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Exam 2

Exam 2. Exam 2 will cover the Fourth Dimension and Plate Tectonics. You will only need a pen or pencil (calculator optional) There will be 50 questions (about 25 per sections). Format will be mult.choice/T-F with 3 extra credit fill in.

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Exam 2

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  1. Exam 2 • Exam 2 will cover the Fourth Dimension and Plate Tectonics. • You will only need a pen or pencil (calculator optional) • There will be 50 questions (about 25 per sections). • Format will be mult.choice/T-F with 3 extra credit fill in. • It would be to your benefit to use assignment 3 and 4 as a study guide!! • **The powerpoint is a guide to help with studying but please be aware unless we say it is NOT on the exam then it is fair game**

  2. Plate Tectonicshttp://www.brooklyncollegegeology.com/plates/platesindex.html • Know the different types of plate boundaries and what geologic features occur at those boundaries (e.g. , convergent, divergent, mountains, volcanoes) • Understand what geologic processes occur at each of the plate boundary types( e.g. , rifting, subduction) • Review how Wegner devised his theory of “continental drift”. • Understand how geologist investigate the interior of the Earth. • Know what the different layers of the Earth are. **You WILL NOT be asked to determine the epicenter, focus or magnitude of earthquakes.

  3. D C Example of what you would need to identify.

  4. The Fourth Dimension • Environments of Rock Formations: • Igneous Rocks • In a Lava flow • http://www.brooklyncollegegeology.com/fourth/volc_rollover/volc_rollovera.html • In a magma chamber • http://www.brooklyncollegegeology.com/fourth/crystallization_rollover/crystallization_rollover.html • -Understand the process igneous (volcanic) rocks undergo in a magma chamber and lava flow • -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?

  5. The Fourth Dimension Environments of Rock Formations: Metamorphic Rocks: ►Understand the process metamorphic rocks undergo when heat and pressure are applied http://www.brooklyncollegegeology.com/fourth/meta_rollover/meta_rollover.html Sedimentary Rocks: ► Lithification vs Cementation http://www.brooklyncollegegeology.com/fourth/diagen_rollover/diagen_rollover.html http://www.brooklyncollegegeology.com/fourth/cement_rollover/cement_rollover.html (Nothing on Salt water lakes or Hypersaline conditions)

  6. Determining Rock Origin Four Clues to determine a rocks origin: --Mineralogy of the rock: the minerals that the rock contains. --Texture of the rock: the sizes, shapes and arrangement of the grains. --Structure of the rock: larger scale features, such as layering or discontinuities. --Field relationships: the size and shape of the rock body and how it relates to other rock bodies. http://www.brooklyncollegegeology.com/fourth/rock_origin_determine.html

  7. Rock Mineralogy: Igneous Rocks ►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) Example Question: Based on chart (b), a rock with composition “Y” contains how much feldspar? Ans. 20 % http://www.brooklyncollegegeology.com/fourth/rock_comp_igneous.html

  8. Rock Mineralogy: Continued Review Sedimentary, Metamorphic and the conclusions sections. This information sets the groundwork for the following sections. Sedimentary : http://www.brooklyncollegegeology.com/fourth/rock_comp_sedimentary2.html Metamorphic: http://www.brooklyncollegegeology.com/fourth/rock_comp_metamorphic.html

  9. 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 • Specific terms to know: • Clastic (rocks) • Crystalline (rocks) • Glass (volcanic) Vesicular vs Non vesicular • http://www.brooklyncollegegeology.com/fourth/rock_texture.html

  10. Rock Structure Read and have an understanding of : Primary Structures Layering 1, 2 and other Primary Structures http://www.brooklyncollegegeology.com/fourth/layering1.html http://www.brooklyncollegegeology.com/fourth/layering2.html http://www.brooklyncollegegeology.com/fourth/useful_structures.html Secondary Structures -Be sure to review rollovers discussing deformation and plate tectonics. http://www.brooklyncollegegeology.com/fourth/secondary_structures.html http://www.brooklyncollegegeology.com/fourth/deformation_rollover/deformation_rollover.html

  11. 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://www.brooklyncollegegeology.com/fourth/slaty_cleavage.html • http://www.brooklyncollegegeology.com/fourth/slaty_cleavage_origin.html • Origin of Cross-Cutting Rock Bodies • --review and have an understanding • --What type of evidence will you find near alteration zones? • http://www.brooklyncollegegeology.com/fourth/cross_cutting.html • http://www.brooklyncollegegeology.com/fourth/froshlec8.html

  12. Field Relationships--continued Igneous Origin --review and have an understanding http://www.brooklyncollegegeology.com/fourth/lava_sill.html Metamorphic Origin --Review “scenarios” of plate tectonic examples and metamorphism http://www.brooklyncollegegeology.com/fourth/field_meta.html Sedimentary Origin --review and have an understanding http://www.brooklyncollegegeology.com/fourth/field_sed.html

  13. Rocks and Earth’s History: 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://www.brooklyncollegegeology.com/fourth/froshlec8.html

  14. 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.) http://www.brooklyncollegegeology.com/fourth/froshlec8.html --determine the age of a layer based on information given http://www.brooklyncollegegeology.com/fourth/froshlec10.html

  15. Absolute Age We are only testing you on Radiometric dating from this page BUT you should still read the other sections as it may help connect other topics from previous sections. Use the Radiometric dating supplement in the following slides as your study guide not the website!! **Understand the difference between absolute age and relative age. http://www.brooklyncollegegeology.com/fourth/froshlec9.html **You are not responsible for Other absolute age dating techniques or the science–creationist controversy.

  16. 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. Radiometric Dating

  17. 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 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 Dating

  18. Radiometric Dating 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 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)

  19. Radiometric Dating 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= 1:3 Line 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).

  20. 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 Dating 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: 105/7=15 Parent-daughter ratio is 1:15 Now we work out a table until we reach the 1:15 ratio.

  21. Radiometric Dating 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.

  22. Unfolding the Earth’s History The Doctrine of Uniformitarianism: http://www.brooklyncollegegeology.com/fourth/froshlec11.html

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