Rock/Fossil Layer Simulation

6th Grade Science, Unit 4: “Plate Tectonics and Fossils”

Fossils

GOAL: Students make a model of rock layers and fossils to see how rocks and fossils are used to understand the age and geological history of the Earth.

Big Ideas: The Earth has distinct layers of rock which show progression of organisms from layer to layer. Newer rock layers are on top. Observing the layers in which fossils are found allows scientists to estimate the order of prehistoric and geological events.

GLCE Alignment:

E.ST.06.31Explain how rocks and fossils are used to understand the age and geological

history of the Earth (timelines and relative dating, rock layers).

S.IP.06.11 Generate scientific questions based on observations, investigations, and

research about the plate tectonic movement.

S.IA.06.12 Evaluate data, claims, and personal knowledge through collaborative science

discourse about the theory of tectonic plates and the importance of evidence

through fossils.

S.IA.06.13 Communicate and defend findings of observations and investigations into

major geological events and earth processes using evidence.

S.RS.06.11 Evaluate the strengths and weaknesses of claims, arguments, and data

regarding plate tectonics and the evidence provided by fossils.

S.RS.06.12 Describe limitations in personal and scientific knowledge regarding plate

tectonics and the history of the Earth.

S.RS.06.14 Evaluate scientific explanations based on current evidence and plate

tectonics and evidence from fossils.

BACKGROUND

Prior Knowledge: Fossils provide evidence of the existence of an organism from the past, such as the skeleton of a dinosaur, or the imprint of an extinct plant. Fossils are remnants of an organism preserved in the Earth's crust. Fossils include tracks that have filled with sediment and turned to rock, burrows, andpreserved feces.

Common Misconception: Fossils are only bones or imprints found in rocks.

Timeframe of Activity: 1-2 50-minute class periods

VOCABULARY:

fossils

geological history

rock layers

MATERIALS:

For each group of 3-4:

3 different colors of aquarium gravel – ¼ cup each color

3 sandwich size plastic bags

¾ cupsand

¾ cupsoil

¼ cup measuring cup

plastic spoon

clear container (possibly a 2L soda bottle with top cut off – or equivalent)

small plastic animals and plants (about 6)

water (enough to fill each clear container halfway)

For each student:

1 Student Reading Sheet “Fossils”

1 Student Question Sheet “Fossils”

1 Student Analysis Question Sheet

PROCEDURE:

Advance Preparation for Teacher: Set up 3 baggies for each group, each baggie has ¼ cup of different colored aquarium gravel.

  1. Introduce activity by reviewing prior knowledge and vocabulary. Explain to students that they will be modeling the formation of rock layers over time. This also provides a good opportunity to discuss the advantages and disadvantages of using models in science.
  2. Distribute materials to each group.
  3. Students measure and add ¼ cup sand and ¼ cup soil to each baggie of aquarium gravel.
  4. Add one or two of the small plastic plants or animals to be fossil models.
  5. Shake the gravel/soil mixtures to thoroughly mix the materials.
  6. Fill the clear container ½ full with water.
  7. Use a spoon to slowly sprinkle the gravel/soil mixture from one of the baggies into the water.
  8. Wait 10 minutes and observe. (During the 10 minutes, students can begin the “Fossils” reading and questions sheet.)
  9. Explain that each 10 minutes represents thousands to millions of years.
  10. Repeat the process with the 2 remaining baggies every 10 minutes.
  11. When the model is complete, sketch the rock layers and label oldest to newest – as shown in Figure 1 from the reading.
  12. Complete the Analysis Questions.
  13. Finish the “Fossils” reading and question assignment and discuss.

**Student sheets and answer keys on the following pages* *

Name ______

Analysis Questions – Rock Layer Fossils Model

  1. What did the aquarium rocks, sand, and soil mixture represent in your model?
  1. What did the plastic plants and animals represent in your model?
  1. What were the strengths and weakness of the rock layer and fossils model?

(Hint: Think about ways in which the model did or did not represent real rock

layersand fossils.)

  1. Which color of the aquarium gravel mixture represents the oldest layer of rock in your model?
  1. Which color of the aquarium gravel mixture represents the newest layer of rock in your model?
  1. Did any of your rock layers have the same “fossils” in them? Explain why or why not that would be an accurate representation of real rock layers.

Name ______KEY______

Analysis Questions – Rock Layer & Fossils Model

  1. What did the aquarium rocks, sand, and soil mixture represent in your model?

Layer of rock

  1. What did the plastic plants and animals represent in your model?

Fossils

  1. What were the strengths and weakness of the rock layer and fossils model?

(Hint: Think about ways in which the model did or did not represent real rock

layers and fossils.)

Student responses may vary.

Strengths Examples:

Rock layers were oldest on bottom and newest on top.

Fossils were found in each layer.

Weaknesses Examples:

Each rock layer was made of the same materials.

Some layers had the same fossil types.

  1. Which color of the aquarium gravel mixture represents the oldest layer of rock in your model?

Will be different for each group depending on how they chose to do it – must be the color in the bottom of their container.

  1. Which color of the aquarium gravel mixture represents the newest layer of rock in your model?

Will be different for each group depending on how they chose to do it – must be the color on top of their container.

  1. Did any of your rock layers have the same “fossils” in them? Explain why or why not that would be an accurate representation of real rock layers.

Having the same fossils in every layer would not be an accurate model because real rock layers show that different organisms lived during different time periods.

Name ______

Fossils

The term fossil comes from the Latin term for “dug up.” Fossils are evidence from organisms that once lived on Earth. Examples of fossils include bones, teeth, shells, imprints of leaves, and footprints. Fossils can also be entirely preserved organisms, such as a mosquito preserved in amber, a mammoth frozen for thousands of years in a Siberian field, or a saber-tooth tiger preserved in the LaBrea tar pits. Fossils can form in a variety of ways and provide paleontologists (scientists who study fossils) with a glimpse of the organisms that once lived in a certain area. Paleontologists can use this information to infer how the environmental conditions and life have changed over time.

Formation of Fossils

Most fossils are found in sedimentary rock, which are the most common rocks on Earth’s surface. Sedimentary rocks form when particles of existing rock (sediment) settle in layers, typically in the bottom of lakes, rivers, and oceans. The sediment becomes compacted and cemented together over a long period of time. Fossils can form in a variety of ways. Fossil formation usually occurs when organisms experience rapid burial, such as an underwater land slide or being covered by volcanic ash. When organisms get trapped in the layers of sediment, they have the possibility of becoming fossilized. The soft structures such as skin, internal organs, and muscles are rarely preserved in fossils because these soft body partsusually decompose before they can be preserved. However, it is possible for small particles of rock to surround an organism and preserve an imprint of its shape, including its soft tissue. Typically, only the hard structures of plants and animals will fossilize. In some cases, the hard body structures are replaced with minerals that preserve the remains of the organism. Not all organisms die under conditions where their bodies will become fossilized. Since fossilization is a relatively rare event, fossils can be difficult to find and dig up. The fossil record provides information to scientists about how organisms have changed over time.

Fossils Providing Evidence of Past Life

The study of fossils can provide vast amounts of evidence to show how life and environmental conditions on Earth have changed over time. The layers of sedimentary rock represent layers of the Earth’s history. In an undisturbed portion of rock, the newer rock layers form above the existing layer of rock, so the older layers would be closer to the bottom of the sample and the newer layers would be closer to the top. Scientists use this to relatively date rock layers and the fossils within them.The layers within sedimentary rock also represent a timeline. The information contained in the fossil record allows scientists to conclude that environmental conditions on Earth have changed throughout its history. Fossil evidence suggests that the organisms on Earth have varied greatly over its long history. The fossil record serves as a vast database that documents past life that has existed on Earth. Fossils also provide evidence for major events in Earth’s history such as the extinction of the dinosaurs and the evolution of land plants. The information from the fossil record can be organized into a timeline showing time periods of great biodiversity. This timeline is known as the geologic time scale, which divides major events of the Earth’s history.

Dating Fossils
Scientists can estimate the age of fossils by comparing them to the age of other fossils. This technique is known as relative dating, which combines the use of index fossils and the principle of superposition (older rock layers are deeper in the Earth than more newly formed layers). Index fossils are fossils of organisms that existed in large quantities, for a relatively short period of time in Earth’s history, and were geographically widely distributed. Relative dating is useful, but it only gives scientists an approximate age of a specimen compared to the age of another fossil.

(Source:

Name ______

Fossils Questions

  1. What are fossils?
  1. Give (3) examples of fossils.
  1. Where are most fossils found?
  1. How are fossils formed?
  1. What type of information do fossils provide to scientists?
  1. How can scientists tell which rock layers and fossils are oldest?
  1. How do scientists estimate the age of fossils?

Use Figure 1 to answer the following questions.

  1. Describe the organisms found in the oldest rock layer.
  1. Were fish or plants living first? Explain how you can tell.
  1. Describe the organisms found in the newest rock layer.
  1. Describe the organism that was living at the same time as fish.

Figure 1 – Rock Layers with Fossils

(Image Source: