Across
- 3. Subdivisions of geologic time.
- 6. A system of chronological dating that relates geological strata to time.
- 8. The theory that changes in the earth's crust during geological history have resulted from the action of continuous and uniform processes.
- 11. A method for determining the age of an object containing organic material by using the properties of radiocarbon.
- 13. Time taken for the radioactivity of a specified isotope to fall to half its original value.
Down
- 1. Spontaneous emission of radiation, either directly from unstable atomic nuclei or as a consequence of a nuclear reaction.
- 2. The preserved remains or traces of animals, plants and other organisms from the past.
- 4. A unit of time equal to 1 billion years.
- 5. Any method of determining the age of organic materials based on measurement of short-lived or long-lived radioactive elements.
- 7. The beginning of a distinctive period.
- 9. The science of determining the relative order of past events.
- 10. A fossil that is good for dating and understanding the strata in which it is found.
- 12. A long and distinct period of history with a particular feature or characteristic.