Earth Science Chapter 12 Reading Guide
As you read the chapter, fill in the forms to complete this outline.
12.1: Discovering Earth’s History
A. A Brief History
1. The primary goal of geologists is to
2. In the 1600s James Ussher determined the earth was
years old.
3. In the 1700s James Hutton came up with the principle of
which states
4. What is meant by uniformitarianism?
B. Relative Dating
1. Relative dating means
2. Relative dating tells us
3. What is the Law of Superposition?
4. What is the Principle of Original Horizontality?
5. State the Law of Cross-Cutting Relationships:
6. What are inclusions?
7.
represent long periods of time during which deposition stops, erosion occurs for some time, then
deposition resumes.
8. What is deposition?
9. The process by which rock layers in different regions are matched is called
12.2: Fossils
What are fossils?
A. Fossil Formation
1. What determines the type of fossil formed?
2. What are ‘unaltered remains’?
Give an example:
3. What are ‘altered remains’?
Give an example:
4. A fossil mold is created when
5. A cast fossil is created if
6. Carbonization occurs when an organism
7. What are trace fossils?
8. The principle of fossil formation states that fossil organisms
9. What is meant by ‘index fossil’?
10. The three characteristics of index fossils are:
a.
b.
c.
12.3: Radioactive Dating
1. What makes an element radioactive?
2. What happens to the nucleus of a radioactive element?
3. What is meant by the half-life of an element?
4. The procedure of calculating the ages of rocks is called
5. Each radioactive isotope has been decaying at a
since
6. What is the radioactive isotope of carbon?
7. Radioactive carbon can be used to date
earth history because its half-life is
years.
12.4: The Geologic Time Scale
How old is the earth thought to be?
A. Structure of the Time Scale
1. Geologic time is divided into
,
,
, and
2.
represent the greatest expanses of time.
3. The 3 eons of Precambrian time are:
a.
b.
c.
4. The Phanerozoic eon is divided into three eras:
a.
b.
c.
5. Each era is divided into shorter time periods called
6. Only the Cenozoic has
which are smaller subdivisions of periods.
7. What determines the ending of any of these time periods?