Earths History

2. Geologic time is divided best into units based on types of _____ living during certain periods
4. Which of these groups of animals appeared on Earth most recently?
8. Which of the following is least likely to become fossilized?
9. Trilobites can be used to study the passage of geologic time because __________ changed throughout time
12. Determining the order of events and the relative age of rocks by examining the position of rocks in a sequence is called __________.
13. Drift Fossils and rocks that are similar are found in Asia and Africa. This provides evidence of what?
14. With ________ dating, a rock’s exact age can be determined,whereas with ________ dating, a rock’s age is compared to the ages of other rocks.
16. The type of Earth material most likely to contain fossils is ____________.
17. The law that states in an undisturbed sedimentary rock layers,older layers of rock lie under younger rock layers is the
18. All of the following conditions help preserve organisms as fossils EXCEPT __________.

1. The half-life of Carbon-14 is 5730 years. What percent of parent material would be left after 5730 years?
3. Trilobite that lived for a short period of time and was abundant is an example of an
5. Radioactive dating is used to find the ____ of fossils
6. Unless the rock layers have been overturned or shifted, the top rock layer is the ______
7. The earliest part of Earth’s history is called the
10. A scientist wants to find the absolute, or actual age of a rock. Which of these is the scientist most likely to use?
11. To learn how Earth’s atmosphere has changed over time scientists study air bubbles in which of the following?
15. What is the longest division of earth's history?