Physical Geology (Geol 117) - Exam 1 - Fall 99 Inquisitor - H.D. Maher, Jr.

This is a practice exam from Fall of 99. The actual exam will have the same format, but will naturally not cover the exact same material. My suggestion is to go through this exam after you have studied the material in order to identify portions of the material covered that you might want to study more. From year to year the exact content of the course varies a bit. There may be a question or two asked in this test which we did not study . Hwever, most of the material should look familiar.


Matching (choose best fit, 2 points each)
1. ____ falsification ..........A) preserved gas bubbles in volcanic rocks or shallow intrusives
2. ____ natural theology ...B) classic hot spot site of volcanism, primarily basalts
3. ____ cleavage ................C) Columbia River flood basalts are an example, unusual large igneous event
4. ____ carbonates ............D) refers to change in composition of rock during metamorphism, open system
5. _____ sulfides ..............E) submarine hotsprings found at spreading ridges spewing sulfides
6. _____ vesicles ..............F) mineral that grows in fixed P-T conditions, e.g. sillimanite, kyanite
7. _____ LIP ....................G) a mineral group that includes galena, and which is oftenof economic importance
8. _____ Mt. St. Helens ...H) idea that disproving ideas is a critical part of the scientific process
9. _____ Hawaii ...............I) submarine debris flow that produces graded layers, punctuated sedimentation
10. ____ sorting ...............J) sediment trait describing variation in grain size, function of transport mechanism
11. ____ lithification ........K) attempt in 1600-1800s to find religious insight in workings of the natural world
12. ____ turbidite .............L) example of arc- subduction zone related volcanism
13. ____ index mineral .....M) mineral property reflecting atomic architecture & anisotropic bond strength
14. ____ metasomatism ....N) a mineral group that includes calcite, and which makes up a good bit of Florida
15. ____ black smokers ....O) digital reunification of clastic elements post catastrophic dislocation
...........................................P) process whereby sediment is transformed into sedimentary rock

Mixed format questions. Read carefully and answer the best you can. Partial credit given.


1) Define paradigm: (3 pts.)

 

Extra credit: List the four components of a scientific community as defined by Thomas Kuhn. (2 pts.)

2) Define mineral: (4 pts.)

 

Why is ice in your freezer technically not a mineral while ice in a glacier is? (1 pt.)

 

3) For the formula below put a box around the silicate structural component, a circle around the glue, and double underline the solid substitution series.


Ca (Mg, Fe) (SiO3)2


Is this a sheet, single-chain, double chain, or framework silicate (circle the right one)? Is it a mafic or sialic mineral (circle your choice)? (4 pts.)

4) In this depiction of an ionic group identify the silicate ion and the oxygen ion by filling in the blanks. Write the chemical formula for this group, including charge? ____________ . When linked to other similar ionic groups, what element is shared? ____________ Finally, briefly describe why this ionic group is important. (4 pts.)


5) What non-silicate mineral group is often of hydrothermal origin and an important economic resource: _____________________. What non-silicate mineral group forms in environments were evaporation is greater than precipiation? __________________________ What non-silicate mineral group is represented by rust? _____________________. (3 pts.)

6) An igneous rock that is so fine grained that minerals can't be identified in hand-specimen has a ___________________ texture, and crystallized relatively _________________ and is known as a ______________________ rock, because it is inferred to have once been a lava. In contrast a coarse grained igneous rock has a _____________________ texture, and is inferred to have crystallized relatively ______________________. These rocks formed by crystallizing from a magma and are known as ______________________ rocks. An especially coarse grained igneous rock known as a _________________ is thought to have had an unusually high __________ content allowing for the large crystals to grow. (4 pts.)
Bonus: On what time scales do the two types of igneous rocks form? (2 pts.)

7) Below is Bowen's reaction series. Use it to answer the following questions. Label the low temperature and high temperature ends. Label which end represents the minerals typical of continental crust, and which of oceanic crust.Circle the minerals that you might expect to find as phenocrysts in an andesite. Double underline the part which shield volcanoes would most likely be associated with, and single underline the part which stratovolcanoes would most likely be associated with. (4 pts.)


olivine -> pyroxene -> hornblende -> biotite -> K-feldspar, muscovite, quartz
Calcium-rich plagioclase -------------------------------> Sodium rich plagioclase

8) On the graph below three paths are shown for partially melting a rock. Which one might be important for the Andes? _______ Which one characterizes ascending mantle rock under Hawaii? ________ Which characterizes a melting glacier? _________ Which one characterizes friction, but seems to produce only very small amounts of melts? ___________ (4 pts.)


9) On the diagram which letter best represents the stock _____, the sill ______, the dike, the xenoliths ______, and the contact aureole ________. ( 4 pts.)

10) List three sedimentary transport agents. For each one indicate whether they move sediment in suspension or as bedload (traction deposits) or both. (3 pts.)


a) agent _____________________________ suspension/bedload? __________________________


b) agent _____________________________ suspension/bedload? __________________________


c) agent _____________________________ suspension/bedload? __________________________

11) Use the diagram below of stratigraphic columns and the associated information to answer the following questions. (5 pts.)
A - organic rich fine-grained muds, with occasional crawling trace fossils. ________________________
B - limestone breccias and boundstone composed of coral and algal material. ________________________
C - evaporites and thin muds with bird tracks and mud cracks ________________________
D - very well sorted sandstones with very large cross beds, and insect and ________________________
lizard tracks on the cross beds
For each sedimentary facies (A-D) propose a depositional evironment in the space provided to the right.


Is this a history of regression or transgression (circle the appropriate one)?


In which direction was the shoreline moving?


If a major global glaciation were to rapidly develop at the time represented by the top of the sections, which sedimentary facies (A-D) would likely be found above the facies A (this is a thought question)?


12)
Draw a cross section of a current ripple mark and of an oscillation ripple mark. Briefly describe what information they give about the conditions of deposition. (3 pts.)

 

 

 

 

 

 

13) The difference between a sandstone and a conglomerate is mainly in ___________ ______________ while the difference between a breccia and a conglomerate is mainly in ____________ ________. Evaporites form by the process of ________________________________, while most (but not all) limestones form by ______________________ processes. (3 pts.)


14)
List 4 of the many factors that influence metamorphism and the type of rock produced. (4 pts.)
a) _________________________________ b) ___________________________________
c) _________________________________ d) ___________________________________

15) List three geologic processes that cause a rock to travel to new P and T conditions and undergo metamorphism. Put a P next to it if it is associated with a prograde path and an R if retrograde. (4 pts.)

a) _____________________________ b) ________________________ c) ______________________

16) List two sources of heat that produce the present geothermal gradient. (3 pts.)


a) b)


What is a typical geothermal gradient for continental crust? _________ C°/km

17) Use the diagram below of P-T space and with metamorphic facies below draw in a path with a higher geothermal gradient, and path with a lower geothermal gradient, consistent with formation in a paired metamorphic belt. Which is most consistent with formation nearest to the subduction zone, which one is most consistent with formation beneath an arc? Which one is therefore most likely associated with granitic batholiths? Finally where do we see such a paired metamorphic belt? (4 pts.)

18) The diagram above and to the right is of a hydrothermal circulation cell. Designate with an A the areas where ions are be scavenged from the rocks with temperature increase, with B the area where hydrothermal minerals are precipitating due to decreasing temperature and reactions with wall rock, and with C the locality where precipitation is due to fluid mixing and temperature decrease. Mark with D, the likely source of heat driving the hydrothermal circulation cell. Finally, briefly explain why the hydrothermal fluids ascend where they do. (5 pts.)



19) List two specific ways in which the 'rock cycle' can be made an open system that evolves; i.e. ways that material is taken out of the system or new material introduced into the system (4 pts.).

a)

b)

20) There is often something you studied that was not asked on the test. Create your own question on material covered in this course, but not asked about in this test yet. This is not a bonus question - you should make an attempt some response. Points will be awarded based on the insight provided by and appropriateness of the question. (4 pts.)