Geologic Time

2. Era Age of reptiles and amphibians; ended with the mass extinction of dinosaurs
3. Era Earth's first era that began 4.6 billion years ago that includes creation of the Sun, Earth, the atmosphere, oceans and life
8. A scientist who studies fossils
9. fossil Evidence of the activities of ancient organisms
10. principle stating that Earth processes occurring today are similar to those that occurred in the past
17. Age the age of rocks and geologic features compared with other nearby rocks and features
18. film fossil Carbon outline of the organism
19. a piece of an older rock that becomes part of a new rock
20. Fossil a fossil representative of a species that existed on Earth for a short period of time, was abundant, and inhabited many locations
21. Fossil forms when a mold is filled with sediment
22. Preserved remains or traces of ancient organisms

1. remains Fossil actual remains of organisms
4. the idea that conditions and organisms on Earth change in quick, violent events
5. Fossils impression of an organism
6. a surface where rock has eroded away, producing a break, or gap, in the rock record
7. Era the part of geologic time 570-245 million years ago ; invertebrates, fishes, amphibians, reptiles, ferns, and cone-bearing trees were dominant
11. replacement fossil Copy of an organism made by mineral replacement
12. decay the process by which an unstable element naturally changes into another element that is stable
13. Age the numerical age, in years, of a rock or object.
14. the principle that in undisturbed rock layers, the oldest rocks are on the bottom
15. Life the time required for half of the amount of a radioactive parent element to decay into a stable daughter element
16. Era era that began about 65 million years ago, known as the "Age of Mammals"