Name: ________________________
Interpreting Geologic History – Relative Dating
Rules & Guidelines:
1. Uniformitarianism – “The present is the key to the past”
2. Original Horizontality – Sedimentary rock units are deposited in horizontal
layers. Tilts, Folds, Faults all occur after deposition.
3. Superposition – Oldest rock units on the bottom, youngest rock units at the
surface. Sometimes faulting doesn’t affect superposition:
Sometime faulting does create exceptions to superposition:
4. Cross-Cutting – Rock units are older than whatever cuts through them.
5. Intrusions/Extrusions – Look to the rock unit above the igneous rock and ask
was it altered (metamorphosed) by the igneous rock?
6. Unconformities – buried erosional surface. Missing part of the rock record.
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Name: ________________________
Interpreting Geologic History – Relative Dating
Exercise A: The Basics
Write the sequence of events that led to these:
Unconformity
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Name: ________________________
Interpreting Geologic History – Relative Dating
Exercise B: Intrusions and Extrusions
1. What is the evidence from the
diagram to the right that the sandstone
in cross section A is older than the
igneous rock and the sandstone in cross
section B is younger than the igneous
rock?
2. Which is an intrusion and
which is an extrusion?
Use the following cross section from the Newark Lowlands (just on the far side of
the George Washington Bridge along the Palisades parkway) to answer the
following:
3. What is the evidence shown in the diagram above that the Palisade Sill was an intrusion?
(Do not write that the words igneous intrusion are written in parenthesis below it)
4. What is the evidence shown in the diagram that the Hammer Creek conglomerate was
formed after the Basalt flow.
5. Assume that no overturning has occurred. List the rock units in age order from
oldest to youngest.
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Name: ________________________
Interpreting Geologic History – Relative Dating
Exercise C: Practice regents questions:
1.
2.
3.
4.
5.
6.
7.
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Name: ________________________
Interpreting Geologic History – Relative Dating
8. Write the names of the rock units and events in
order from oldest to youngest that created the
profile to the left.
9. What two rock units identified by letter are the
same age? Why?
10. Put the letters in order from oldest to youngest.
11. Write all the events in order from oldest to youngest.
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Name: ________________________
Interpreting Geologic History – Relative Dating
12.
Write all the events that led to the geologic profile above.
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Name: ________________________
Interpreting Geologic History – Relative Dating
Exercise D: Answer the following questions about the Catskills:
Folding is often the cause of mountain/hilly terrain.
Occasionally, as in the Catskills of NY, elevated horizontal sedimentary rock units are
eroded to create the mountainous/hilly terrain.
Look to your ESRT and recall past lessons to answer the following:
1. What is the proper name for the landscape region of the Catskills?
2. Are they “true” mountains?
3. What erosional force created the valleys of the Catskills?
4. The sedimentary rocks of the Catskills are limestones, shales, sandstones, and
conglomerates. What do these rocks tell us about the past environment of the Catskill
region?
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Name: ________________________
Interpreting Geologic History – Relative Dating
Answer Sheet
Exercise A:
Profile A:
_____________________
Profile C:
______________________
_____________________
______________________
_____________________
______________________
_____________________
______________________
Profile B:
_____________________
Profile D:
______________________
_____________________
______________________
_____________________
______________________
_____________________
______________________
Profile E: (about 15 steps)
Profile F: (about 15 steps)
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Name: ________________________
Interpreting Geologic History – Relative Dating
Exercise B:
1. __________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
2. __________________________________________________________
__________________________________________________________
3. __________________________________________________________
__________________________________________________________
4. __________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
5. __________________
__________________
__________________
__________________
__________________
__________________
Exercise C:
1. __________________________________________________________
2. __________________________________________________________
3. __________________________________________________________
4. ___________________
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Name: ________________________
Interpreting Geologic History – Relative Dating
5. ___________________
6. ___________________
7. __________________________________________________________
8. ___________________
___________________
___________________
___________________
___________________
___________________
___________________
___________________
___________________
___________________
9. __________________________________________________________
10.__________________________________________________________
11.___________________
___________________
___________________
__________________
__________________
__________________
__________________
__________________
___________________
12. (about 15 steps)
Exercise D: Answer 1 – 4 on p. 7. Look to pages 8&9 of the ESRT when
you’re done to have a discussion on the geologic history of NY.
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