making the cast.
• Ask the children what normally happens when a living thing, or organism, dies. Usually scavengers eat the flesh, and bacteria decompose the rest. After the flesh is stripped off, the exposed bones are broken down by processes such as crushing, chewing, freezing, and thawing.
• Explain that once in a while parts or traces of an organism are preserved or "fossilized." To become fossilized, an organism must be quickly buried in order to protect it from bacteria and oxygen that would destroy it. Ask the children what the word fossil means. The word fossil means "something dug up." A fossil is a remain or trace of an organism from the ancient past, usually preserved in rock.
• Ask the children what kinds of fossils they have seen. Explain that fossils are not only actual bones and teeth but also imprints of leaves, footprints, tracks, and burrows. Ask the students where we go to find fossils. Fossils are found in mountains, swamps, and other places.
• Ask the children what kinds of people look for fossils. Show the photo of Jack Horner, a Montana paleontologist. Explain that paleontologists are scientists who study fossils in order to study ancient life. Show the photo of the workers digging fossils at a field site.
• Tell the children that they will be paleontologists for the day and study different ways that fossils are made and replicated.
  
  

• With the children still in a semicircle, show them the dinosaur footprint cast. Ask what they think it is. Explain that it is a dinosaur footprint that was found on the roof of a Utah coal mine. Ask the students how they think the footprint was formed. Ask the students what happens when they run across a muddy field after a rainstorm. Their feet press down and leave impressions in the wet mud, which later dries. Explain that that is one way a fossil is created. A natural cast, similar to this manufactured cast, is made by sand or mud filling into a dried depression of a footprint of a dinosaur.
• Tell the children that another kind of fossil is a mold. For example, a fish dies, falls to the bottom of a lake, and mud fills in around the fish. Later, the fish body dissolves and leaves a hollow depression called a mold. If the mold fills in with minerals or mud, the fill-in material is a cast. Show the students the pink rubber mold. Tell the children that this is an artificial mold of a dinosaur foot. Explain how paleontologists often make artificial molds and casts of fossils using rubber or plaster. Describe how they can then display, study, or sell the cast and molds. Tell the children that you are going to create a cast right now using the mold.
• Spread the cover over the table. Place the foot mold on top of the tarp. Pour 2 cups water into zip lock bag of 4 cups of plaster powder (2:1 ratio) and knead until smooth, lump-free consistency is produced. Snip off one bottom corner of bag with scissors and squeeze plaster mix into pink mold in cake decorator fashion. Gently tap the mold to remove air bubbles. After 20 minutes or when the plaster has partially set, use a pointed instrument to etch in the name of the students' teacher and the date into the plaster cast. After 30 minutes, when the cast is hard (at the end of class), separate the sides of the mold from the plaster. Carefully remove the cast, starting from the "heel" of the plaster foot. Let the children put their hands over the top of the plaster foot and feel the heat of the chemical reaction. (If the plaster is not hard enough to take out at the end of class, show the students the foot and take their plaster foot out after class.) Once the foot has been removed, allow it to dry for at least a day. Once completely dried, the mold can be finished with acrylic paint. Throw away the bag and do not pour the excess plaster down the sink.
  
  

(Demonstrate the procedure before passing out the clay and shells.).

• Divide the students into pairs.
• Pass out one shell and a piece of modeling clay about the size of a student's fist to each pair of students.
• At their desks, have each pair of students divide the clay into two equal parts. Each student gets one half.
• Have one student press one half of the clay flat and smooth. Then have the student press the shell gently into the clay, leaving part of the shell sticking out of the clay.
• Have the second student press out the other half of the clay and put it over the shell in the first half of clay. Have the student carefully press the two pieces of clay together.
• Have one of the students carefully separate the pieces of clay and remove the object. The print of the object should be seen on both pieces of clay. Review how fossils can be impressions left in the rock after the original object has left or decayed away.
• Have the students return the fossils to the box and the clay to its containers.
  
  

Bring the children back into a semicircle. Using the attached "Teacher Guide to Fossils" sheet, read the short description to the students as you identify each fossil. Note that numbers on the teacher's guide match the numbers painted on the fossils.

Next, set the fossils stations up so the children can walk around the room and look at the fossils. Make sure that the Edmontosaurus foot (#17), toe cast (#18), and poster are placed where they will not be tipped over. The petrified wood (#12 and #13) should have the wood rounds next to them for comparison.

1. Display the brachiopod/bryozoan data sheet with the rocks and discuss it with your students.
2. Have students identify the fossils as either bryozoan or brachiopod.
3. Then have them examine them closely on all sides of the rock with the attached hand lens.
4. Have them discuss what type of environment these fossils lived in.
   
   

Career Fields:

Science

Occupations:

• Geologist: Study the physical aspects and history of the earth. They identify and examine rocks, study information collected by remote sensing instruments in satellites, conduct geological surveys, construct maps, and use instruments to measure the earth's gravity and magnetic field. They analyze information collected through seismic studies. Education: Bachelor's Degree

• Paleontologist: Study fossils found in geologic formations to trace the evolution of plant and animal life and the geologic history of the earth. Education: Bachelor's Degree
  
  

1. What is a paleontologist?
2. What is a fossil? How are they formed?
3. What do fossils tell us? What do they reveal about the past?