SAMPLE TEST

HOUR EXAMINATION #1
Geology 200: Processes and Concepts of Geology
February 18, 2000
(All Tests Due at 10:55 a.m.)

1. How are the seismic P-waves and S-waves used to discern that the Earth has a liquid outer core and a solid inner core? Please use a labeled diagram in your answer. [10 points]

2. How do the silicate structures of the minerals in the discontinuous sequence in Bowen's Reaction Series change with decreasing temperature of the magma? [5 points]

3. Identify, define and/or describe any three of the following terms. Be sure to include dates, examples and diagrams where appropriate. For each selected term, state its importance in geology. (If more than three are answered, only the first three will be graded.) [15 points]
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fractional crystallization

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sedimentary facies

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permineralization

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isochronous surface

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Walther’s law

4. You’ve seen this before. Fill in the blanks with the igneous rock names! [10 points]

Intrusive -->
Extrusive -->
Magma character --> “mafic” or “basic” “intermediate” “silicic” or “felsic”
Magma temps --> ~1200°C ~900°C ~700°C

 

5. Why do we have many basaltic eruptions at the Earth’s surface but relatively few silicic (or felsic) ones? [10 points]

6. You have collected two sediment samples along an ancient river bed. To establish which direction the river was flowing, you need to know which sample is the most mature. Your mineralogical analysis of the sediments shows the following:

SEDIMENT SAMPLE A SEDIMENT SAMPLE B
5% Pyroxene 55% Quartz
10% Amphibole 10% Magnetite
10% Biotite 10% Biotite
10% K-feldspar 5% Muscovite
15% Ca-Na Plagioclase 5% Ca-Na Plagioclase
40% Quartz 15% K-feldspar
5% Magnetite
5% Muscovite

Which sample is the most mature and why? [10 points]

7. You know what to do here. List the units and events (folding, erosion, intrusion, etc.) in their relative sequence order, placing the oldest at the bottom. Along with the sequence, label on the diagram any unconformities, giving them the proper names (disconformity, angular unconformity, or nonconformity). Unit A is a metamorphic rock. Unit B is an igneous intrusion. X-X’ is a fault; Y-Y’ is an erosional surface (but not the only one). [10 points]

8. How can decreasing the pressure on a rock (as in ascending movement through the crust) lead to melting of that rock? What kind of rock is most likely to do this? [10 points total]

9. Please list below and briefly describe the principle “agents of metamorphism”. In other words, what are the processes by which rocks are metamorphosed? [10 points total]

10. 14C (“carbon-14”) radioactively decays into 14N (“nitrogen-14”). Carbon has an atomic number of 6 and Nitrogen has an atomic number of 7. So, what type of radioactive decay (alpha, beta or electron capture) is featured in 14C --> 14N? What are the reasons for your decision? [10 points]