Chapter 8
Essential Questions: How is relative and absolute age determined and used to interpret Earth’s geologic history and
a geologic history diagram? How is the evolution and history of life present on Earth explained?
Vocabulary: uniformitarianism
Relationships
absolute age
relative age
Law of Superposition unconformity
Law of Crosscutting
varve radiometric dating
half-life
Law of Horizontality fossil
trace fossil
index fossil
ES SOL: SOL 9 The student will investigate and understand that many aspects of the history and evolution of
Earth and life can be inferred by studying rocks and fossils. Key concepts include:
a) traces and remains of ancient, often extinct, life are preserved by various means in many
sedimentary rocks;
b)
superposition, cross-cutting relationships, index fossils, and radioactive decay are methods of
dating bodies of rock; absolute and relative dating have different applications but can be used
together to determine the age of rocks and structures
Objectives: ES.9.1 Recognize that traces and remains of ancient, often extinct, life are preserved by various
means in many sedimentary rocks
ES.9.2 Explain superposition, cross-cutting relationships, index fossils, and radioactive decay as methods of
dating bodies of rock
ES.9.3 Explain that absolute and relative dating have different applications but can be used together to
determine the age of rocks and structures
Review
1. What is a fossil? Can a fossil be made of everything that dies?
2. What kind of rock do you find fossils in?
3. How do scientists use fossils?
4. How is a fossil formed?
5. what is the difference between a mold and a cast?
6. What is petrifaction? Give an example.
7. What is an imprint? Give an example.
8. Give examples of preservation of the entire organism. (original preservation)
9. Explain how an index fossil is used to determine age of surrounding area.
10. What is the difference between an index fossil and a trace fossil?
11. What is the Principle of uniformitarianism?
12. Explain how geologists use the Law of Superposition, Law of Crosscutting Relationships, and the Law of
Horizontality to determine the relative age of rocks.
13. What is the difference between absolute and relative dating?
14. Correlate the rock structure.
15. What is an unconformity and what is the difference between the kinds?