Relative Age with Edible Rocks Name: Activity

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1 Relative Age with Edible Rocks Name: Activity 4th grade PSI Science Activity Question How is relative age dating used when observing rock layers? Before You Begin How can we tell if one rock layer is older or younger than another? What is the Principle of Superposition?

2 Purpose During this experiment, you will observe edible rocks and their layers to better understand relative age dating and the Principle of Superposition. These edible rocks are a model of rock layers like we find in nature. You will sketch pictures of the rock layers and also think about the step-by-step process that led up to the rocks formation. (Remember to answer Lab Questions during class while you are engaged in the activity. Conclusion Questions can be answered after class.) Materials Bite size bars cut in half (2 halves per student) Procedure 1. Sketch a cross-section of your rocks. (show details) Rock 1 Rock 2

3 2. Draw step-by-step pictures of how one of your rocks formed. Rock # 1st 2nd 3rd 4th 3. Share your step-by-step drawing with a partner. Have them share their model with you. Discuss any similarities or differences you see in your drawings or in your thoughts about how the rock formed. 4. Prepare your ideas about how the rock formed to share with the class. You and your classmates will present ideas and vote on the most likely process of formation. Lab Questions 1. What is the oldest layer of these rocks? How do you know?

4 2. What is the youngest layer of these rocks? How do you know? 3. From looking at your rocks, can you tell exactly how old the rock layers are? (3 days, 2 years, 5 months?) Why or why not. 4. Using the step-by-step pictures you drew, explain how you think that rock formed.

5 Conclusion Questions 1. How are the edible rocks you examined similar to rocks found in nature? 2. How are they different? 3. Relative dating is the process of using layers of rock to find out if one layer of rock is older or younger than another layer of rock. Did you use relative dating during this activity? How does it relate to the Principle of Superposition?

6 TEACHER NOTES When picking bars to use for this activity, it is important to choose bars that have multiple layers. Some ideas for candy bars to use are: Snickers, Kit-Kat, Milky Way, and wafers. Snickers work very well and are one of the best candy bars to use if possible. This is because of the layer of caramel and peanut inside, which simulates a rock layers with fossils. Bars with just horizontal layers and no ingredients that model fossils will challenge students thinking less, but can be used alongside another bar that models this well. It is a good idea to have all students sketch the formation process (step #2) for the same candy bar so that ideas can be shared and compared. This part of the activity, having students draw step-by-step pictures of how a rock formed, can be a challenging question. Even though it might seem straightforward to draw a step-by-step process of how the edible rock formed, it is usually difficult for the students to grasp. Every student will have a different idea about how the rock formed, however, based on the available evidence, only a few scenarios are possible. So in short, you should look for students to: Draw the oldest layer first. Draw the next oldest layer second. Draw the next oldest layer next. (If using Snickers bars, this layer can be challenging since it contains peanuts inside of sediment, but allow students to make their best hypothesis.) Etc Remind students that laboratory questions should be answered while they are doing the activity, not afterwards.

7 Answer Key Answers to the Lab Questions: 1. What is the oldest layer of these rocks? How do you know? answers will vary depending on bars used because it is the layer at the bottom of all the layers 2. What is the youngest layer of these rocks? How do you know? answers will vary depending on bars used because it is the layer on the top of all the layers 3. From looking at your rocks, can you tell exactly how old the rock layers are? (3 days, 2 years, 5 months?) Why or why not. No, because you can only tell which layers are older or younger than each other. 4. Using the step-by-step pictures you drew, explain how you think that rock formed. answers will vary Answers to the Conclusion Questions: 1. How are the edible rocks you examined similar to rocks found in nature? The rocks have layers, contain particles in some layers, the layers are not all made of the same thing, display the Principle of Superposition. 2. How are they different? The layers are made of food not sediment, the layers have not cemented together as strongly as a rock does, the rock has probably formed much quicker than rocks in nature, it is easy to see the rock layers compared to in nature where it is more difficult. 3. Relative dating is the process of using layers of rock to find out if one layer of rock is older or younger than another layer of rock. Did you use relative dating during this activity? How does it relate to the Principle of Superposition? I did use relative dating during this activity. Relative dating and the Principle of Superposition go hand in hand; the Principle of Superposition can help you figure out a timeline of oldest to youngest within rock layers, and relative dating looks at specific layers and figures out their age in comparison to each other.