Across
- 3. the process of assigning an exact numerical age to an organism, object, or event
- 4. the process of placing objects or events in their proper order in time
- 6. life the time it takes for one half of a radioactive parent isotope to decay to its stable daughter isotope
- 7. 245 to 65 million years ago when the dinosaurs lived. Divided into triassic,jurassic, and cretaceous
- 8. 65 million years to present, sometimes called the age of mammals
- 9. states that the laws of nature operate today as they have in the past
- 11. gaps in the rock record during which either erosion occured or deposition is absent
- 12. period less than an era but more than an epoch, ex. jurassic
Down
- 1. time from earths beginning to the cambrian period (4.6 billion years ago to 541 million years ago)
- 2. states that in an undisturbed sequence of sedimentary rock layers the youngest rocks will be at the top and the oldest on the bottom
- 5. 544 to 245 million years ago when marine life was formed
- 10. the remains or traces of organisms found in the geologic rock record