Across
- 4. A trace of an ancient organism that has been preserved in rock.
- 5. Change in a kind of organism over time; process by which modern organisms have descended from ancient organisms.
- 10. a rock formation that is visible on the surface
- 11. The principle that states that each rock layer is older than the layer above it and younger than the layer below it
- 12. era that began about 66 million years ago, known as the "Age of Mammals"
- 13. A term that typically describes a species that no longer has any known living individuals.
Down
- 1. middle life (245-144 million years ago), rise and then extinction of dinosaurs
- 2. The age of a rock compared to the ages of rock layers
- 3. a method of expressing a quantity as a number multiplied by 10 to the appropriate power
- 6. The age of a rock given as the number of years since the rock formed.
- 7. A place where an old, eroded rock surface is in contact with a newer rock layer. A gap in the rock record.
- 8. a diagram that shows a cut through the surface of the earth
- 9. the part of geologic time 570-245 million years ago when trilobites thrived