1. Paleontology The study of past life
Paleontologist – scientist who studies fossils and plants from past life and other recontructed past ecosystems, study traces left behind by animals and piece together the conditions under which fossils were formed.
Uniformitarianism – the idea that the same geologic processes shaping the Earth today have been at work throughout Earth’s history

2. Relative vs. Absolute Dating
I. Relative dating – determining whether an object or event is older or younger than other objects or events
A. Superposition
1. Older rocks are under
newer rock
2. Can only determine relative time

3. B. Geologic column is an ideal sequence of rock layers that contains all the known fossils and rock formations on Earth arranged from oldest to youngest.

4. II. Absolute Dating – the process of establishing the age of an object by determining the number of years it has existed. A. Radioactive decay – the process in which a radioactive isotope tends to break down into a stable isotope of the same element.

5. 1. Radioactive atom has an
unstable nucleus that decays
a. Radiation is given off
b. Decay is at a constant rate
c. Decay material is formed
d. Half-life is the amount of
time for ½ of the radioactive element to decay

6. 2. Radioactive carbon dating
a. C-14 is present in all
living things
b. Used to date remains
***** Earth has been dated at
4.6 billion years

7. Fossils
III. Fossils – the remains or physical evidence of an organism preserved by geological processes. A. Trace Fossil – a fossilized mark that is formed in soft sediment by the movement of an animal. B. Index Fossil – a fossil that is found in the rock layers of only one geologic age and that is used to establish the age of the rock

8. Measuring Geologic Time
IV. Geologic Time
A. Eras (largest divisions)
1. Precambrian – earliest,
4 billion years
2. Paleozoic – 345 million years
3. Mesozoic – 160 million years
4. Cenozoic – current, so far
65 million years

9. B. Eras are divided into
periods (except for Precambrian)
Cenozoic periods are divided
into epochs

10. V. Geologic Eras
A. Precambrian
1. Earth forms including
seas & mountains
2. Few fossils of jellyfish,
worms, bacteria, algae,
& fungi

11. Paleozoic – 6 periods
1. Invertebrates most common
a. Trilobites
b. Brachiopods
2. Vertebrates – fish and
amphibians
3. Plants – ferns and trees in
swampy areas

12. Trilobite

13. Trilobite

14. Trilobite

15. Brachiopods

16. Brachiopods

17. Brachiopods

18. Eryops
Eryops

19. Eryops

20. Eryops

21. Mesozoic – 3 periods
1. Pangaea began to break
apart
2. Cycads & conifers evolved
3. “Age of the Reptiles”
4. Dinosaurs became extinct

23. Tyrannosaurus rex

24. Cycads

25. Cenozoic – 2 periods
1. “Age of Mammals”
2. At least 4 ice ages