Earth's History

2. When minerals fill in the hollows of an organism
8. To undergo changes and development.
10. Forms when the mud or sand hardens to stone where a footprint, trail, or burrow of an organism was left behind.
11. A mark or depression made by pressure.
13. leaves carbon imprint in the rock.
16. ("The Age of Mammals") from 65 million years ago to today
17. Forms when minerals soak into the buried remains and changes them into rock
18. It is the time from when the Earth formed and simple life-forms evolved.
20. A series of dinosaur footprints preserved in a rock.
21. The time it takes for half the atoms in a sample of a radioactive element to decay to a stable end product.
23. The layers of sedimentary rock that form after particles settle out of a fluid and are compressed over time
24. The preserved remains or evidence of prehistoric animals.
25. A specialized feature that makes an animal or plant better suited to its particular environment.

1. When a leaf, feather, bone or even a body of an organism leaves an imprint on sediment, which hardens and becomes rock
3. An element that is the product of radioactive decay
4. The fossilized remains of organisms that lived and died within a particular time segment of Earth's history and that can be used to correlate rock layers.
5. trapped in rock, ice, tar, or amber
6. The scientific study of the Earth
7. a method of dating geological or archeological specimens by determining the relative proportions of particular radioactive isotopes present in a sample.
9. ("The Age of Ancient Life") occurred 600 to 245 million years ago
12. ("The Age of Reptiles") occurred from 245-65 million years ago
14. Fuels formed by the remains of dead plants and animals
15. The process of placing events in the sequence in which they occurred; does not identify actual dates
19. No longer living anywhere on earth.
22. a fossil reptile of the Mesozoic era, often reaching an enormous size