1. Understanding Rock Characteristics
1.9

2. Warm-Up
Many years ago, an entire city in Italy was found buried. Ancient cities are often buried over time, so this isn’t always unusual. What was strange about this city is that much of it was buried by solid rock, not dirt. Also strange was the fact that people were found inside their houses in this buried city. What do you think might have happened in this city?

3. Looking at Rock Evidence from a Mysterious City
Purpose: Students consider how the characteristics observed in rock can reveal clues about how the rock formed. Students investigate evidence gathered from rocks and geologic features in and near Pompeii, which lead geologists to make the convincing claim that a significant volcanic eruption in nearby Mt. Vesuvius destroyed the town in 79 AD.  

4. 1. Project Slide 1: Mt. Vesuvius and introduce a mystery about the city that disappeared. Say, “I am going to present a mystery that scientists tried to solve for hundreds of years. They made claims and gathered evidence about rock characteristics until they finally thought they had the best explanation for what happened. This is a mystery about a city that disappeared.” 

5. 2. Project Slide 2: Pompeii and introduce the discovery of the city
2. Project Slide 2: Pompeii and introduce the discovery of the city. Say, “In 1749, workers were digging in the countryside of Italy and accidentally uncovered a large object, which turned out to be the walls of a building. Over the next 150 years, archaeologists continued to dig in this site, uncovering an entire city.”

6. 3. Project Slide 3: Human Remains
3. Project Slide 3: Human Remains. Say, “Inside the city were the remains of all the people who had lived there many, many years ago. They were found buried doing normal, everyday things, such as sleeping. One man was even found pulling bread out of an oven.”

7. 4. Project Slide 4: Dog Remains
4. Project Slide 4: Dog Remains. Say, “A dog was found lying inside a house.”

8. What do you think happened in this mysterious city?
Think Pair Share
What do you think happened in this mysterious city?
After discussing with a partner, have students share their ideas with the class (if time allows).

9. Geologists put the story together using EVIDENCE
After this discovery, geologists and other scientists wondered what destroyed this city.
To understand what happened, they had to put together many pieces of evidence—about the rocks and other geologic features in the area—in order to make an argument.

10. Project Slide 5: Human Remains
Project Slide 5: Human Remains. Tell students: “One piece of evidence that geologists used was the characteristics of the rock in which the remains were covered. By making careful observations, they noticed that the remains were covered in rock made of small pieces of ash from a volcanic eruption.”
Explain that other rock formations nearby were also covered in this ash.  Say, “Geologists also looked at other rock formations around the city and found many other igneous rocks. After observing and analyzing the rock, they discovered that these rocks formed at the same time by the same geologic process.”

11. Project Slide 6: Mt. Vesuvius from Above
Project Slide 6: Mt. Vesuvius from Above. Say, “Geologists also knew that there was an active volcano very close to where the city was located. In the past, people had recorded observations of the volcano erupting. One person’s observation of an eruption in the area took place around the same time that scientists believe the rock formed.”

12. So what happened?
Discuss with your shoulder partner what you think happened using the provided evidence.

13. How geologists figured it out
After studying the characteristics of the rock carefully, both in the rock formations, in the remains, and around the city, geologists were able to claim that the city was destroyed by a sudden volcanic eruption.
In fact, there was so much evidence recorded in the rocks that geologists were able to confidently record the events of that day in 79 AD, hour-by-hour!

14. Observing and Discussing the Characteristics of Sedimentary, Metamorphic, and Igneous Rock
Guiding Question:
How do rocks record evidence of how they’ve formed and changed over time?
Purpose: Students make careful observations of photographs of different samples of sedimentary, metamorphic, and igneous rock. Groups then engage in an oral argumentation activity to describe some common characteristics of each rock type, based on their observations of the given rock samples.  1. Introduce new guiding question. Read aloud the new guiding question that you posted on the concept wall, “How do rocks record evidence of how they’ve formed and changed over time?” Let students know that the work they do today will help them identify evidence in rocks that may help them answer this question.

15. Today’s Activity
Like the geologists that studied the rocks in Pompeii, you are going make careful observations of rocks.
Practicing this skill today will help you solve the Grand Canyon Mystery, which you will work on in a later class
2. Link geologists’ work with the Pompeii mystery to what students will do in this session. Say, “Like the geologists that studied the rocks in Pompeii, you are going make careful observations of rocks. Practicing this skill today will help you solve the Grand Canyon Mystery, which you will work on in a later session.”  3. Introduce rock observation activity. Have students turn to pages 34–36, Sedimentary Rock Formations, Metamorphic Rock Formations, Igneous Rock Formations, in their notebooks. Explain that pairs will observe the characteristics of three types of rocks—sedimentary, metamorphic, and igneous. Instead of actual rock samples, each pair will receive a set of cards with photos representing four rock samples for each of the three rock types. In the tables in the notebook, each student will record the color and at least two observations for each rock. Encourage students to observe the photos for texture, grains, and whether the rock is shiny or dull.

16. Mineral
Smaller piece of matter from which rocks are made.

17. 4. Project Slide 7: Comparing Rock Types and remind students about the distinction between sediment grains and mineral grains. Say, “Sediment grains are stuck together, but don’t fit together. Mineral grains fit together like a puzzle. This happens because of the processes involving heat and/or pressure that form these rocks. When you make your observations, be sure to notice how the sediment grains in sedimentary rocks are different from the mineral grains in metamorphic and igneous rocks.”

18. 5. Project Slide 8: Sedimentary Rocks Cards and distribute card sets
5. Project Slide 8: Sedimentary Rocks Cards and distribute card sets. Distribute one set of Rock Type Cards to each pair. Explain that pairs will begin this activity by making observations of the characteristics of the four sedimentary rocks. They will then do the same for the four metamorphic rocks and then the four igneous rocks. 
6. Pairs make and record observations. Circulate and offer support as pairs discuss and then record their observations for each of the rocks on the cards. Allow approximately 10 minutes for pairs to make observations and record. Remind students that although they are discussing with a partner, each student should record observations in the tables in the notebook.

19. Common characteristics
Common characteristics are characteristics that you observe in some or all of the samples of ONE particular rock type.
7. Describe argumentation activity about common characteristics. Explain that each pair will join with another pair to form a group of four. Groups will use their observations to describe the characteristics that all sedimentary rocks have in common. They will then do the same with the metamorphic rocks and then with the igneous rocks. Explain that common characteristics are characteristics that they observed in some or all of the samples of ONE particular rock type. Let students know that there are many more rocks of each type than those represented in the cards. If students tried to observe all the rocks for all three types of rock, they would be looking at rocks for a long time!

20. Volunteer Time!
8. Ask for a volunteer to help model making claims about common characteristics from observations. Ask your volunteer partner to come up to the front of the room. Begin the modeling conversation.   Project Slide 9: Igneous Rocks Cards and make a claim based on observations. Point out the visible mineral grains on Rocks #2, #3, and #4 and say, “I made observations about the mineral grains in these igneous rocks. I observed that the mineral grains in Rocks #2, #3, and #4 are big enough to see. The only rock sample in which I couldn’t see the mineral grains is Rock #1. Therefore, I know that having visible mineral grains isn’t true of ALL igneous rocks. So, I claim that a common characteristic of igneous rocks is that they CAN have mineral grains that are big enough to see.” 
Model inviting your partner to agree, disagree, or add a new idea. Let students know that when one group member makes an observation, the other group members should either agree, disagree, or add a new idea. Ask your partner to model one of these things.

21. Rock Characteristic Sheet
Groups will discuss their observations of the four sedimentary rocks first.
Group members should agree on one common characteristic about which they feel most confident.
One group member will then record this on the student sheet.
Remember that you can refer back to your Rock Type Cards to help you resolve any disagreements.
9. Distribute Rock Characteristics student sheets. Distribute one Rock Characteristic student sheet to each group.  10. Students discuss common characteristics of sedimentary rocks. Explain that groups will discuss their observations of the four sedimentary rocks first. Group members should agree on one common characteristic about which they feel most confident. Invite students to use the sentence frames you wrote on the board. One group member will then record this on the student sheet. Remind students that they can refer back to their Rock Type Cards to help them resolve any disagreements.

22. 11. Project Slide 10: Rock Characteristics and discuss accepted common characteristics of sedimentary rock. Regain the class’ attention and have a student read aloud the characteristics of sedimentary rock. You may wish to have students record these characteristics on their groups’ charts. Say, “Here are three common characteristics of sedimentary rock that scientists often use to help them identify sedimentary rock. Which characteristics does your group agree with? Why? Are there characteristics your group would add?” Have students share their ideas with the class.  12. Students discuss common characteristics of metamorphic rock. Have students continue by discussing their observations about the metamorphic rocks and coming to agreement on one common characteristic. Have one group member record this on the student sheet. Remind them that they can use the sentence frames to guide their discussion. 

23. 13. Project Slide 11: Rock Characteristics and discuss accepted common characteristics of metamorphic rock.  Have a student read aloud the characteristics of metamorphic rock. Say, “Here are common characteristics of metamorphic rock that scientists often use to help them identify metamorphic rock. Which characteristics does your group agree with? Why? Are there characteristics your group would add?” Have students share their ideas with the class. 14. Students discuss common characteristics of igneous rock. Have students continue by discussing their observations about the igneous rocks and coming to agreement on one common characteristic. Have one group member record this on the student sheet. Remind them they can use the sentence frames to guide their discussion.    

24. 15. Project Slide 12: Rock Characteristics and discuss accepted common characteristics of igneous rock. Have a student read aloud the characteristics of igneous rocks. Say, “Here are common characteristics of igneous rock that scientists often use to help them identify igneous rock. Which characteristics does your group agree with? Why? Are there characteristics your group would add?” Have students share their ideas with the class. 16. Discuss common characteristics of all rocks. Point out the guiding question posted on the concept wall: How do rocks record evidence of how they’ve formed and changed over time? Let students know that they’ve just discussed ways to tell how rocks form. Say, “By observing rocks, we can tell how they formed. For example, we know that if we see a rock with minerals that fit together, we might be able to infer that the rock is metamorphic or igneous. If we see a rock made of sediment, we might make the inference that the sediment was buried and hardened into a rock over time. These kinds of inferences helped scientists figure out what happened to the city of Pompeii.” 

25. Section 4: Making Claims About a Mystery Rock (10 minutes) Purpose: In this section, students apply their understanding of common characteristics of each rock type to identify a mystery rock and tell the story of how it may have formed. 1. Project Slide 15: Mystery Rock and introduce the mystery rock. Explain that students will apply their new understanding about rock characteristics to this mystery rock, just as scientists who solved the Pompeii mystery did. The mystery rock might be any of the three rock types.  2. Explain the procedure. Partners will think and make observations for 2 minutes. After 2 minutes, partners will agree on a claim about whether the mystery rock is sedimentary, metamorphic, or igneous. Pairs will need to be prepared to defend their claims with evidence if they are called on.  3. Partners make observations. Circulate and encourage partners to discuss and share observations and thinking about what their observations make them think about how this rock was formed. Allow 2 minutes for quick discussion.  4. Partners agree on a claim. Have students agree on a claim. If they cannot agree on one claim they can say that the mystery rock is either X or Y but you’d prefer that they take a stand on only one type of rock. 5. Take class poll. Ask, “How many of you think this is a sedimentary rock? Metamorphic? Igneous?” Ask if there are any other claims (such as a combined claim) that students made. 6. Students share thinking about why they chose the claims they did. Ask students to raise their hands again if they thought the mystery rock was sedimentary rock. Call on one or two pairs to explain why they came to this conclusion, based on their observations and other thinking. (In this case, they are using their observations as evidence to support their claims.)  Follow the same procedure for metamorphic rock and then igneous rock. 7. Introduce homework. Have students turn to page 37, Homework: Making an Argument About a Mystery Rock, in their notebooks. Let them know that for homework, they will record their observations for the mystery rock, write a claim about what kind of rock it is, and support their claim with evidence, such as observations and their best, most convincing thinking. They can use the claim they came up with just now, or they can chose a new claim since they might have been convinced to think about the mystery rock differently after listening to what their peers just said.