Geological History

2. it is the time it takes for a radioactive element for half of the elements to decay
6. a process that preserves entire organisms, i.e. tar, tree resin, freezing - a fossil type
9. the preserved remains or traces of living things
12. fossils in which minerals replace all of an organism or part of an organism such as a dinosaur bone - a fossil type
14. the age of a rock compared to other rocks, i.e. older or younger than
15. when an organism no longer exists and will never again on earthv

1. used to determine the relative age of a rock. It states that in undisturbed horizontal sedimentary rock layers the oldest is at the bottom Each higher layer is younger than the one below it.
3. a gap in the geological record that shows where rocks are lost due to erosion/ folding, etc...
4. scientists that study fossils
5. a fossil that is widely distributed and and in existence for a relatively short period in geologic history. They are useful because they tell tell the relative age of the rock in which they are found.
7. the number of years that have passed since a rock formed
8. an extremely thin coating of carbon on rock - a fossil type
10. provides evidence of the activities of ancient organisms - a fossil type
11. a hollow area in sediment in the shape of an organism or part of an organism - a fossil type
13. a solid copy of the shape of an organism - a fossil type