2. History of the Earth CA Standard 8e Chapter 17

3. 17-1 The Age of the Earth Earth’s age is estimated at 4.6 billion years. James Hutton in 1788- proposed that features of the earth were influenced by volcanoes, erosion, etc.. These things all act very slowly

4. In 1830, Charles Lyell agreed that the earth had been shaped over a long period of time…but also stressed the importance of explaining theory in terms of scientific method.

5. Geologic Time Scale Relative Dating- the age of some rocks “relative” to others based on their position. NEWER: RECENTLY DEPOSITED OLDER: DEPOSITED EARLIER

6. Absolute Dating: using scientific techniques to find the approximate actual age of artifacts. Radioactive Dating: using the known rate of decay to calculate the age of artifacts. ( 14 C)

8. 17-1 The Fossil Record Fossils- preserved remains of ancient organisms Formation of fossils- when animals are buried in some medium that prevents decay –mud, sand, silt, tar pits –Sedimentary Rock

9. Specific conditions are required for fossils to form –mountains vs. rivers and streams –many organisms never fossilize Not all fossils have been found Problems with the Fossil Record:

10. The quality of fossils varies greatly As a result, the fossil record is not as complete as paleontologists would like

11. Cabrian: 500 million

12. Triassic: 250 million

13. Jurassic: 200 million

15. Trilobite

16. The Fossil Record Collectively, the millions of fossils that have been collected make up The Fossil Record Many pieces are missing Scientists have been able to construct detailed paths of change through time for many species

17. Evidence indicates that Earth’s climate has changed significantly over time Evidence also shows that species of plants and animals changed to fit those environments, or perished.