Final Review

1
Final Review part 1 The Fourth Dimension
?Please focus on topics in mentioned in this
review. ?There will be approximately 25
questions on the Fourth Dimension
(mult.choice/T-F). ?It would be to your benefit
to use assignment 4 as a study guide!! ?We want
all of you to be prepared for the exam but DO NOT
OVER-STUDY.
2
Final Exam Review Environments of Rock Formation

• Igneous Rocks
• ?In a Lava flow
• http//academic.brooklyn.cuny.edu/geology/leveson/
  core/topics/rocks/crystallization_rollover/crystal
  lization_rollover.html
• In a magma chamber
• http//academic.brooklyn.cuny.edu/geology/leveson/
  core/topics/rocks/volc_rollover/volc_rollovera.htm
  l
• --When will you have finer grains rocks vs.
  coarser grain igneous rock?
• --How do rocks behave when heated in comparison
  when they are cold?
• --Difference between vesicular and non-vesicular
  and where are they found?

3
Final Review--Environments of Rock Formation
? Understand the process sedimentary rocks
undergo in a salt water lake environment http//ac
ademic.brooklyn.cuny.edu/geology/leveson/core/topi
cs/rocks/rocks_origin_intergrowth.html http//acad
emic.brooklyn.cuny.edu/geology/leveson/core/topics
/rocks/salt_solution_rollover/salt_solution_rollov
er.html
?Understand the process igneous rocks undergo in
a magma chamber and lava flow http//academic.broo
klyn.cuny.edu/geology/leveson/core/topics/rocks/cr
ystallization_rollover/crystallization_rollover.ht
ml http//academic.brooklyn.cuny.edu/geology/leves
on/core/topics/rocks/volc_rollover/volc_rollovera.
html
?Understand the process metamorphic rocks undergo
when heat and pressure are applied http//academic
.brooklyn.cuny.edu/geology/leveson/core/topics/roc
ks/meta_rollover/meta_rollover.html
4
Final Exam Review -- Mineral Assemblages
?You will be responsible to determine percentages
of minerals using the mineral Assemblage Chart
(a). ? Chart (b) is an example of how to read
the mineral assemblage chart. See link for
specific details.
(b)
(a)
Mineral From To Length
Calcium rich feldspar 0 20 20
Pyroxene 20 38 18
Olivine 38 100 62
TOTAL 100
Example Question Based on chart (b), a rock
with composition Y contains how much
feldspar? Ans. 20
http//academic.brooklyn.cuny.edu/geology/leveson/
core/topics/rocks/rock_comp_igneous.htm
5
Final Review--Determining Rock Origin
--Look at the mineralogy of the rock the
minerals that the rock contains. --Look at the
'texture' of the rock the sizes, shapes and
arrangement of the grains. --Look at the
'structure' of the rock larger scale features,
such as layering or discontinuities. --Look at
field relationships the size and shape of the
rock body and how it relates to other rock
bodies. http//academic.brooklyn.cuny.edu/geolog
y/leveson/core/topics/rocks/rock_origin_determine.
html
6
Final Review Rock Texture

• Understand the differences in the texture of
  igneous, metamorphic and sedimentary rocks.
• For example If a geologist finds in the field a
  rock with poorly sorted grains with a clastic
  texture what class of rock would it belong too?
• Answer sedimentary
• http//academic.brooklyn.cuny.edu/geology/leveson/
  core/topics/rocks/rock_texture/rock_texture.html

7
Final Exam Review Field Relationships

• Origin of Slaty Cleavage
• Ex. What can occur near the contact between an
  igneous intrusive body and sedimentary rock?
• Ex. What is the metamorphic equivalent of shale?
• http//academic.brooklyn.cuny.edu/geology/leveson/
  core/topics/rocks/field_relationships/slaty_cleava
  ge_origin.html
• ?Origin of Cross-Cutting Rock Bodies
• --review and have an understanding
• Igneous Origin
• --review and have an understanding
• http//academic.brooklyn.cuny.edu/geology/leveson/
  core/topics/rocks/field_relationships/lava_sill.ht
  ml
• ?Metamorphic Origin
• --Review scenarios of plate tectonic examples
  and metamorphism
• http//academic.brooklyn.cuny.edu/geology/leveson/
  core/topics/rocks/field_relationships/field_meta.h
  tml

8
Final Exam Review Relative Age
? Know the definition and understand the
differences between each of these concepts LAW OF
SUPERPOSITION LAW OF LATERAL CONTINUTIY LAW OF
CROSS-CUTTING RELATIONSHIPS LAW OF ORIGINAL
HORIZONTALITY THE LAW OF BIOTAL SUCCESSION THE
USE OF PRIMARY STRUCTURES --How could you
determine the top side of a rock vs. the bottom
side using primary structures? http//academic.b
rooklyn.cuny.edu/geology/leveson/core/topics/time/
froshlec8.html
9
DECIPHERING A SAMPLE OF EARTH HISTORY
You will be given an example very similar to this
and have to determine --the sequence of events
--appropriate law (ex. The relative age of
Intrusion C and fault F-F can be determined by?
Ans. Cross-cutting relationships.) --determine
the age of a layer based on information
given http//academic.brooklyn.cuny.edu/geology/le
veson/core/topics/time/froshlec10.html
10
A supplement to Radiometric Dating
When calculating the age of a rock using
radiometric dating we can create a table to
better see the incremental changes between the
parent-daughter ratio. This is an explanation
of the construction of the table presented from
the website. On the exam you will be responsible
to answer 4 questions in regards to radiometric
dating by filling in blank portions of the
chart. http//academic.brooklyn.cuny.edu/geology
/leveson/core/topics/time/froshlec9.html

11
Radiometric Dating
Follow this example After careful analysis, a
geochronologist determines that an unweathered,
unmetamorphosed mineral sample contains 8
trillion atoms of the radioactive element U-235
and 504 trillion atoms of its decay product
Pb-207. Half life of Uranium is 704 million
years 1stDistinguish the parent from the
daughter Samples contains 8 trillion atoms of
the Parent (radioactive element) U-235 Sample
contains 504 trillion atoms of the daughter
(decay product) Pb-207 2nd Determine the
parent/daughter ratio. Divide the number of
daughter atoms over the number of parent atoms to
get the following 504/8 63 So for every 1
parent atom we have 63 daughter atoms giving us a
163 ratio parent-daughter ratio. By creating the
table we can figure out how my half-lives or
years it take to get the 163 parent-daughter
ratio.
12
Radiometric Dating
Parent U-237 Daughter Pb-207 Parent/ Daughter ratio Half life Time Elapsed
1 0 10 0 0
1/2 1/2 11 1 704
1/4 3/4 13 2 1408
1/8 7/8 17 3 2112
1/16 15/16 115 4 2816
1/32 31/32 131 5 3520
1/64 63/64 163 6 4224
Remember our goal is to get to this ratio
Half life of Uranium is 704 million years
Line 1 The table always begins with 1 parent
and 0 daughter giving you a 10 ratio. Line 2
Next take HALF of the parent from previous line
(half of 1 is ½). The numerator will give you the
parent portion of the ratio (which will always be
1). Line 2 Then to get the daughter portion
complete the fraction to equal 1 ( ½ ½ 1). The
numerator of the daughter fraction will give you
the second half of the parent-daughter
ratio. Line 2 This means 1 half life has
occurred. Line 2 Time Elapsed is increased by
the years of the half life (in our case is 704
million years)
13
Radiometric Dating
Parent U-235 Daughter Pb-207 Parent/ Daughter ratio Half life Time Elapsed
1 0 10 0 0
1/2 1/2 11 1 704
1/4 3/4 13 2 1408
1/8 7/8 17 3 2112
1/16 15/16 115 4 2816
1/32 31/32 131 5 3520
1/64 63/64 163 6 4224
Repeat the procedure described in the previous
slide to complete the table until you have
reached the ratio you determined in the initial
question (163).
Line 3 Parent half of Line 2 (half of ½
¼) Line 3 Daughter 1- ¼ ¾ Line 3 Ratio
13 Line 3 Add 1 to the previous half life
(112) Line 3 Time Elapsed 7047041408
The ratio 163 tell us that 6 half lives have
passed corresponding to 4224 million years or 4.2
billion years. (Remember that a million has 6
places, and billions has 9).
14
Radiometric Dating
Example 2 A piece of bone contains 7 trillion
atoms of Carbon 14 and 105 trillion atoms of its
decay product Nitrogen 14. Half life of Carbon
is 5,730 years
1st Distinguish the parent from the
daughter Samples contains 7 trillion atoms of
the Parent (radioactive element) C-14 Sample
contains 105 trillion atoms of the daughter
(decay product) N-17 2nd Determine the
parent/daughter ratio Divide the number of
daughter atoms over the number of parent atoms to
get the following 105/715 Parent-daughter ratio
is 115
Now we work out a table until we reach the 115
ratio.
15
Radiometric Dating
Parent C-14 Daughter N-14 Parent/ Daughter ratio Half life Time Elapsed
1 0 10 0 0
1/2 1/2 11 1 5730
1/4 3/4 13 2 11460
1/8 7/8 17 3 17190
1/16 15/16 115 4 22920
Following the procedure from the previous example
you complete the table until you hit the
parent-daughter ratio determined from your
question (115) We then noticed that to have a
ratio of 115 4 half lives had passed equivalent
to 22,920 years, so the bone is more or less that
age.