Earth's History Review

5. describes the order in which fossils were formed, compared to each other
8. fossils used to determine relative age
10. any fossil that is not of the organism itself
13. movement in the mantle responsible for the movement of the crust
15. two-dimensional fossil, usually formed from soft-bodied organisms
18. fossilized imprints; hollow
19. the amount of time it takes for half of the radioactive elements to decay
20. three-dimensional fossils; filled in molds
21. the oldest layers of rock are found at the bottom
22. the supercontinent that Wegner predicted
23. fossils of an organism with little or no change
24. two plates slipping past each other
25. describes the amount of time since a rock or fossil was formed

1. fossils formed when minerals replace the organism, but the original structure is maintained
2. two plates moving apart
3. two plates colliding
4. the plate around which you can find the Ring of Fire
6. a gap in the geologic record
7. a layer of cooled lava that becomes part of the rock layer
9. scientist who studies the history of life on Earth through the fossil record
11. method to determing the age of fossils up to 60,000 years
12. location of 90% of earthquakes and 75% of active volcanoes
14. the element that carbon-14 decays into
16. an element that is unstable, and breaks down over time
17. a collection of cooled magma that does not reach the surface, but becomes a part of the rock layer