Across
- 5. How long a star will live based on the mass of it.
- 8. A very long period of time.
- 11. Period of time known as a half-life.
- 12. A long and distinct period of history.
- 13. Lighter elements join to form heavier elements.
- 14. Many different points in history continents were located close to each other.
- 16. Came up with the idea that Earth's continents were not always in their current locations.
- 18. A rock's age compared to the ages of the rocks around it.
Down
- 1. Exact number of years since the rock formed.
- 2. Star begins to run out of fuel.
- 3. Large number of species disappearing in a short time.
- 4. The amount of time it takes for half of the radioactive atoms to go away.
- 6. Lakes were formed due to glaciation.
- 7. Protons and neutrons that joined together to form elements.
- 9. Typically small changes that occur slowly on Earth.
- 10. To tell if an object is moving toward or away from us.
- 15. Glaciers covered large parts of Earth's surface.
- 17. A universe formed billions of years ago.