Fossils & Age Dating Study Guide Key
A. If the statement describes a fossil write down the type of fossilization described. If it is not a
fossil only write NOT A FOSSIL!
1. Bird tracks in the snow. NOT A FOSSIL
2. Shell-shaped mineral found in rock cavity Cast
3. Insect in amber from a pine tree. Preserved
4. Dinosaur tracks in rocks Trace
5. Sandstone showing ripple marks from water NOT A FOSSIL
6. Dinosaur leg bone containing quartz and minerals instead of regular calcium Petrified
7. Thin cavity in a rock showing where a shell has decayed Mold
8. Burrows of worms that lived millions of years ago Trace
9. Living pine tree more than 4,000 years old NOT A FOSSIL
10. Thin layer of carbon from the remains of a plant that lived thousands of years ago Carbon film
11. Arrowhead made thousands of years ago NOT A FOSSIL
B. Answer the following questions.
12. What must happen to a dead organism if a fossil is to form? Have hard body parts and must be
covered quickly by dirt and sediment.
13. What can you infer about finding a seashell fossil on a mountain?
It once was part of the ocean..the sea level dropped or plates shifting later created mountains
14. What are three things about Earth’s past scientists can learn from fossils?
How old the earth is, the past environments, and the past diversity
15. What 2 characteristics describe a good index fossil?
Wide spread (found in lots of places), lived for a brief amount of time
16. How is an index fossil useful?
They tell the relative ages of the rock layers in which they occur- must be widely distributed and represent
an organism that only existed briefly in time.
17. What is the difference between relative age and absolute age?
Relative age is the age compared to something else; absolute age is the specific age of something
18. What is the “Law of Superposition”?
The deepest rocks are the oldest and the youngest are on top
19. What are the “gaps” or missing layers of rock in from a section of rock called? unconformities
20. Which is older a fault line in rock layers or the rock layers? Explain your thinking. Rock Layers
21.
a.
b.
c.
d.
e.
C or A? why? C is deeper
C or B? why? C and B are the same layer; equal
The dark line or A? why? A: dark line cuts across letter A
D or the dark line? Why? Dark line; D cuts lines
D or C? why? C is a deep rock layer
2008-2009 Edwards
22. What form of fossilization would this be an example of? (look left)
Cast fossil of a dog!!
23.What type of fossilization is this? Describe the environment/habitat of this
past creature.
Mold or trace--- a wet, oceanic, marine type habitat (star fish)
24. A common cause of gaps in rock layers is erosion
25. The law of superposition states than an older rock is deeper than
younger rock.
Match the term with the correct description.
26.b. absolute age
a. time it takes for half of an isotope to breakdown
27.a. half-life
b. the specific age of something
28.c. radiometric dating
c. uses isotope to calculate the absolute age of a rock
29. What do you notice about ancient organisms compared to organisms found closer to present day?
Present day organisms are more complex/advanced .
30. Roughly, how old is the Earth? 4.6 billion years old
31. What is the difference between a geologic era and a geologic period?
Geologic era is larger than a geologic period- a period is a smaller unit of an era
32. What two periods is the Cenozoic era broken into?
Quaternary and Tertiary
33. What is the first, longest and least known section of time in Earth’s history?
Precambrian
34. What type of animals dominated the Paleozoic era? The nickname for this Era was what?
Fish, amphibians—“Age of Fishes”
35. What type of animal was the Mesozoic noted for? The nickname for this Era was what?
Reptiles, small birds, dinosaurs, small mammals- “Age of Reptiles”
36. What type of animal became common during the Cenozoic era? The nickname for this Era was what?
Mammals; Homo sapiens (humans)- “Age of Mammals”
2008-2009 Edwards