Final Review – part 1The 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.

Final Exam Review – Environments of Rock Formation

Igneous RocksIn a Lava flowhttp://academic.brooklyn.cuny.edu/geology/leveson/core/topics/rocks/crystallization_rollover/crystallization_rollover.html

In a magma chamberhttp://academic.brooklyn.cuny.edu/geology/leveson/core/topics/rocks/volc_rollover/volc_rollovera.html

--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?

Final Review--Environments of Rock Formation

► Understand the process sedimentary rocks undergo in a salt water lake environmenthttp://academic.brooklyn.cuny.edu/geology/leveson/core/topics/rocks/rocks_origin_intergrowth.html

http://academic.brooklyn.cuny.edu/geology/leveson/core/topics/rocks/salt_solution_rollover/salt_solution_rollover.html

►Understand the process igneous rocks undergo in a magma chamber and lava flowhttp://academic.brooklyn.cuny.edu/geology/leveson/core/topics/rocks/crystallization_rollover/crystallization_rollover.html

http://academic.brooklyn.cuny.edu/geology/leveson/core/topics/rocks/volc_rollover/volc_rollovera.html

►Understand the process metamorphic rocks undergo when heat and pressure are appliedhttp://academic.brooklyn.cuny.edu/geology/leveson/core/topics/rocks/meta_rollover/meta_rollover.html

Final Exam Review -- Mineral Assemblages

►You will be responsible to determine percentages of minerals using the mineralAssemblage Chart (a). ► Chart (b) is an example of how to read the mineral assemblage chart. See link for specific details.

(a)(b)

Mineral From To Length

Calcium rich feldspar

0% 20% 20%

Pyroxene 20% 38% 18%

Olivine 38% 100% 62%

TOTAL 100%http://academic.brooklyn.cuny.edu/geology/leveson/core/topics/rocks/rock_comp_igneous.htm

Example Question: Based on chart (b), a rock with composition “Y” contains how much feldspar?Ans. 20 %

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/geology/leveson/core/topics/rocks/rock_origin_determine.html

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

Final Exam Review – Field Relationships

Origin of Slaty CleavageEx. 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_cleavage_origin.html

Origin of Cross-Cutting Rock Bodies--review and have an understanding

Igneous Origin--review and have an understandinghttp://academic.brooklyn.cuny.edu/geology/leveson/core/topics/rocks/field_relationships/lava_sill.html

Metamorphic Origin--Review “scenarios” of plate tectonic examples and metamorphismhttp://academic.brooklyn.cuny.edu/geology/leveson/core/topics/rocks/field_relationships/field_meta.html

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.brooklyn.cuny.edu/geology/leveson/core/topics/time/froshlec8.html

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/leveson/core/topics/time/froshlec10.html

A supplement to Radiometric DatingA 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

Radiometric DatingRadiometric DatingFollow 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

1st:Distinguish 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 1:63 ratio parent-daughter ratio. By creating the table we can figure out how my half-lives or years it take to get the 1:63 parent-daughter ratio.

Radiometric DatingRadiometric Dating

Parent U-237 Daughter Pb-207Parent/ Daughter

ratioHalf life Time Elapsed

1 0 1:0 0 0

1/2 1/2 1:1 1 704

1/4 3/4 1:3 2 1408

1/8 7/8 1:7 3 2112

1/16 15/16 1:15 4 2816

1/32 31/32 1:31 5 3520

1/64 63/64 1:63 6 4224

Line 1: The table always begins with 1 parent and 0 daughter giving you a 1:0 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)

Half life of Uranium is 704 million years

Radiometric DatingRadiometric DatingParent U-235

Daughter Pb-207

Parent/ Daughter ratio

Half life Time Elapsed

1 0 1:0 0 0

1/2 1/2 1:1 1 704

1/4 3/4 1:3 2 1408

1/8 7/8 1:7 3 2112

1/16 15/16 1:15 4 2816

1/32 31/32 1:31 5 3520

1/64 63/64 1:63 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 (1:63).

Line 3: Parent= half of Line 2 (half of ½ = ¼)Line 3: Daughter = 1- ¼ = ¾ Line 3: Ratio= 1:3Line 3: Add 1 to the previous half life (1+1=2)Line 3: Time Elapsed= 704+704=1408

The ratio 1:63 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).

Radiometric DatingRadiometric Dating

1st Distinguish the parent from the daughter:Samples contains 7 trillion atoms of the Parent (radioactive element) C-14Sample 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: 105/7=15 Parent-daughter ratio is 1:15

Now we work out a table until we reach the 1:15 ratio.

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

Radiometric DatingRadiometric Dating

Parent C-14

Daughter N-14Parent/

Daughter ratioHalf life Time Elapsed

1 0 1:0 0 0

1/2 1/2 1:1 1 5730

1/4 3/4 1:3 2 11460

1/8 7/8 1:7 3 17190

1/16 15/16 1:15 4 22920

Following the procedure from the previous example you complete the table until you hit the parent-daughter ratio determined from your question (1:15)

We then noticed that to have a ratio of 1:15 4 half lives had passed equivalent to 22,920 years, so the bone is more or less that age.