1. The Geologic Time Scale and Early Earth Section Review

2. What is the geologic time scale? ► A record of the life forms and geological events in Earth’s history.

3. True or False? ► In order to develop the geologic time scale, scientists studied rock layers and fossils worldwide and placed Earth’s rock layers in order by relative age. Later, radioactive dating helped them determine the absolute ages of the divisions. ► TRUE!

4. What are the basic units into which the geologic time scale is divided? ►E►E►E►Era’s and periods

5. What are the 4 Era’s introduced in your book? ►P►P►P►Precambrian ►P►P►P►Paleozoic ►M►M►M►Mesozoic ►C►C►C►Cenozoic

6. True or False? ►S►S►S►Scientists hypothesize that Earth formed at a different time than the other planets and the sun around 2 million years ago. ►F►F►F►FALSE!!! ►T►T►T►The hypothesis states the Earth was formed at the same time as the other planets and the sun around 4.6 billion years ago!

7. What is a comet? ► A ball of dust and ice that orbits the sun.

8. How did volcanic eruptions and comets change Early Earth? ► They released carbon dioxide and water vapor into the atmosphere.

9. What do scientist think were the first organisms to evolve on Earth? ► Bacteria-like organisms