Figure 1 illustrates a cross-section of rock layers with different types of rocks and fossils, used to determine relative ages of geological materials.
Cross-sectional view of rock layers in Figure 1 showing various geological formations including red sandstone, tan limestone, gray limestone, brown sandstone, black shale, green shale, gray shale, trilobite fossil, snail fossil, dinosaur bone, and a gabbro dike.
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Show Answer Key & Explanations
Step-by-step solution for: Earth Science Study Note Unit 1 Interactive Worksheet - Edform
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Show Answer Key & Explanations
Step-by-step solution for: Earth Science Study Note Unit 1 Interactive Worksheet - Edform
Let's solve this step-by-step based on the principles of relative dating and the cross-sectional diagram provided in Figure 1.
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1. Natural laws govern the way geologists determine the age of rock deposits. This technique is called ___
→ Relative dating
*Explanation:* Relative dating uses principles like superposition, original horizontality, and cross-cutting relationships to determine the sequence of events without assigning exact numerical ages.
2. The principle of ____ states that an older rock layer and things buried in it occur beneath younger layers unless the layers have been disturbed.
→ Superposition
*Explanation:* The Law of Superposition says that in undisturbed sedimentary sequences, the oldest layers are at the bottom and the youngest are on top.
3. Some rock layers are incomplete. The gaps are called ____
→ Unconformities
*Explanation:* Unconformities represent missing time in the geological record due to erosion or non-deposition.
4. A common cause of gaps in rock layers is ____
→ Erosion
*Explanation:* Erosion removes rock layers over time, creating gaps (unconformities) in the geological record.
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We use the principle of superposition, cross-cutting relationships, and fossil succession.
Let’s analyze Figure 1:
#### Layer order from bottom to top (oldest to youngest):
1. Gray shale (bottom)
2. Green shale
3. Black shale
4. Brown sandstone (in two places; appears above black shale)
5. Tan sandstone
6. Gray limestone
7. Tan limestone
8. Red sandstone (topmost)
9. Dinosaur bone (in tan limestone)
10. Gabbro dike – cuts through brown sandstone and green shale → so it's younger than both
11. Fossils:
- Trilobite fossil → in gray shale
- Snail fossil → in black shale
- Dinosaur bone → in tan limestone
Now let’s answer each question:
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5. tan sandstone and brown sandstone
→ Brown sandstone
*Reason:* Brown sandstone is below tan sandstone → older by superposition.
6. brown sandstone and gray limestone
→ Brown sandstone
*Reason:* Brown sandstone is below gray limestone → older.
7. gabbro dike and brown sandstone
→ Brown sandstone
*Reason:* Gabbro dike cuts through brown sandstone → so the dike is younger. Therefore, brown sandstone is older.
8. gabbro dike and gray shale
→ Gray shale
*Reason:* Gabbro dike cuts through gray shale → so gray shale is older.
9. snail fossil and trilobite fossil
→ Trilobite fossil
*Reason:* Trilobites lived earlier (Paleozoic), snails evolved later. Also, trilobite is in gray shale, snail in black shale, and gray shale is below black shale → so trilobite fossil is older.
10. snail fossil and dinosaur bone
→ Snail fossil
*Reason:* Snail fossil is in black shale (lower), dinosaur bone is in tan limestone (higher). So snail fossil is older.
11. snail fossil and green shale
→ Green shale
*Reason:* The snail fossil is within the black shale, but the green shale is directly below the black shale → so green shale is older than the black shale, thus older than the snail fossil.
Wait! Let's clarify:
- Green shale is below black shale.
- Snail fossil is in black shale.
→ So green shale is older than snail fossil.
✔ Answer: Green shale
12. dinosaur bone and red sandstone
→ Dinosaur bone
*Reason:* Dinosaur bone is in tan limestone, which is below red sandstone → so dinosaur bone is older.
13. red sandstone and gray limestone
→ Gray limestone
*Reason:* Gray limestone is below red sandstone → older.
14. tan limestone and tan sandstone
→ Tan sandstone
*Reason:* Tan sandstone is below tan limestone → older.
15. tan limestone and gray limestone
→ Gray limestone
*Reason:* Gray limestone is below tan limestone → older.
16. The type of unconformity shown in Figure 1 is a(n) ____
→ Angular unconformity
*Explanation:* The lower layers (like gray shale, green shale) are tilted, while the overlying layers (brown sandstone, etc.) are horizontal. This indicates that the older layers were folded/tilted, eroded, then new horizontal layers were deposited on top. That’s an angular unconformity.
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1. Relative dating
2. Superposition
3. Unconformities
4. Erosion
5. Brown sandstone
6. Brown sandstone
7. Brown sandstone
8. Gray shale
9. Trilobite fossil
10. Snail fossil
11. Green shale
12. Dinosaur bone
13. Gray limestone
14. Tan sandstone
15. Gray limestone
16. Angular unconformity
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Let me know if you'd like a labeled version of the figure or explanation of any concept!
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Part 1: Fill-in-the-blank questions
1. Natural laws govern the way geologists determine the age of rock deposits. This technique is called ___
→ Relative dating
*Explanation:* Relative dating uses principles like superposition, original horizontality, and cross-cutting relationships to determine the sequence of events without assigning exact numerical ages.
2. The principle of ____ states that an older rock layer and things buried in it occur beneath younger layers unless the layers have been disturbed.
→ Superposition
*Explanation:* The Law of Superposition says that in undisturbed sedimentary sequences, the oldest layers are at the bottom and the youngest are on top.
3. Some rock layers are incomplete. The gaps are called ____
→ Unconformities
*Explanation:* Unconformities represent missing time in the geological record due to erosion or non-deposition.
4. A common cause of gaps in rock layers is ____
→ Erosion
*Explanation:* Erosion removes rock layers over time, creating gaps (unconformities) in the geological record.
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Part 2: Compare materials — which is older?
We use the principle of superposition, cross-cutting relationships, and fossil succession.
Let’s analyze Figure 1:
#### Layer order from bottom to top (oldest to youngest):
1. Gray shale (bottom)
2. Green shale
3. Black shale
4. Brown sandstone (in two places; appears above black shale)
5. Tan sandstone
6. Gray limestone
7. Tan limestone
8. Red sandstone (topmost)
9. Dinosaur bone (in tan limestone)
10. Gabbro dike – cuts through brown sandstone and green shale → so it's younger than both
11. Fossils:
- Trilobite fossil → in gray shale
- Snail fossil → in black shale
- Dinosaur bone → in tan limestone
Now let’s answer each question:
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5. tan sandstone and brown sandstone
→ Brown sandstone
*Reason:* Brown sandstone is below tan sandstone → older by superposition.
6. brown sandstone and gray limestone
→ Brown sandstone
*Reason:* Brown sandstone is below gray limestone → older.
7. gabbro dike and brown sandstone
→ Brown sandstone
*Reason:* Gabbro dike cuts through brown sandstone → so the dike is younger. Therefore, brown sandstone is older.
8. gabbro dike and gray shale
→ Gray shale
*Reason:* Gabbro dike cuts through gray shale → so gray shale is older.
9. snail fossil and trilobite fossil
→ Trilobite fossil
*Reason:* Trilobites lived earlier (Paleozoic), snails evolved later. Also, trilobite is in gray shale, snail in black shale, and gray shale is below black shale → so trilobite fossil is older.
10. snail fossil and dinosaur bone
→ Snail fossil
*Reason:* Snail fossil is in black shale (lower), dinosaur bone is in tan limestone (higher). So snail fossil is older.
11. snail fossil and green shale
→ Green shale
*Reason:* The snail fossil is within the black shale, but the green shale is directly below the black shale → so green shale is older than the black shale, thus older than the snail fossil.
Wait! Let's clarify:
- Green shale is below black shale.
- Snail fossil is in black shale.
→ So green shale is older than snail fossil.
✔ Answer: Green shale
12. dinosaur bone and red sandstone
→ Dinosaur bone
*Reason:* Dinosaur bone is in tan limestone, which is below red sandstone → so dinosaur bone is older.
13. red sandstone and gray limestone
→ Gray limestone
*Reason:* Gray limestone is below red sandstone → older.
14. tan limestone and tan sandstone
→ Tan sandstone
*Reason:* Tan sandstone is below tan limestone → older.
15. tan limestone and gray limestone
→ Gray limestone
*Reason:* Gray limestone is below tan limestone → older.
16. The type of unconformity shown in Figure 1 is a(n) ____
→ Angular unconformity
*Explanation:* The lower layers (like gray shale, green shale) are tilted, while the overlying layers (brown sandstone, etc.) are horizontal. This indicates that the older layers were folded/tilted, eroded, then new horizontal layers were deposited on top. That’s an angular unconformity.
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✔ Final Answers:
1. Relative dating
2. Superposition
3. Unconformities
4. Erosion
5. Brown sandstone
6. Brown sandstone
7. Brown sandstone
8. Gray shale
9. Trilobite fossil
10. Snail fossil
11. Green shale
12. Dinosaur bone
13. Gray limestone
14. Tan sandstone
15. Gray limestone
16. Angular unconformity
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Let me know if you'd like a labeled version of the figure or explanation of any concept!
Parent Tip: Review the logic above to help your child master the concept of 9th grade earth science worksheet.
