Geologic Time Crossword

3. The Eon in which Earth’s Land, Water, and Atmosphere were formed.
5. The new substance that the parent element changes into during radioactive decay.
8. Layers of rock are laid down in a horizontal arrangement.
10. The Era where Fish evolved.
11. The youngest geologic feature cuts through the older feature.
12. The Eon in which ancient life, one-celled organisms appeared.
15. The time that it takes for one half of the parent element to change into the daughter element.
16. The break down of radioactive elements.
18. In a layer of rocks, the youngest layer is on the top and oldest is on the bottom.
20. The starting substance of radioactive decay.
22. The smallest unit of Geologic Time.
23. The largest unit of Geologic Time.
24. Fossil of known age that is used in relative dating.

1. The type of rock that is used in Radioactive Dating.
2. The oldest Eon in which the Earth was formed.
4. A table that organizes Earth’s History into Units of Time.
6. Provides numerical value for the age of historical events or objects.
7. A gap in the rock record caused by periods of deformation and erosion.
9. The present is the key to the past.
13. Dating method that identifies the order that events occurred and does not provide an exact value.
14. Type of radiometric dating that is used for once living material.
17. The youngest Eon in which modern life formed.
19. The Era when Mammals and Humans appeared.
21. The Era when Dinosaurs appeared.