1. Chapter 4: Views of Earth’s Past
Fossils

2. What is a Fossil? Traces/remains of living things from the past.
Give us clues about the past.
Exist in different forms.

3. Original Remains
Fossils that are the actual bodies of organisms; direct evidence of forms of life.
Found in places where conditions prevent decomposition.

4. Original Remains: Location
Ice: great preserver; mammoths and rhinos from 10,000 years were found.
Amber: comes from trees; holds insects and small creatures.
Tar: thick, oily liquid; saber-tooted cats were found.

5. Fossil Formation Soft body parts decompose quickly
Bones, shells, teeth, and tree trunks last longer.
Layers of sediment (sand and mud) form around these remains, created a fossil.
They can be destroyed if the rock changes.

6. Molds and Casts
Mold: a visible shape that was left after the remains decayed.
Cast: the minerals that fill the empty mold.

7. Petrified Wood The stone or fossil of a tree.
Minerals take the place of the tree and create a copy.

8. Carbon Films Carbon is an element found in all living things.
Sometimes the carbon creates a film that lasts after the rest decays.

9. Trace Fossils Preserved footprints, trails, animal holes, and feces.
Tells us where an animal lived, what they ate, and how they behaved.

10. Tree Rings Show a lot about past conditions, especially the weather.
If the rings are very thing, then it was probably a dry year because the tree did not grow much.
Thick rings indicate a rainy year.

11. Ice Cores
A tubular sample that shows the layer of ice and snow that have been piling up for thousands of years.
Show differences in weather patterns and natural disasters, such as volcanic eruptions.

12. Chapter 4: Views of Earth’s Past
Relative vs. Absolute Age

13. Relative Age
The age of an event or object in relation to other events or objects.
Example: I have an older brother. You know he is older than me, but not his exact age.

14. Relative Age
With sedimentary rocks, the oldest rocks are in the bottom layer and the youngest rocks are in the top layer.
Sometimes igneous rocks will melt into the layers that already exist. The igneous rock is younger.

15. Relative Age

16. Relative Age

17. Index Fossils
Fossils of organisms that were common, that lived in many years, and existed only in specific spans of time.

18. Index Fossils
We use them to help identify when other fossils were from.

19. Index Fossils

20. Absolute Age The actual age of an event of object.
Example: My older brother is 29 years old.