First Hour Exam, Fall, 1995

Geology 141
Autumn, 1995
29 September, 1995
Please read all instructions and questions CAREFULLY and
completely. If you do not understand a question as it appears on the exam,
It is to YOUR benefit to do so. This
examination is worth 125 points, or 12.5% of your semester grade. Exams will be
graded as quickly as possible; your individual point total will be entered on the
last page to ensure your confidentiality.
Note that the space left behind a question should be
approximately that needed to properly respond thoroughly. A 2-inch space
should be understood to indicate that you need more than two words to
respond adequately to a given question!
"Those who can make you believe
absurdities can make you commit
- Voltaire
Geology 141: Fall, 1995
First Hour Exam
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Geology 141: Fall, 1995
First Hour Exam
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Section I: Multiple choice. Please circle the letter of the response that is
correct or that BEST answers the question or completes the statement.
Please read each question and possible response carefully. There is ONLY
ONE BEST ANSWER for each question. Each question is worth 3 points; this
section is worth 75 out of the total of 125 for the exam.
1. The most abundant two elements in the Earth's crust, by weight, are
a. iron and nickel
c. iron and silicon
b. oxygen and silicon
d. oxygen and silicon
2. The most abundant two elements in the Earth's core, by weight, are believed
to be
a. iron and nickel
c. iron and silicon
b. oxygen and silicon
d. oxygen and silicon
3. The Earth, and by inference our solar system, is believed by scientists to be
about how old?
a. about 15-25 billion years old, possibly as young as 8-10 billion years
b. about 15-25 million years old, possibly as young as 8-10 million years
c. about 4-5 billion years old
d. about 4-5 million years old
4. All minerals are grouped into major categories based on their
a. internal chemistry
c. arrangement of silica tetrahedra
b. usefulness to society
d. economic value
5. The one major group of non-silicate minerals that is more important as
a rock-forming mineral group than it is economically is the
a. sulfides
c. oxides and hydroxides
b. carbonates
d. phosphates and sulfates
6. Orthoclase, microcline and sanidine are all feldspars that have the
chemical formula KAlSi3O8. What makes them different is that
a. some occur naturally, at least one is probably synthetic (man-made).
b. they have different crystal structures.
c. at least one probably has no silica tetrahedra.
d. at least one is probably a non-silicate.
7. The silicate minerals as a group are divided into subgroups based on
a. the structural arrangement of the silica tetrahedra in the crystal
b. whether or not silica tetrahedra are present in the structure.
c. the various metallic cations (Fe, Mg, Ni, Ca, etc.) that are present in
the minerals.
d. whether the minerals are derived from igneous, sedimentary or
metamorphic rocks.
8. Magmas that ultimately cool to become igneous rocks are derived from
a. vast pools of underground molten rock left over from formation of the
b. melting of pre-existing rocks by heat, derived from friction and decay
of radioactive isotopes deep within the Earth.
Geology 141: Fall, 1995
First Hour Exam
c. melting of pre-existing rocks by heat created by volcanoes.
d. the molten material of the outer core.
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Geology 141: Fall, 1995
First Hour Exam
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9. Magmas that have a chemical composition of about 50% SiO2, will also
commonly have relatively high amounts of what elements?
a. calcium, iron and magnesium
c. aluminum and potassium
b. potassium and sodium
d. sodium and aluminum
10. The magma in question (9), above, if it emerges at the Earth's surface, will
form what kind of rock?
a. granite
c. basalt
b. felsite
d. andesite
11. If this same magma cooled underground, it would form a
a. gabbro or diabase
c. basalt
b. rhyolite
d. diorite
12. The magma referred to in the previous three questions would originate
a. in the continental crust, particularly the interiors of mountain ranges.
b. in the upper parts of volcanoes on continental margins.
c. in the upper mantle of the Earth.
d. by the chemical weathering of older rocks by heat and pressure.
13. The three principal factors that determine the viscosity of a magma include
all of the following except
a. temperature of the magma
c. dissolved gasses (especially water)
b. silica content of the magma d. age of the magma
14. Mount Lolly is underlain and surrounded by a distinctive granite that is
apparently massive, and is found over an area of 86 square kilometers.
An igneous intrusive rock body of this size is known as a
a. batholith
c. stock
b. dike
d. sill
15. Volcanoes are
a. the sites where magmas originate and come out of the Earth.
b. typically mountains built up of countless layers of volcanic flows and
pyroclastics, derived from magmas originating deep in the Earth.
c. giant hills or mountains that have been pushed up like a giant bubble,
by the pressure of magmas underneath.
d. steep-sided high mountains of any origin.
16. Explosive volcanic eruptions are most likely to occur when the magmas
that are involved are of what general character?
a. ultramafic
c. intermediate or felsic
b. mafic
d. very low viscosity
17. The most abundant igneous rock type in the entire world is
a. granite
c. rhyolite
b. basalt
d. andesite
18. Typical causes of mechanical weathering in rocks include all of the
following except
a. ice wedging
d. root wedging
b. hydrolysis
e. thermal expansion & contraction
c. salt crystal growth
Geology 141: Fall, 1995
First Hour Exam
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19. Acidic conditions generally assist chemical weathering processes because
a. most minerals are very soluble in even slightly acid conditions.
b. acid conditions are created when water molecules have a polar structure
(i.e., one "end" of the molecule is negatively charged, the other is
positively charged).
c. all chemical weathering processes require the interactions of acids
and minerals.
d. hydrogen ions are capable of displacing metallic cations (e.g., K+) in
mineral crystal structures.
20. Clay minerals originate by
a. ice-wedging of rocks in cold environments.
b. hydrolysis of feldspars (and other silicates).
c. solution of soluble minerals (e.g., gypsum, calcite) in water.
d. crystallization from low-temperature magmas.
21. Chemical weathering is all but impossible if the environment has no
a. variation in rock types
c. living organisms
b. water
d. temperature variation
22. The igneous rock that would be most susceptible to chemical weathering
processes, all other conditions being equal, would be a (an)
a. granite
c. rhyolite
b. olivine basalt
d. andesite
23. The soil horizon with the greatest rate of chemical weathering and the
greatest biological activity is the
a. A horizon
c. C horizon
b. B horizon
d. parent material
24. The difference between primary and secondary minerals in a soil is that
a. primary minerals are present in greater abundance than secondary
b. primary minerals are derived from the parent materials; secondary
minerals actually formed in the soil.
c. primary minerals are simpler in chemical composition than secondary
d. primary minerals are found in upper soil horizons; secondary minerals
are found in the lower soil horizons.
25. The only element that plants must get through their roots from soils that
is NOT provided by the chemical weathering of minerals is
a. iron
d. nitrogen
b. sulfur
e. potassium
c. phosphorus
f. calcium
Geology 141: Fall, 1995
First Hour Exam
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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 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 50 points possible for the entire
26. What are the critical differences between minerals and rocks? (10 points)
27. Fill in the blanks below with the names of each of the minerals that make
up Bowen's Reaction Series (10 points; 1 point for each answer plus 1
bonus point for making any serious attempt).
Geology 141: Fall, 1995
First Hour Exam
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Geology 141: Fall, 1995
First Hour Exam
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28. Name three major volcanoes in the world that are NOT shield volcanoes.
(5 points: 2-2-1)
29. (A) What is the critical difference between chemical and mechanical
weathering? (5 points)
(B) Give and briefly describe one example of each of these two major
categories of weathering. (5 points: 3-2)
30. In discussing soils, we identified five principal factors that are critical
in the development of any individual soil. We summarized these in a
simple equation, in which S represents the soil. Identify the five factors
that are critical in soil formation (5 points; 1 point for each factor)
the equation:
S = ƒ { P, C, B, T, t }
Geology 141: Fall, 1995
First Hour Exam
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31. On the maps on the following page (the maps are printed back-to-back),
locate precisely each of the following localities or features. WHEN IT IS
NECESSARY FOR CLARITY, use a sharp arrow drawn from your label to
the feature. (10 points, 1 point each)
All labels must be correctly spelled for credit!
On the map of the U.S.:
Gulf of California
Washington (state)
On the map of the world:
Red Sea
Andes Mountains
New Zealand
Grade on exam: __________________ out of 125 possible.
NOTE: After exams are graded, I will return your exam ONLY to you.
It will not be released to friends, roommates, lab partners, etc.