Lesson Plan

Clay Fossils

Florissant Fossil Beds National Monument

Grade Level:: Upper Elementary: Third Grade through Fifth Grade
Subject:: Science
Lesson Duration:: 60 Minutes
State Standards:: Colorado Academic Standards for Science
3rd Grade
o LS4-A-1
4th Grade
o LS1-1, ESS1-1
5th Grade
o ESS2-1, PS1-1

Essential Question

What are some of the many ways ancient life can be preserved as a fossil?

Objective

During fossilization, certain characteristics of an ancient organism can become preserved. Students will learn about compression, impression, mold and cast fossils and how they are formed. Students will then create fossil replicas that imitate fossilization processes that are common in the Florissant Fossil Beds area.

Background

Fossilization is the preservation of ancient life. Any indication, or clue, that an organism lived and interacted with its environment can be an example of a fossil. Unique conditions must be met in order for an organism to become fossilized. In fact, it is estimated that less than 1% of all life that has ever existed on Earth has been recorded as a fossil! Common examples of fossilization include molds and casts, permineralization and replacement, compression and impression, and trace fossils.

Molds and casts

Mold is a deep impression of an organism, but the actual organism has decayed away with time.
Molds can get filled in with minerals or other sediments to form a cast.

Permineralization & replacement

Permineralized fossils occur when minerals dissolved in water seep into an organism’s empty spaces and crystalize in place. Florissant’s petrified wood is permineralized
Replaced fossils are similar to molds and casts—where an organism’s original shape is preserved but the organism itself slowly rots away. The organism is replaced entirely with minerals, preserving the original shape.

Compression & impressions

Compression fossils – a fossil that has been physically crushed in between fine layers of sediment such as clay and even volcanic ash. These form in environments where fine sediment can get deposited, such as along rivers lakes, and ponds. This type of fossilization is common with plants since leaves are basically flat and result in minimal distortion when compressed. Whereas, this type of fossilization is uncommon for animals, and with 3-dimensional shapes only the basic outline and surface features are preserved.
Impression fossils – when a plant or animal decays away entirely, only leaving behind an imprint or impression of itself.
Many of the fossils described by scientists at Florissant Fossil Beds, are carbon compression and impression fossils that formed at the bottom of the ancient lake. Lakes can be still, so things can easily settle to the lake bottom to get covered up by sediments to eventually become compacted into fine and thin layers of clay and volcanic ash. In ancient Florissant, the still lake also collected leaves, insects, plant debris and even small animals that were then buried in layers of clay and ash.

Trace fossils

Trace fossils show the evidence that an organism was present, but its body was not fossilized. They are also known as ichnofossils and include footprints, bite marks, feces, vomit, and burrowing. Trace fossils may tell us about organisms that themselves did not become fossils. They can also tell us about an organism’s diet, movement pattern, tooth type, or feeding behavior.

Preparation

Air dry modeling clay
Insect figurines
Leaf & flower stamps
Wooden handled FLFO stamps
Non-toxic ink pads and refill ink
Alcohol wipes
Foam cut-outs of insects and leaves
Paper
Images of FLFO shale fossils and classic examples of other types of fossils

Lesson Hook/Preview

Fossils are the preserved remains of ancient life. By studying fossils, we can learn about ancient organisms, what they looked like, where they lived, and even how our planet has changed through time. Everything lives and dies, but not everything gets turned into a fossil. Specific conditions are required to preserve an organism as a fossils. By studying different forms of fossilization, we can get a better understanding of what ancient organisms looked like. By mimicking these different forms of fossilization, such as compression and impression, we can have a better idea of how the fossils formed.

Procedure

Give a brief lesson to students regarding the types of fossilization and the purpose of this demonstration. Include a gentle warning to students that the demonstration can be messy, so to try and keep the ink off their clothing and desk surfaces. Keep the alcohol wipes close and open!
Ask for a few (no more than 5) volunteers to help with a messy demonstration of how carbon impression fossils formed in the bottom of ancient Lake Florissant.

Demonstrate the Hand Shale activity with 5 volunteers. Have students stand where the class can see them. Tell the story of how the volcano erupted and deposited ash into the lake making layers. Students will stand in a circle and alternate putting a hand into the bottom of the lake to represent ash. On top of each hand place a foam shape with ink on both sides. Students will use both hands, and as they stack on top of each other they will collect foam fossils within most layers. Continue the story as the lake eventually fills in with volcanic material and the layers of their hands compress. Then scientists eventually find the layers and peel them apart revealing the part/counterpart of carbon compression fossils! Have students show the class their hands and then they can wash.

If the class wants to make their own hand shale, separate them into 5 groups. Have the original volunteers help each group as the storyteller who will help the group repeat the demonstration. Have students study some of the details of their fossils, including the two parts, the quality, and if they are identifiable. Remind them not to touch anything!
Once the students are cleaned up and seated, discuss question #1.
Discuss question #2 and then explain the answer. Ask what we would need to make an impression fossil and have them record their ideas.
Discuss with the students Question #3 and question #4.

Let students know that they will now be making an impression fossil replica to take home! They will need time to dry so it will be best if they are left at school for a few days.
Separate students into small groups so they can share art supplies. Give each student a piece of paper.
Each student will get ½ a packet of air dry clay—approximately ½ oz each. Have students shape their clay into 2 small balls. Then flatten the balls of clay onto the paper.
While students are rolling and flattening their clay, give each group an ink pad, some plastic insects, and some leaf and flower stamps.
Use the leaf or flower stamps to stamp down onto the clay. This is your impression fossil. Set aside to dry.
Repeat the process for the second ball of clay but dip the stamp or insect into ink first. This is a carbon impression fossil. Set aside to dry.
Have students clean their hands and workspaces and then discuss question #5.

Vocabulary

Fossil
Molds & Casts
Permineralization & Replacement
Compression & Impression
Trace fossils
- Ichnofossils
Fossil record

Assessment Materials

Clay Fossils Assessment

Describe what your hand shale fossils looked like. Were any of the fossil replicas on your hands distorted?
Was the hand shale demonstration an example of a compression or an impression fossil?
Why is plant material more likely to become a carbon compression fossil?
What would be the perfect conditions to make excellent quality fossils? You can answer this about ancient Lake Florissant or about the hand shale demonstration.
How do our clay replica fossils demonstrate how impression fossils are formed?

Rubric/Answer Key