# FOSSIL AND RELATIVE AGE STUDY GUIDE

```FOSSIL AND RELATIVE AGE STUDY GUIDE
1. My sister is 14 years old is an example of an _ABSOLUTE_ age because I have an exact, definite age.
2. My brother is older than my sister is an example of a __RELATIVE__ age because I am making a comparison. I do
not have an exact age of my brother.
3. What law states that in undisturbed rock layers, the oldest rocks are on the bottom and the youngest are on the
top? PRINCIPLE OF SUPERPOSITION
4. What are the TWO cross cutting features that we discussed? FAULTS AND INTRUSIONS
5. If I have an intrusion going through a layer, which must be older – the layer or the intrusion? How do you know?
THE LAYER MUST BE OLDER BECAUSE THE LAYER HAD TO BE THEIR FIRST IN ORDER FOR THE INTRUSION TO GO
THROUGH IT. AN INTRUSION CAN’T GO THROUGH A LAYER THAT DOESN’T EXIST.
6. What is contact metamorphism? THIS IS WHEN AN INTRUSION GOES THROUGH LAYERS, AND AS IT DOES, IT
“BAKES” THE ROCKS SURROUNDING THE INTRUSION (OR THE ROCKS THAT COME IN CONTACT WITH THE
INTRUSION) INTO METAMORPHIC ROCK BECAUSE OF ALL OF THE HEAT THAT IS COMING OFF OF THE INTRUSION
7. What is an unconformity? AN UNCONFORMITY IS A GAP IN THE LAYERS DUE TO EITHER: 1. LACK OF DEPOSITION
(SEDIMENT HAS NOT BEEN DEPOSITED FOR MANY, MANY YEARS) OR 2. A LOT OF EROSION HAS OCCURRED, TAKING
LAYERS OF SEDIMENTARY ROCK AWAY
8. List and DESCRIBE the THREE types of unconformities we discussed. Draw a picture of each.
NONCONFORMITY (REMEMBER:
DISCONFORMITY: new sediments are ANGULAR UNCONFORMITY: a new
NONE ARE THE SAME) this is when
deposited on top of very old
layer of sediments make a horizontal
new Sediments are deposited on top
sediments, and there is a LARGE gap
layer on top of old/angled layers
of eroded Igneous or Metamorphic
in time between the new and old
rock
layers
SEDIMENTARY
SEDIMENTARY
ERODED IGNEOUS OR
METAMORPHIC
OLD SEDIMENTARY ROCK
9. DRAW and LABEL the three types of Folds: Monoclines, Anticlines, and Synclines
ANTICLINE
MONOCLINE
SYNCLINE
10. __PALEONTOLOGISTS___ study fossils and reconstruct the appearance of animals.
11. What are fossils? the remains, imprints, or traces of a prehistoric organism
12. List and DESCRIBE, IN DETAIL, the FOUR types of Preservation.
1. MOLD AND CAST: Animals with shells or hard exoskeletons buried in sediments are often acted upon by acid-rich ground
water which may dissolve away shells or other organic structures. The void created by this action is called a mold. Sediments
then wash into the mold and create an almost exact replica of the original remain called a cast.
2. PERMINERALIZED: minerals from groundwater fill the pore spaces of an organism and crystallize creating a rock hard version
of the original organism
3. CARBON FILM: Elements in organic matter waste away, leaving a thin carbon film as the only fossil record. It looks like an
outline or a silhouette of the organism.
4. TRACE FOSSILS: Show the organism’s activities; for example, footprints and burrows.
5. ORIGINAL REMAINS (AMBER, ICE, AND TAR): organisms’ SOFT parts can be preserved in amber, ice, or tar. Insects are typically
preserved in amber.
13. What is an index fossil and how do scientists use them? AN INDEX FOSSIL CAN BE USED TO HELP SCIENTISTS WITH
ABSOLUTE AND RELATIVE DATING. TO BE AN INDEX FOSSIL, THE FOSSIL MUST BE:
A. ABUNDANT (LOTS OF THEM)
B. GEOGRAPHICALLY WIDESPREAD (FOUND ALL OF THE WORLD)
C. LIVE FOR A RELATIVELY SHORT PERIOD OF TIME
14. I found a fossil of a fly that is almost in its original form. What substance must this fly have been preserved in?
AMBER
15. What do trace fossils tell us and what is an example of a trace fossil? TRACE FOSSILS TELL US ABOUT AN
ORGANISM’S ACTIVITIES – WHAT WAS THE ORGANISM DOING? WHERE WAS IT GOING? WHO WAS IT TRAVELING
WITH? HOW FAST WAS IT GOING? ETC.
EXAMPLES: FOOTPRINTS AND BURROWS
16. If an organism no longer exists, it is said to be ____EXTINCT __. (Example: Dinosaurs)
CHALLENGE!
You have to at
least try it! Put
the layers in
order from
oldest to
youngest!
OLDEST:
YOUNGEST:
E
D
F
A
C
B
```