Skills Worksheet Directed Reading A Section: Relative Dating: Which Came First? Write the letter of the correct answer in the space provided. 1. Determining the age of objects or events in relation to other objects or events is called a. relative sequencing. b. relative dating. c. relative history. d. relative geology. THE PRINCIPLE OF SUPERPOSITION 2. As long as a sequence of rock layers is undisturbed, scientists know that a. older rocks lie above younger rocks. b. younger rocks lie under older rocks. c. younger rocks lie above older rocks. d. older rocks have eroded away. 3. The principle that states that younger rocks lie above other rocks in undisturbed sequences is called a. relative dating. b. superposition. c. uniformitarianism. d. catastrophism. 4. How do disruptions of rock sequences pose a challenge to geologists? THE GEOLOGIC COLUMN 5. What is the geologic column? 6. How do geologists use the geologic column? Holt Science and Technology 3 The Rock and Fossil Record
Directed Reading A continued DISTURBED ROCK LAYERS 7. Explain how a crosscutting feature is always younger than the rock layers it cuts across. Match the correct description with the correct term. Write the letter in the space provided. 8. a break in the Earth s crust along which blocks of crust slide relative to one another 9. younger sediment deposited on top of older layers 10. molten rock that has squeezed into existing rock and hardened a. superposition b. folding c. fault d. tilting e. intrusion 11. rock layers bent and buckled by the Earth s internal forces 12. rock layers slanted by the Earth s internal forces but without folding GAPS IN THE RECORD UNCONFORMITIES 13. When a layer or several layers of rock are missing from a rock-layer sequence, this is called a(n). 14. Name two possible explanations for a missing layer in a rock-layer sequence. 15. When sediment stops at some point and restarts, an unconformity is created by. 16. An unconformity is created when an area is uplifted and exposed to by wind and water. Holt Science and Technology 4 The Rock and Fossil Record
Directed Reading A continued TYPES OF UNCONFORMITIES Match the correct description with the correct term. Write the letter in the space provided. 17. found between horizontal layers of sedimentary rock and rock layers that have been tilted or folded 18. where sedimentary rock layers lie on top of an eroded surface of older intrusive igneous or metamorphic rock a. disconformity b. nonconformity c. angular unconformity 19. most common type of unconformity ROCK-LAYER PUZZLES 20. How do geologists figure out rock-layer puzzles? Holt Science and Technology 5 The Rock and Fossil Record
Skills Worksheet Section Review Relative Dating: Which Came First? USING KEY TERMS 1. In your own words, write a definition for each of the following terms: relative dating, superposition, and geologic column. UNDERSTANDING KEY IDEAS 2. Molten rock that squeezes into existing rock and cools is called a(n) a. fold. b. fault. c. intrusion. d. unconformity. 3. List two events and two features that can disturb rock-layer sequences. 4. Explain how physical features are used to determine relative ages. Holt Science and Technology 40 The Rock and Fossil Record
Section Review continued CRITICAL THINKING 5. Analyzing Concepts Is there a place on Earth that has all the layers of the geologic column? Explain. 6. Analyzing Methods Disconformities are hard to recognize because all the layers are horizontal. How does a geologist know when he or she is looking at a disconformity? INTERPRETING GRAPHICS 7. Look at the diagram below. If the top rock layer were eroded and deposition later resumed, what type of unconformity would mark the boundary between older rock layers and the newly deposited rock layers? Holt Science and Technology 41 The Rock and Fossil Record