Across
- 3. rock fragment is older than rock it's in
- 6. the exact age of a rock
- 7. how long it takes for half an atom to decay
Down
- 1. remains of living things
- 2. any feature that cuts across is younger
- 3. a fossil that lived in an immense area but for a short time period
- 4. Youngest on top oldest on bottom
- 5. not exact age