Across
- 2. commonly used to determine age of rocks
- 4. can be dated directly useing carbon
- 6. found in layers closely associated with fossilbearing
- 9. dont have enough radioisotope left to date accuratly
Down
- 1. a half life of 4510 million years
- 2. can be used for radiometeric dating are found only in ignious or metemorphic rocks
- 3. to the daughter isotope to determine the age of the sample
- 5. the radioactive isotope and its decay product must be known
- 7. used to date organic substances such as bones and tissue
- 8. the amount of time it takes for half of the original to decay