Across
- 2. a solid copy of the shape of an organism
- 5. age of a rock when compared to other rocks
- 9. the process by which all the different kinds of living things have changed over long periods of time
- 11. one of the units of geologic time into which geologists divide eras
- 17. states that the oldest layer is at the bottom in an undisturbed horizontal layer of sedmintary rocks
- 19. the atoms of one element break down to form atoms of another element
- 21. the surface where new rock layers meet a much older rock surface beneath due to erosion
- 22. hollow area in a sediment in the shape of an organism
- 23. a fossil that is widely distributed and only existed a short period of geological time
Down
- 1. scientist who studies fossils
- 3. provides evidence of the activities of ancient organisms
- 4. extremely thin coating of carbon on rock that preserves delicate parts of plant or insect
- 6. a break in the Earth's crust
- 7. a record of the geologic events and the evolution of life
- 8. remains of organisms in tar, amber, or ice
- 10. one of three long units of geologic time between the Precambrian and the present
- 12. magma that cools and hardens within a rock layer
- 13. lava that hardens on the surface and forms igneous rock
- 14. fossils in which minerals replace all or part of an organism
- 15. the number of years that have passed since a rock formed
- 16. preserved remains or traces of living things
- 18. the time it takes for half of the radioactive atoms to decay
- 20. refers to any species that longer exists on Earth