5. Fossils

6. Fossil are the preserved remains or traces of living things.
They form when living things die and are buried by sediment.
They are usually found in _______________ rock

7. 3 Main Types of Fossils 2. Molds and Casts:
1. Petrified fossils: formed by replacement.
Water carrying minerals replace all or part of an organism.
2. Molds and Casts:
Mold: hollow area in sediment in the shape of an organism
Cast: water carrying minerals seeps into the mold and deposits the minerals

8. 3. Carbon films: As a buried plant or animal decays, it releases gases containing carbon.
- the gases escape, leaving the carbon behind preserving the plant or animals image.

9. Trace fossils: evidence that an organism was previously there
Example: footprints, trails, burrows

10. Why do we study fossils?
1. The fossil record provides evidence about the history of life on Earth.
The fossil record can tell us about past environments and climate change on Earth.
The fossil record can tell us about mass extinctions

11. 2. The fossil record shows how organisms have changed over time
2. The fossil record shows how organisms have changed over time. (evolution)
It shows how organisms have gone from simple to more complex organisms

12. When rocks are rearranged by bending this is known as a :
A. fault
B. uplift
C. fold
D. I don’t know

13. Identify the type of fault shown in the diagram.
A. normal
B. reverse
C. strike-slip
D. I don’t know

14. Identify the force which caused the pictured fault.
A. tension
B. compression
C. shear
D. I don’t know

15. Define the following: Relative age Absolute age Law of superposition
Extrusions
Intrusions
Unconformity
Index fossil

16. Age of Rocks
Relative age: the age a rock compared the age of surrounding rocks
Absolute age: the age of a rock since it was formed
Law of Superposition: in horizontal rock layers, the oldest is always on the bottom.

17. - unconformity: a gap in the geologic record
- extrusions: lava that hardens on the surface
- always younger than the layer below it
- intrusions: magma that hardens below ground
- dike: always younger than the rock layer it
cuts across
- unconformity: a gap in the geologic record
- missing layer(s) usually due to erosion

18. -index fossil: a fossil that can be used to determine the relative age of rock layers
- fossil must be widely distributed and should
have existed for a short period of time.
Fossils record shows how life has become more complex.
Example : trilobites, ammonites

19. The Law of Superposition states that:
A. rock layers are deposited horizontally.
B. rock layers on the bottom are the oldest.
C. rock layers on the top are the oldest.
D. I don’t know

20. By studying fossils we can find out:
A. when extinct organisms lived
B. what extinct organisms behaved like
C. the year they died
D. I don’t know