Exam 1 Flashcards
(155 cards)
1
Q
What event unleashed a storm of solar wind that blew all remaining volatile elements away from the inner planets?
A
The onset of nuclear fusion in the sun
2
Q
The nebula that formed the solar system consisted of what kinds of material?
A
Mostly gas with a few pieces of solid dust.
3
Q
Why do the inner (“terrestrial”) planets generally lack H and He?
A
The inner planets were too hot to allow the condensation of these phases.
4
Q
Which answer correctly ranks planetary material, from the smallest to largest?
A
dust<planetesimals<planets
5
Q
What is the age of the Earth, in billions of years?
A
Between 4.5 and 4.65
(4.5)
6
Q
What is the main reason Earth’s temperature increased during its formation?
A
During collisions, kinetic energy was converted to heat energy
7
Q
All theories for the differentiation of Earth require what processes?
A
*Complete or partial melting
*Floating of a less-dense phase to the surface
*Sinking of a denser phase to the mantle
8
Q
During differentiation, the Earth’s core formed by what process?
A
Dense Fe-rich liquid sank to the center of the Earth
9
Q
Meteorites form when ___________
A
planetary bodies disintegrate when they collide with another object
10
Q
Compared to the bodies that produced stony meteorites, the planetary bodies that produced carbonaceous chondrite meteorties were ________
A
*cooler
*smaller
11
Q
Why does accretion accelerate during planet formation?
A
As planets get more massive, their gravitional pull increases, drawing more matter towards them
12
Q
Which of the following statements is TRUE?
A
Ultramafic rocks contain more Fe than intermediate rocks
13
Q
What is the composition of the following rock?
Oxide. wt%
SiO2. 71
TiO2 0.2
Al2O3. 14
CaO. 1.6
FeO. 1.9
K2O 4.6
MgO 0.4
Na2O 3.9
P2O5 0.07
A
felsic
14
Q
Of the common rock-forming elements, the heaviest is Fe. Rocks that contain abundant Fe tend to have high density, while rocks that lack Fe tend to have low density. Consider the following four igneous rocks. Which one do you think is the densest?
*Peridotite–ultramafic rock
*Basalt–mafic rock
*Diorite–intermediate rock
*Granite–felsic rock
A
Peridotite
15
Q
In addition to making the rocks dense, Fe also makes rocks dark in color. Consider the following three rocks:
*check M1.3 for colors
Which of the following statements is most likely true?
A
Rock B is more mafic than rock A
16
Q
The ocean floor is almost entirely covered by the rock basalt, an igneous rock that is mafic in composition. Which of the following statements must therefore be correct?
A
The average concentration of SiO2 of ocean floor rock is 50 wt%
17
Q
The composition of the Earth’s core is: __________
A
mostly Fe metal
18
Q
How does a xenolith get to the surface?
A
It is carried by magma
19
Q
A magma produced by partial melting has an intermediate composition. What must be the composition of the rock that melted to produce the magma?
A
It must have a mafic composition
20
Q
The S-wave velocity of a liquid is
A
zero
21
Q
Which of the following meteorites derive from an undifferentiated planetary object that disintegrated?
A
Carbonaceous chondrite meteorites
22
Q
For which of these layers of Earth are seismic waves useful for determining composition?
A
*mantle
*continental crust
*oceanic crust
23
Q
What layers of Earth are exposed at ophiolites?
A
*mantle
*oceanic crust
24
Q
The composition of the mantle can be inferred from the composition of magmas derived from partial melting of the mantle, which are always ____________
A
mafic
25
Where can geologist directly examine rocks from Earth's oceanic crust?
*at ophiolites
*check M2.2
26
What happens to seismic wave velocities across the moho?
They suddenly increase as you go down
27
How can geologists observe rocks from Earth's crust that are formed deep beneath the surface?
*they can examine rocks brought to the surface along faults
*they can examine rocks seen in deep boreholes
*they can examine xenoliths
28
How can stony meteorites be used to infer the composition of the mantle?
Stony meteorites represent the mantles of Earth-like planetary bodies
29
Which of the following statements are TRUE about the composition of the Earth's core?
*the core's composition cannot be described with the terms, "ultramafic", "mafic", "intermediate", or "felsic"
*the core has a metallic composition
*the composition of the core must be inferred since geologists have no access to actual samples of the core
30
Which of the following is NOT useful for inferring the composition of the core?
Xenoliths
31
Which statement is TRUE about the density of the core?
32
The Earth's core cannot be observed directly, but is assumed to be similar in composition to: _________
iron meteorites
33
To produce a magnetic field, the Earth's core must have which of the following properties?
34
Rank the desnity of the core, mantle, and bulk Earth:
From largest density to smallest: Core > Bulk Earth > Mantle
35
What properties of the core are needed in order that the Earth have a magnetic field?
*The material must be able to flow
*The material must conduct electricity
36
What is the main reason Wegener's theory wasn't accepted?
Wegener envisioned this motion being accommodated by the rotation of the earth creating a centrifugal force towards the equator. He believed that Pangaea was near the South pole and the centrifugal force of earth caused the protocontinent to break apart. This resulted in continents to drift towards the equator, which he deemed as "pole-fleeing." This idea for the mechanism of continental drift was rejected by the scientific community, due to actual forces generated by the rotation of the earth were calculated to be insufficient enough to move continents
37
What is the thicknessof the crust of the oceans?
7 km
38
What is the thickness of the lithosphere at the oceans?
100 km
39
What is the thickness of the lithosphere of the continents?
200 km
40
What is the thickness of the crust of the continents?
35 km
41
What is the boundary between the crust and mantle called?
MOHO
42
What is the composition of the mantle?
ultramafic
43
What is the composition of the oceanic crust?
mafic
44
What is the composition of the continental crust?
intermediate
45
How have geologists located the boundary (between the lithosphere and asthenosphere)? What tools did they use? What observations are best fit with the presence of this boundary?
Geologists located this boundary between the lithosphere and asthenosphere by studying the arrivals of earthquakes, this allows them to determine the seismic wave velocities at various depths. Seismic wave velocities are dependent on the material's composition, temperature, and pressure
To identify the boundary, geologists used seismic wave velocities. Typically, seismic wave velocities beneath the oceans increase in a predictable manner down to a depth of about 100 kilometers, where they begin to decrease. This decrease in the seismic wave velocity allowed geologists to infer that the reason for the low velocity (especially at this depth) is that the rock contains a small percentage of liquid. Rocks with a few percent of liquid have low viscotiy and can flow, this is the asthenosphere.
Seismic wave velocities also depend on the type of material. Rocks made up of rigid material will have a high seismic wave velocity and rocks made up of less rigid material have lower seismic wave velocities. The lithosphere was found to have high P-wave velocities and the asthenosphere was found to have low P-wave velocities, indicating a change in rigidity.
46
As noted in the table, the "gooey" fluid asthenosphere has a density of approximately 3,320 kg/m3. Based on your calculations, will the oceanic lithosphere "float" or "sink" into the asthenosphere?
sink
47
As noted in the table, the "gooey" fluid asthenosphere has a density of approximately 3,320 kg/m3. Based on your calculations, will the continental lithosphere "float" or "sink" into the asthenosphere?
float
48
How deep do subducted plates actually go?
660 km deep
49
Do you think the boundary between the lithosphere and asthenosphere represents a surface of constant pressure or temperature?
The boundary between the lithosphere and the asthenosphere represents a surface of constant temperature. I came to this conclusion, because the lithosphere consists of two compositional layers: entire crust (upper part) and the uppermost part of the mantle (lower part). Beneath the lithosphere there lies flowing rock with mantle composition. The uppermost part of this is the asthenosphere. The asthenosphere consists of the same composition as the "lithospheric mantle" but is hotter and softer.
As we go into the Earth, both the temperatures and pressure increase, and these changes have opposite effects on rigidity. Increasing pressure makes rocks less rigid. The lithosphere is rigid, whereas the asthenosphere is less rigid. This makes me further believe that the boundary represents constant temperature.
Seismic wave velocities also decrease with increasing temperature, which means rocks are less rigid. Geologists have found that the lithosphere consists of a higher P-wave velocity compared to the asthenosphere. Meaning the boundary is a surface of constant temperature.
50
Which of the following statements is TRUE about the Theory of Continental Drift?
The Theory of Continental Drift was abandoned because its proponents could not explain how continents could drift
50
Your weighted average density calculation demonstrated something very important to plate tectonics. Based on your results, why don't continental plates subduct like oceanic plates?
Based on my results, continental plates do not subduct like oceanic plates because the oceanic plate is denser than the continental plate. Oceanic plates are primarily composed of basalt, meaning mafic rock. Continental plates are primarily composed of intermediate rock. Since the continental plate is composed of intermediate rock, it is too buoyant to be forced downward or be subducted. If it were to collide with a continent, it would simply crumple and stay at the surface.
50
The Theory of Plate Tectonics emerged in the 1950's following a period of intense exploration of the seafloor. Prior to this time, almost nothing was known about the seafloor. Why do you think the seafloor was the key to developing the Theory of Plate Tectonics?
Before the Theory of Plate Tectonics had emerged, Wegner had proposed a mechanism for continental drifting: the Pangea began near the south pole and the centrifugal force of the planet caused Pangea to break apart into continents that drifted towards the equator (pole-fleeing). This idea was rejected by the scientific community, because it did not align with the calculations of the forces generated by earth's rotation.
During the 1950s, people started to study and map the ocean floor. This exploration allowed samples to be taken from the ocean floor. These rocks provided more information about the composition of the rocks and their distribution. By analyzing the rocks, the scientists discovered that the age of the rocks increased as they move away from the mid-ocean ridge, also known as "seafloor spreading." Seafloor spreading is the process in which the seafloor splits and moves along a mid-ocean ridge and new oceanic crust forms along this ridge. The creation and destruction of oceanic crust means that continents move--it is a site of tectonic activity--helping form the Theory of Plate Tectonics
50
The Theory of Continental Drift suggested that continents move across the surface of Earth based on what inference?
The existence of a supercontinent Pangea
51
Which of the following observations were used to justify the existence of Pangea?
*The distribution of glacial features became contiguous when the continents were reassembled into Pangea
*The distribution of certain fossils became contiguous when the continents were reassembled into Pangea
*The continents fit together like a jigsaw puzzle
52
The supercontinent of Pangea included all of the modern continents except: _____
none (they were all included: greenland, india, antarctica
53
The existence of Pangea explained which of the following aspects of glacial geology?
*the direction of ice movement indicators on all five southern continents
*the existence of ancient glacial features in India, a place much too hot to support glaciers at its present latitude
*the distribution of ancient glacial deposits on all five southern continents
54
According to the Theory of Continental Drift, what moves across the surface of Earth?
continents
55
The average thickness of oceanic crust is
8 km
56
The graph below shows how the P-wave velocity of rock changes with depth:
What is a possible explanation for the change at B?
*there is a change from liquid above to solid below
*there is a change from one type of rock above to a different kind of rock below
57
Which of the following statements is true about the lithosphere?
*the lithosphere contains more than one composition of rock
*the lithosphere is a composite consisting of crust above rigid mantle
58
Which of the following statements about the asthenosphere is correct?
*the asthenosphere can be identified by a decrease in seismic wave velocity
*the asthenosphere is not 100% solid rock
59
Oceanic crust makes up what percentage of oceanic lithosphere?
7 (with margin: 0)
60
Which of the following statements are true about the difference between oceanic and continental lithosphere?
*oceanic lithosphere is on average more mafic than continental lithosphere
*oceanic lithosphere is denser than continental lithosphere
61
The Indian plate is converging with the Asian plate at what velocity?
about 1-10 cm/y
62
Use the tectonic plate map below to answer the following question:
Which of the following plates are made of both oceanic and continental lithosphere?
*erusian plate
*australian plate
*african plate
63
Which of these plates contain both continental and oceanic lithosphere?
*north american
*african
*indian
*south american
*eurasian
64
Use the tectonic plate map below to answer the following question:
Which plate doesn't contain any continental crust?
Nazca Plate
65
Which plate does contain any continental crust?
*australian plate
*antarctic plate
*african plate
66
According to the theory of Plate Tectonics, where is the lithosphere destroyed?
At subduction zones
67
Continental rifts eventually become what kind of plate tectonic boundary?
divergent
68
As you move away from a mid-ocean ridge, how does the thickness of oceanic crust change?
it remains constant
69
As you move away from a mid-ocean ridge, how does the water depth change?
It increases
70
Why does the oceanic lithosphere get thicker away from the mid-ocean ridge?
As rock cools, asthenosphere converts to lithosphere, thickening the lithosphere
71
A submarine exploring the seafloor encounters a large area with bare volcanic rock exposed on the surface. This area is most likely found:
on a mid-ocean ridge
72
What happens to the lithosphere at a continental rift?
it thins
73
As you move away from a mid-ocean ridge, how does the thickness of oceanic lithosphere change?
It increases
74
Which of the following statements is TRUE about the oceanic lithosphere around a mid-ocean ridge?
*the lithosphere contains more magma right at the ridge than away from the ridge
*the lithosphere right at the ridge is hotter than the lithosphere away from the ridge
*the lithosphere has volcanoes right at the ridge
75
Why is there very little sediment right at the mid-ocean ridge?
Too little time has passed to accumulate much sediment
76
You are trying to decided whether the edge of a continent is a passive margin or overlies a subduction zone. What features would indicate that this is a subduction zone setting?
*deep-sea trench in the adjacent ocean basin
*a chain of volcanoes parallel to the coast
*accretionary wedge sediments along the coast
77
Which of the following features is NOT found at a continent-continent collision?
volcanoes on the overriding plate
78
Melting in the mantle is always associated with what type of boundary?
Sudcution zone
79
Accretionary prisms contain what kind of material?
Sediments and sedimentary rocks shed off of the adjacent continent
80
The Wadati-Benioff Zone is
zone of intense deformation in the overlying plate of a subduction zone
81
Which of the convergent boundaries produce volcanoes?
O-C
O-O
82
Where does melting occur at a subduction zone boundary? (M3.5)
D
83
Accretionary prisms are most common along what kind of plate boundary?
continental-oceanic convergent boundaries
84
Where does the Wadati-Benioff zone occur?
in rocks of the downgoing tectonic plate at a subduction zone
85
What kind of stresses occur at transform boundaries?
shear
86
Which of the following statement is true about plate motions on a spherical earth?
*all plate motions occur as rotations about an Euler Pole
*transform faults are needed to accomodate different linear velocities within a plate
87
The diagram below shows two segments of mid-ocean ridge (in red). Is this a transform boundary here? Is so, where is it? (M3.6)
At B
88
The image below shows a section of seafloor with two segments of a mid-ocean ridge in red. Where is the oldest rock found? (M3.6)
B
89
The image belwo shows a section of seafloor with two segments of a mid-ocean ridge in red. Which of the following statements are TRUE about locations A and B? If you were to drive a submarine along the seafloor from B to A, what would happen? (M3.6)
The sediment thickness on the seafloor would increase as you got to A
90
What kind of stresses occur at transform boundaries?
Shear
91
The image below shows a section of seafloor with two segments of a mid-ocean ridge in red. Where is the youngest rock found? (M3.6)
C
92
The image below shows a section of seafloor with two segments of a mid-ocean ridge in red. Which of the following statements are TRUE about locations A and B?
*A and B are moving in the same direction
*Seafloor at A is older than seafloor at B
93
Consider three plates driven by three different processes:
Plate A is driven by ridge-push alone
Plate B is driven by slab-pull alone
Plate C is driven by both ridge-push and slab-pull
Which one do you expect to move the slowest?
Plate A
94
Very young oceanic lithosphere is less dense than the underlying asthenosphere. Under these conditions, which driving force for plate tectonics would not be possible?
Slab-pull
95
Which of the following statements is TRUE?
The ridge-push force is generated at the mid-ocean ridge
96
The slab-pull force requires that the subducting oceanic lithosphere is:
denser than the asthenosphere
97
Which answer correctly ranks the forces that drive plate tectonics, from the strongest to the weakest?
Slab-pull (strongest) > Ridge-push > Convection (weakest)
98
Which of the following statements is true about the ridge-push force?
The ridge-push force depends on an elevated asthenosphere
99
Which of the plate tectonic driving forces would vanish if there was no subduction on earth?
slab-pull
100
Which of the following best describes the driving force for plate tectonics provided by convection?
Convection is always a secondary force that arises from motions produced by either slab-pull or ridge-push
101
The map below shows the Hawaiian Islands, which were formed by hot spot volcanism. Volcano Mauna Keam on the Big Island of Hawaii, is active. Which of the following statements is true?
*the hot spot is located beneath the Big Island of Hawaii
*a chain of seamounts would likely be found northwest of the Hawaiian Islands
*Oahu is mored eroded than Maui
102
The best-know hot spot under continental lithosphere is:
Yellowstone Volcano
103
What causes hot spot plumes to rise?
They are less dense than surrounding rock
104
The evidence for the existence of hot spot plumes comes from:
seismic wave velocities in the Earth's deep mantle
105
Hot spots plumes are:
Rising columns of anomalously hot rock
106
The best-know hot spot under oceanic lithosphere is:
Hawaii
107
The driving force for rising hot spot plumes is:
Buoyancy
108
What is the formula for the polymorph of vaterite?
CaCO3
109
What is the formula for the polymorph of anatase?
TiO2
110
What kind of mineral is rhodochrosite?
Carbonate
111
What kind of mineral is sylvite?
salt
112
What kind of mineral is pyrite?
sulfide
113
What kind of mineral is barite?
sulfate
114
What kind of mineral is diopside?
silicate
115
What kind of mineral is stishovite?
silicate
116
What kind of mineral is hematite?
oxide
117
What is the polymerization of diopside?
single chain
118
What is the polymerization of talc?
sheet
119
What is the polymerization for albite?
framework
120
What is the polymerization for quartz?
framework
121
What is the polymerization for forsterite?
island
122
What is the polymerization for riebeckite?
double chain
123
What is the polymerization for jadeite?
single chain
124
What is the polymerization for lepidolite?
sheet
125
What is the polymerization for pyrope?
island
126
What is the polymerization for magnesiohornblende?
double chain
127
Does Rb substitute readily in K-spar?
True
128
Does Cs substitute readily in K-spar?
true
129
Does Sr substitute readily in Plagioclase?
true
130
Does Al substitute readily for Anhydrite?
False
131
Does Al substitute readily in Diopside?
False
132
Does Rb substitute readily in Diopside?
false
133
Does Ra substitute readily in Diopside?
false
134
Does Mg substitute readily in Calcite?
true
135
Does Al substitute readily in Calcite?
false
136
Does Mn substitute readily in Calcite?
True
137
What is the formula for quartz?
SiO2
138
What is the formula for calcite or aragonite?
CaCO3
139
What is the formula for gypsum?
CaSO4*2H2O
140
Which of the following is NOT a mineral at temperatures and pressures found on the surface of Earth?
Mercury Hg
141
Which of the following minerals is a polymorph of quartz (formula SiO2)?
Stishovite (formula SiO2)
142
Which of the following things is DIFFERENT across the boundary between two crystals of the same mineral?
The orientation of the crystal structure
143
Xenoliths are _______
rocks
144
Which of the following is NOT a rock?
Sand from the beach
145
Which of the following statements is TRUE about a bucket of quartz beach sand?
Many crystals are present
146
Which of the following statements is CORRECT?
Rocks contain minerals
147
Which of the following are essential properties of a mineral, according to the definition in the reading?
*A formula that specifies the occupancy of ions on each site
*A regular geometric arrangement of sites
*must be naturally occuring
148
Ions in octahedral coordination are bonded to how many surrounding anions?
6
149
Anions have a ________ charge.
negative
150
Cations are always _______ than their neutral atoms.
smaller
151
Which of the following ions can be in octahedral coordination with oxygen in minerals?
*Ca2+
*Al3+
*Mg2+
152
