1. Earth’s past is revealed in rocks and fossils
Chapter 5.3

2. Fossils and original remains give clues about the past
Fossils are important clues about past events
These are traces or remains of living things from along ago

3. Types of Fossils Dinosaur footprint Dinosaur bones Petrified trees
Leaf impressions

4. Fossil formation Rock fossils form in sedimentary rock
If sedimentary rocks are changes by heat or pressure, their fossils can be destroyed

5. What are not fossils?
Arrowhead
Caribou skull
Amethyst crystal
Geode

6. How old are fossils?
The first common fossils come from the Cambrian period over 600 million years ago!
Phacobs, a common Trilobite fossil dates from 400 million years ago!!

7. Fossils in Rocks Molds and Casts Mineral Replacement Carbon Films
Trace Fossils

8. Molds and Casts
A mold is visible shape that was left after an animal or plant was buried in sediment and then decayed away
A cast fossil is a solid model in the shape of the organism

9. Mineral Replacement
Example is petrified wood or a stone fossil of a tree

10. Carbon Films Carbon is an element that is found in every living thing
Sometimes dead plant or animal decays leave a carbon behind as a visible layer

11. Trace Fossils
These are not parts of an animal or impressions, but rather an evidence of an animal’s presence
It includes preserved footprints, animal holes and even feces

12. Original Remains
Fossils that are the actual bodies or body parts of organisms
Types:
Ice
Amber
Tar

13. Ice
One of the best preservers. Huge ice fields in Siberia and North America contain bodies of mammoths and rhinos

14. Amber
A sticky substance inside trees called resin, flows like syrup and protects the tree by trapping insects

15. Tar A thick oily liquid called tar can also preserve remains
Saber-toothed cats and other animals were trapped in pools of tar and have been preserved for thousands of years

16. Ice Cores
These are cylindrical samples that show layers of snow and ice that have built up over thousands of years
Layers of ice serve as vertical timeline of part of Earth’s past

17. Tree Rings Tree rings are thin when growing conditions are poor.
A thick ring is sign of a good year for growth
Analyzing tree rings of old trees help scientists develop an accurate history of overall weather patterns over time.
Tree Rings

18. Finding the Age of Fossils
Relative dating and absolute dating are two ways of determining the age of rocks
Index fossils can help match layers of the same age from many different locations
By using combination of absolute and relative dating of rocks and fossils, scientists can figure out the Earth’s past.