Fossils and Carbon Dating Created for SPICE by Rachel Naumann and Melissa Henkel May 2008 Lesson 1: Fossil Detectives

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1 Fossils and Carbon Dating Created for SPICE by Rachel Naumann and Melissa Henkel May 2008 Lesson 1: Fossil Detectives KEY QUESTION(S): What is relative dating and how is it used? SCIENCE SUBJECT: Earth/Space Science GRADE LEVEL: 6 th -8 th SCIENCE CONCEPTS: Relative dating of fossils OVERALL TIME ESTIMATE: One 50 minute period. LEARNING STYLES: Visual, auditory, and kinesthetic. VOCABULARY: Relative Dating Principle of Superposition Relative Age LESSON SUMMARY: In this lesson, students will take core samples containing three different types of fossils. The cores will contain three layers, each differing in the types of fossils they contain. Using the Principle of Superposition, students will put the fossils in chronological order and see how scientists use the technique of relative dating to date fossils. STUDENT LEARNING OBJECTIVES: The student will be able to Define relative dating 2. Identify oldest and youngest layers in a vertical rock sample with horizontal layers. 3. Place fossils in chronological order based upon their location in rock layers. MATERIALS: Per Class: 1. Area large enough to disperse fossil confetti. 2. Tape to mark floor grid

2 3. 7 copies of each fossil sheet - Euomphalus Fossil Sheet, Illaenus Fossil Sheet, and Rhipidomella Fossil Sheet Per 3-4 students: 1. 3 paper or cardboard circles 2. 3 envelopes labeled Fossil Detectives Worksheet BACKGROUND INFORMATION: Typically, when one hears the word paleontology, the first thing that comes to mind is the study of dinosaurs. While the study of dinosaurs generally gains the most focus in this field, paleontology encompasses the entire realm of prehistoric organisms to gain information about the past. By studying fossils, or the preserved remains of once living organisms, scientists are able to piece together a geological timeline. One common technique scientists to date fossils is a method known as Relative Dating. This technique is based on the Principle of Superposition, which states that in areas of horizontal rock that are undisturbed, the bottom layer is the oldest while the top layer is the youngest. Therefore, a fossil found in the bottom later is presumed to be older than a fossil found in the middle or top layer. By comparing the fossils found in different rock layers to one another, scientists are able to determine its Relative Age, or its age in comparison to another fossil. In addition, scientists may correlate fossils around the world to date a particular layer of the Earth. Though this technique does not provide a specific age for a fossil, it allows scientists to construct a relative geological timeline. ADVANCE PREPARATION: 1. Mark off a 4 by 4 grid in the room with tape in 1 square blocks. 2. Cut out the fossils from the copies of each fossil sheet and make a pile for each fossil. 3. Divide the fossils into the three envelopes for each group in the following distribution. The exact number of each fossil in each packet is not important, just the type of fossils the packet contains. a. Packet 1: Illaenus b. Packet 2:Illaenus and Rhipidomella c. Packet 3: Euomphalus and Rhipidomella

3 PROCEDURE 1. Divide the students into groups of Give each group 3 cardboard or paper circles and PACKETS 3. Have one member from each group place one of their three circles anywhere on the grid. The only constraint is that they cannot place it on another groups circle. 4. Once each group has placed their circle on the grid, have one member from each group take turn sprinkling the fossils from Packet 1 anywhere within the grid. Some cores will have fossils and some may not. 5. Have the second member from each group place the second circle directly on top of their group s first circle. 6. A member from each group should sprinkle the fossils from Packet The third member should place the remaining circle on their existing core. 8. A member from each group should sprinkle the fossils from Packet The students need to CAREFULLY collect their core sample, making sure not to spill any fossils from the top layer, and place the core on their lab station. Discussion Questions: These questions are included in the lab worksheet, but may be discussed as a class wrap up at the conclusion of the lab. 1. Which layer in your core was the youngest? How do you know this? 2. Which layer in your core was the oldest? How do you know this? 3. List the fossils A, B, and C in order from when they first appeared on Earth. Why did you put them in that order? 4. What problems could scientists face when using relative dating to date fossils? ASSESSMENT SUGGESTIONS: 1. Have student define relative dating on a test. 2. In a lab situation, give the student a rock sample with layers, and have them identify the oldest and youngest layers. 3. Using a diagram of rock layers containing fossils, have the students put them in chronological order. EXTENSIONS: ACTIVITIES: Students may perform a geological dig. Prepare a fossil rock with different colored layers from plaster of paris containing 3-4 fossils. Have the students excavate the fossil rock and put the fossils in chronological order.

4 REFERENCES: Devonian and Silurian Fossils. Maryland Fossils. April Maryland Geological Survey. < Gastropods. Prehistoric Life. Victoria Museum. April 2008 <

5 Name(s) Date Fossil Detectives Today you are going to be a paleontologist! You have found several different fossils, but you do not know in what order they appeared. One technique scientists use in order to date fossils is known as relative dating. When scientists use relative dating, the age of a fossil is its age compared to other fossils. In this lab, you will take a sediment core that may or may not contain the different fossils. By looking at the different layers in your core, you will be able to determine the order in which the fossils appeared. Directions Follow the directions your teacher gives you in order to obtain your sediment core. Questions Look at the top layer in your core. Circle the fossils you had in your top layer. How many of each did you have? A B C Remove the top layer in order to view the middle layer. Circle the fossils you had in your middle layer. How many of each did you have?

6 A B C Remove the middle layer to view your bottom layer. Circle the fossils you had in your bottom layer. How many of each did you have? A B C How many of each fossil did you have TOTAL? A B C

7 Discussion 1. Which layer in your core was the youngest? How do you know this? 2. Which layer in your core was the oldest? How do you know this? 3. List the fossils A, B, and C in order from when they first appeared on Earth. Why did you put them in that order? 4. What problems could scientists face when using relative dating to date fossils?

8 Euomphalus Fossil Sheet

9 Illaenus Fossil Sheet

10 Rhipdomella Fossil Sheet

11 Fossils and Carbon Dating Created for SPICE by Rachel Naumann and Melissa Henkel May 2008 Lesson 2: The Fall of Frosty KEY QUESTION(S): How do scientists determine the exact age of a fossil? SCIENCE SUBJECT: Earth/Space Science GRADE LEVEL: 6 th -8 th SCIENCE CONCEPTS: Absolute Dating of Fossils OVERALL TIME ESTIMATE: One 50 minute period LEARNING STYLES: Visual, auditory, and kinesthetic. VOCABULARY: Absolute Age Relative Dating Radioactive Decay Half-Life Radiometric Dating LESSON SUMMARY: In this lesson, students are asked to help the local police department determine the exact time Frosty the Snowman was taken out of the freezer. By determining the rate at which ice melts over a ten minute period, they are able to back calculate the time the ice was put out. This activity serves as an analogy for carbon dating, demonstrating how scientists collect data in the present in order to extrapolate information from the past. STUDENT LEARNING OBJECTIVES: The student will be able to Define the term absolute dating. 2. Describe how the rate at which ice melts relates to absolute dating techniques. MATERIALS:

12 Per group of 3-4 students 1. Funnel (transparencies may be used as substitutes) ml Graduated Cylinder 3. Ice 4. Stopwatch 5. Calculator 6. The Fall of Frosty Worksheet BACKGROUND INFORMATION: Typically, when one hears the word paleontology, the first thing that comes to mind is the study of dinosaurs. While the study of dinosaurs generally gains the most focus in this field, paleontology encompasses the entire realm of prehistoric organisms to gain information about the past. By studying fossils, or the preserved remains of once living organisms, scientists are able to piece together a geological timeline. One technique scientists use to date fossils is known as Absolute Dating. Unlike Relative Dating, which provides a fossil s age by comparing it to other fossils, absolute dating provides an absolute age. Scientists are able to determine this by using the atomic properties of the materials that comprise the fossil. Atoms are made of three particles: the neutron and positively charged proton found in the nucleus, and the negatively charged electron cloud that surrounds the nucleus. The property of an element is determined by the number of protons it contains. For example, any element with 6 protons is a carbon atom. However, if the number of neutrons differs, a different form, or isotope, of the element exists. Atomic isotopes can be unstable. It that is the case, they will undergo a process called Radioactive Decay, in which they break down into more stable isotopes or particles. The time it takes for half of the parent isotope to undergo radioactive decay to the daughter product is known as the isotopes Half-life. Because the half-life of an isotope is constant, scientists can measure the ratio of the parent to daughter ratio to back calculate the age of a fossil. This process is known as Radiometric Dating. A common example of radiometric dating is Carbon 14 dating. While a well known technique, carbon 14 dating can only be used to date fossils that were once alive. When an organism is alive, the ratio of C-14 to C-12 remains constant due to the carbon cycle. Once the organism dies, the ratio of C-14 to C-12 begins to decrease as the C-14 begins to decay. In addition to C-

13 14, there are other radioactive atoms, such as K-40/Ar-40, that may be used for radiometric dating. ADVANCE PREPARATION: Before the laboratory begins, set up a funnel and graduated cylinder at each lab station. Fill each funnel with ice minutes before the lab begins to allow the ice to partially melt into the graduated cylinder. If more than one class period is performing the lab, you can continue to fill the funnels with ice. If the water level rises above 15 ml before the next class arrives, empty the graduated cylinders between classes. PROCEDURE 1. Introduce the lab to the class by telling them Frosty the Snowman was going to visit, but since he is made of snow and ice, he can only be out of the freezer for a short period of time. Unfortunately, someone took him out took soon, and he is now melting at the lab stations. The local police department has asked for their help in solving this mystery. In order to discover who committed this offense, they need to determine at what time Frosty was taken out of the Freezer. Students may ask how this relates to fossils. Let them know it is an analogy to carbon dating, and it will become clear at the end of the lab how the activity relates to the dating of fossils. 2. Divide the class into groups of 3-4 students 3. Once at lab stations, have each group record the time and the initial volume of water in the graduate cylinder. 4. Start the stop watch. 5. Record the volume of water in the graduated cylinder every minute for ten minutes. 6. After the ten minute period, have the students calculate the volume of water collected during the ten minutes. 7. Using the volume of water they calculated, have the students determine the rate at which ice melted during the ten minutes. 8. Using their calculate rate at which ice melts, have the students determine at what time Frosty (the ice) was taken out of the freezer. Discussion Questions: 1. When Frosty taken out of the Freezer? 2. How did you determine this? 3. Could scientists use something similar to determine the age of fossils? 4. What do you think absolute dating means? 5. How does absolute dating differ from relative dating? Assessment

14 1. Define absolute dating on a test. 2. After the lab, have students write a paragraph relating the lab to absolute dating. Extensions: For further activities on radiometric dating, see Frank McKinney s website Determining Age of Rocks and Fossils. RESOURCES/REFERENCES: Frosty the Snowman Meets His Demise: An Analogy to Carbon Dating. Science NetLinks. 20 October April < Where has all the carbon gone? Secrets of the Dead Public Broadcasting Service. 15 April < SUNSHINE STATE STANDARDS: SC.6.N.1.4 SC.6.N.1.5 SC.7.E.6.3

15 Name(s) Date The Fall of Frosty: An Analogy Carbon Dating to Frosty the Snowman decided to visit our classroom. However, because he is made of snow, he can only be out of the freezer for a short period of time. Unfortunately, someone took Frosty out of the freezer too soon, and now he lies melting at your lab station. The local police department has asked for you help in solving this mystery. In order to discover who committed this offense, you need to determine at what time Frosty was taken out of the Freezer. Directions: 1. Record the time 2. Record your initial volume in your graduate cylinder: ml 3. Start the stopwatch. Record the volume in the cylinder every minute for a total of 10 minutes. Time in minutes Volume in ml Time in minutes Volume in ml Calculate the volume of water melted from the ice during the ten minutes. Volume of Water = Volume after 10 minutes Initial Volume = ml

16 5. Calculate the rate at which the ice melted during the ten minute period. Rate = Volume of Water / 10 minutes = ml/min 6. Use the melting rate of ice you calculated in question 5 to determine how long ago Frosty was taken out of the freezer.