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Unit 4A Lesson 5

Unit 4A Lesson 5 Quiz

Name two gases common in Earth's atmosphere during the Precambrian time? Hydrogen and Helium
Scientists used index fossils and rock layers worldwide to determine the: Geologic Time Scale
What is a body fossil? A rare fossil in which the entire organism gets preserved.
What is an Index Fossil? Fossils of organisms that were common worldwide but only lived for a defined period of time in the geologic time scale
On a graph of strontium 90, after two half lives how much radioactive material would remain in a sample? 1/4 or 25%
When did Earth's atmosphere, oceans, and continents began to develop? During the first several hundred million years of Precambrian time
How are fossils most commonly formed? When a living thing dies and is quickly covered in sediment
What is a petrified fossil? Fossils formed when minerals replace all or parts of an organisms body.
What is a mold fossil? A hollow shape formed when sediment hardens around an organism which later decays
What is a cast fossil? A solid shape of an organism formed when sediment hardens inside of a hollow mold.
Name 6 types of Fossils that we studied in Unit 4. Mold, Cast, Index, Petrified, Body , Trace
Carbon 14 and Strontium 90 are two examples of Radioactive elements that scientists use to determine: The absolute age of a rock or fossil.
What is the absolute age of a rock or fossil It's actual age in years. (a number- usually in 'mya')
What is the relative age of a rock or fossil? Its age compared to other rock layers (older/younger)
On a graph of Radioactive decay, at point 0 years, how much radioactive material would remain in a sample? 100% At pt 0, Radioactive decay has JUST begun. Either a living organism has just died OR an igneous rock has just formed.
Created by: scanto