1. How Earth’s Past is Revealed.
fossils
How Earth’s Past is Revealed.

2. Fossils Evidence of prehistoric life
Traces or remains of living things from long ago
Give important clues about Earth’s past

3. Types of fossils
Most fossils are hardened animal remains such as shells, bones, and teeth
Minerals replace the remains
Fossils leave impressions in rock
Soft parts of organisms can be preserved in ice, amber, or tar

4. Fossil formation Conditions have to be just right
Remains need to be preserved before decomposition
Preserved soft parts are more rare than hard parts
Most fossils form in Sedimentary Rock
As the sediment settles and forms layers, plant and animal remains can be preserved
Why would you not find fossils in Igneous Rock?

5. Fossils in Rock
Mold – a visible shape of an organisms remains left after it decays (like a shoe print in the sand)
Cast –a solid model in the shape of the organisms remains (if the shoe print was filled in with clay and it hardens into the shape of the shoeprint)

6. Fossils in rocks
Petrified Wood –minerals take the place of the cells and harden over time making the organism look like it turned to stone
Carbon Films –carbon can be found in every living thing, sometimes the carbon is the only thing left behind after the organism decays, can show details of soft parts missed in other types of fossils

7. Fossils in Rocks
Trace Fossils –evidence of an organisms presence in a location, not remains
Footprints
Trails
Animal holes
Feces (yes, this is poo!)

8. Ice cores
A tubular sample that shows the layers of snow and ice that have built up over thousands of years
Found in glaciers and the polar ice caps
Scientist analyze trapped air
Looks like bubbles in the ice
Can tell us about the atmosphere thousands of years ago
Dust or ash in the ice means volcanic eruptions
Ice layer thickness tells us about temperatures

9. Index fossils
Fossil Record – all the fossils that have been found since the study of fossils began
Index Fossils
Fossils that are unique to a specific time period
Remains of organisms that lived for a short period of time
Used to date rocks and other fossils

10. Quick check 1. What type of rock will you most likely find fossils?
Igneous
Metamorphic
Sedimentary
Intrusive

11. 2. Which part of an ancient reptile would you expect to see in a rock fossil? A. eye B. bone C. heart D. muscle

12. 3.Which type of fossil would be most likely to show the complete outline of a leaf? A. petrified wood B. cast fossil C. mold fossil D. carbon film

13. 4. Which type of fossil is used to help date the rocks and fossils found around it? A. index B. cast C. mold D. trace

14. 5. What do scientist study in ice cores to know about ancient atmospheric conditions? A. pollen B. dust C. ash D. air bubbles