Geology 141
Autumn, 1999
Name
.
4 October, 1999
GE141: PHYSICAL GEOLOGY
FIRST HOUR EXAMINATION
INSTRUCTIONS:
Please read all instructions and questions
CAREFULLY and completely. If you do not understand a question
as it appears on the exam, PLEASE ASK FOR CLARIFICATION!!! It
is to YOUR benefit to do so. This examination is worth 100 points, or
10% of your overall semester grade. Exams will be graded as quickly
as possible; your individual point total will be entered on the last
page to ensure that only you know how well you did on the exam,
unless you choose to divulge that information to others.
"If you want to feel proud of
yourself, you've
got to do things you can be proud
of."
- Oseola McCarty (1908-1999)
Geology 141: Autumn, 1999
First Hour Exam
... Page 2 ...
Section I: Multiple choice. Please circle the letter of the response that is correct or that
BEST answers the question or completes the statement. There is ONLY ONE BEST
ANSWER for each question. Each question is worth 3 points; this section is worth 60 out
of the total of 100 for the exam.
PLEASE READ EACH QUESTION AND RESPONSE CAREFULLY !
1. The most abundant element in the Earth's crust, by weight as well as volume, is
a. silicon
c. iron
e. aluminum
b. oxygen
d. nickel
f. carbon
2. The "Big Bang" that created the known universe is believed by scientists to have
occurred
a. about 12-15 thousand years ago
d. about 4.5-5 thousand years ago
b. about 12-15 million years ago
e. about 4.5-5 million years ago
c. about 12-15 billion years ago
f. about 4.5-5 billion years ago
3. Our sun and solar system, including Earth, are believed to have formed
a. about 12-15,000 years ago
d. about 4.5-5 thousand years ago
b. about 12-15 million years ago
e. about 4.5-5 million years ago
c. about 12-15 billion years ago
f. about 4.5-5 billion years ago
4. Plate tectonics is ultimately driven by
a. the pushing and pulling of the Earth's plates by the tides.
b. slow movement of partially molten material in the aesthenosphere, driven by
heat produced by radioactive decay deep within the Earth.
c. the weight put on the Earth's crust by volcanism and the growth and melting of
great ice sheets during the Ice Ages.
d. flow within the liquid outer core around the solid inner core.
5. The west coast of South America is an area where
a. lithospheric plates are sliding past each other on a transform boundary.
b. lithospheric plates are pulling apart on a zone of divergence.
c. lithospheric plates are coming together in a zone of convergence.
d. there is almost no tectonic plate activity, since it's in the middle of a plate.
6. The major mineral groups are defined on the basis of their
a. internal structure c. mode of origin
b. chemistry
d. temperature and pressure stability fields
7. The only non-silicate mineral group that is more important as a rock-forming mineral
group than as an economic mineral group is the
a. feldspars
d. carbonates
b. sulfates
e. native elements
c. sulfides
f. oxides and hydroxides
8. Arguably the most important group of minerals, making up more than 50% of the crust
by themselves, are the
a. feldspars
d. carbonates
b. sulfates
e. native elements
c. sulfides
f. oxides and hydroxides
Geology 141: Autumn, 1999
First Hour Exam
... Page 3 ...
9. Magmas are
a. molten rock derived from the melting of pre-existing rocks.
b. chunks of rare rocks that show us what the mantle looks like.
c. molten rock derived from the outer core.
d. molten rock left over from the original formation of the Earth.
e. fragments of oceanic crust buckled up onto a continental margin.
10. As plutonic rock bodies, dikes are
a. tabular bodies, usually mafic, that cut across pre-existing rock units or layers.
b. tabular bodies, usually mafic, that were intruded in between older rock layers.
c. naturally occurring ridges along the coast of the Netherlands.
d. any intrusive rock body that occurs over a surface area of < 100 km2
11. Typical examples of shield volcanoes include all of the following except
a. Mauna Kea, Hawai'i
d. Olympus Mons, Mars
b. Mauna Loa, Hawai'i
e. Mt. Shasta, California
c. Kilauea, Hawai'i
f. Fernandina, Galapagos Islands
12. Porphyritic textures in igneous rocks, whether volcanic or plutonic, is the result of
a. slow cooling, allowing the phenocrysts to form, followed by more rapid cooling.
b. slow cooling that allows for magma fractionation, as seen in the Palisades Sill.
c. very rapid cooling, followed by more gradual cooling and absorption of water
by minerals like amphiboles and micas.
d. crystallization of minerals low in Bowen's Reaction Series, making the
remaining magma hotter.
13. All of the following things are true of the minerals at the top of Bowen's Reaction Series
EXCEPT
a. they have higher melting points than those at the bottom of the Series.
b. they have lower silica contents than those at the bottom of the Series.
c. they are more likely to be phenocrysts in volcanic rocks than those at the bottom
of the Series.
d. they are more stable at the Earth's surface temperatures and pressures than
minerals at the bottom of the Series.
14. Felsic magmas are more likely than mafic magmas to produce plutonic rocks because
a. felsic magmas originate much deeper within the Earth than mafic magmas.
b. felsic magmas are found everywhere, while mafic magmas are fairly rare.
c. felsic magmas are much more viscous than mafic magmas.
d. felsic magmas are always plutonic, mafic magmas always volcanic.
15. Most of the volcanoes in the world are
formed by
lavas. (Circle
the letter of the correct pair of words or phrases that properly complete this sentence)
a. shield volcanoes, felsic
d. stratovolcanoes, mafic
b. shield volcanoes, mafic
e. stratovolcanoes, intermediate
c. stratovolcanoes, felsic
16. You are part of a scientific team that has been working in central Borneo, and you've
found and mapped a previously unknown body of granite that outcrops over an area of
78 km2. A body of granitic rock this large would be called a
a. sill
c. batholith
e. xenolith
b. dike
d. stock
f. lithograph
Geology 141: Autumn, 1999
First Hour Exam
... Page 4 ...
17. Which of the following mechanical weathering processes is LEAST likely to be
operating in non-coastal Central Maine in modern times?
a. ice wedging
c. root wedging
b. exfoliation sheeting
d. salt wedging
18. The critical difference between chemical weathering and mechanical weathering is that
a. chemical weathering occurs in place, mechanical weathering happens while the
material is moving.
b. chemical weathering produces rocks, mechanical weathering produces
sediments.
c. chemical weathering changes the minerals present, while mechanical weathering
only produces smaller pieces of the same composition.
d. chemical weathering only affects minerals, while mechanical weathering only
affects rocks.
19. The critical difference between weathering and erosion is that
a. weathering happens in place, while erosion is removal of materials.
b. weathering is natural, while erosion is the result of human activities.
c. all weathering involves chemical changes in minerals, while erosion never does.
d. weathering only affects rocks, while erosion only affects soils.
20. Of the more than 20 elemental nutrients that plants need to derive from soils, the only
one that is not derived from the chemical weathering of minerals is
a. potassium c. sulfur
e. iron
g. magnesium
b. phosphorus
d. nitrogen
f. calcium
h. zinc
Geology 141: Autumn, 1999
First Hour Exam
... Page 5 ...
Section II: Short answers, fill-ins, etc. Please respond to each question in the most
appropriate fashion. Please make your responses concise and to the point, but thorough.
There should be ample space provided for an adequate response; PLEASE RESTRICT
YOUR RESPONSES TO THE SPACE PROVIDED. PLEASE ALSO write legibly; I
CANNOT give any credit for responses I can't read! The number of points for each
question is indicated in parentheses after the question; there are 40 points possible for
this entire section.
21. The three major factors that determine the viscosity of magmas are: (5 points: 2-2-1)
22. What, on Earth, is the physical evidence that most strongly indicates that ours is a
second-generation star system? HOW does this evidence argue for that origin? (10
points)
23. WHY, once generated, do magmas tend to rise within the Earth? (5 points)
Geology 141: Autumn, 1999
First Hour Exam
... Page 6 ...
24. Where, specifically, do mafic and felsic magmas originate? (5 points: 3-2)
MAFIC magmas originate in
FELSIC magmas originate in
25. WHY are dikes and sills most commonly mafic, rather than felsic, in character?
(5 points)
26. The soils that are created in any area are a result of interactions between five principal
factors. We used a shorthand formula, shown below, to describe this relationship.
What are each of the factors involved ? (5 points - 1 point each)
S = f { P, B, C, T, t }
P=
B=
C=
T=
t=
27. In describing hydrolysis as a chemical weathering process, we used a generalized
chemical equation to show the net effects of hydrolysis on a generalized silicate
mineral in a rock. Fill in the blanks below with the principal products of this process.
(5 points: 2-1-1-1)
Generic silicate + H2O -->
+
+
+
Geology 141: Autumn, 1999
First Hour Exam
... Page 7 ...
28. On the maps on the following page (the maps are printed back-to-back), locate precisely
each of the following localities or features. FOR SMALL FEATURES OR LOCALITIES,
use a sharp arrow drawn from your label to the feature, so there can be no doubt about
what you are labeling. (10 points, 1 point each)
All labels must be correctly spelled for credit!
[ Since all you have to do is copy the name from the list below! ]
On the map of the U.S. & Canada:
Oregon
Lake Ontario
Sierra Nevada
Missouri
Georgia
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On the map of the world:
Andes Mountains
Turkey
Taiwan
Mediterranean Sea
Montserrat (island)
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Grade on exam: __________________ out of 100 possible*.
* If this is below 70, please see me within the next week !!!
NOTE: After exams are graded, I will return your exam ONLY to you. It will not be
released to friends, roommates, your lab partner, or anyone else. This is to ensure
YOUR security and confidentiality.