Across
- 5. remains of plants and animals that have been altered very little since the organisms' deaths
- 7. fossils that are easily recognized, abundant, and widely distributed geographically
- 8. created when a mold later becomes filled with material
- 12. scientist use C-14 to determine the age of organic materials, which contain abundant carbon
- 13. the pore spaces of an organism's buried hard parts are filled with minerals from groundwater
- 15. change in species over time
Down
- 1. scientists date an object using radioactive isotopes
- 2. shells, bones, or cell walls, are most common type of fossil, and can form from two processes
- 3. science of using tree rings to determine absolute age
- 4. emission of radioactive particles and the resulting change into other isotopes over time
- 6. indirect fossils, traces of worm trails, footprints, and tunneling burrows
- 9. length of time it takes for one half of the original parent isotope to decay
- 10. forms when sediments cover the original hard part of an organism such as shell, and the hard part is later removed by erosion or weathering
- 11. bands of alternating light and dark colored sediments of sand, clay, and silt
- 14. enables scientist to determine the numerical age of rocks and other objects