Exam 2 Study Guide Flashcards
1
Q
What is the difference between magma and lava?
A
Magma: the molten/partially molten material found beneath the surface of the Earth
Lava: magma once it reaches the Earth’s surface.
2
Q
Where does magma form in terms of plate tectonics?
A
Divergent boundaries at the mid-ocean ridge and continental rifts and Convergent boundaries in subduction zones
3
Q
What are the 3 ways to generate magma?
A
- Decompression melting
- Addition of volatiles
- Addition of heat
4
Q
What is decompression melting?
A
Melting occurs when the body of rock is held at the same temperature, but the pressure is reduced.
5
Q
Where do we see decompression melting in terms of plate tectonics?
A
At a mantle plume, mid-ocean ridge, or continental rift
6
Q
What is the addition of volatiles?
A
Water lowers the melting temperature of the mantle to generate partial melts.
7
Q
Where do we see the addition of volatiles in terms of plate boundaries?
A
Subduction zones
8
Q
What is the addition of heat?
A
When some other mechanism generates magma to intrude into the cold crust, it brings the heat with it.
9
Q
Where do we see the addition of heat in terms of plate boundaries?
A
Hot spots and continental rifts
10
Q
What are the 3 ways magma evolves?
A
- Fractionation
- Assimilation
- Magma mixing
11
Q
Compare intrusive and extrusive igneous rocks.
A
Intrusive: formed from magma that cools slowly and the result is that these rocks are coarse-grained,
Extrusive: cool quickly and as a result, these rocks are fine-grained or lack crystal growth.
12
Q
What are the 5 intrusive environments?
A
- Dike
- Sill
- Plutons
- Laccolith
- Batholiths
13
Q
What are the 3 different compositions of magmas (igneous rocks)?
A
- Felsic
- Intermediate
- Mafic
14
Q
What are the 6 textures of igneous rocks?
A
- aphanitic (fine-grained)
- Phaneritic (coarse-grained)
- Porphyritic
- Glassy
- Pyroclastic
- Pegmatitic
15
Q
What is aphanitic texture?
A
- fine-grained “invisible”
- Microscopic crystals
- Rapid cooling of lava/magma
- May contain vesicles (holes from gas bubbles)
16
Q
What is phaneritic texture?
A
- (coarse-grained) texture
- crystals large enough to see with the naked eye
- slow cooling of magma
- intrusive origin
17
Q
What is porphyritic texture?
A
- 2 different sizes of crystals
- Minerals form at different temperatures and rates
- Can indicate two stages of cooling
18
Q
What is glassy texture?
A
- Very rapid cooling of molten rock
- Extrusive origin
19
Q
What is pyroclastic texture?
A
- extrusive origin
- Various fragments ejected during a violent volcanic eruption
20
Q
What is pegmatitic texture?
A
- exceptionally coarse-grained texture
- found in intrusive igneous rocks
- forms in the late stages of crystallization of granitic magmas
21
Q
Igneous rocks form when:
A
a melt solidifies at or below the Earth’s surface
22
Q
The molten rock beneath the Earth’s surface is called ____.
A
magma
23
Q
The greatest amount of magma is created at _____________.
A
divergent plate boundaries
24
Q
How is magma generated at subduction zones?
A
Addition of volatiles
25
Which type of magma contains the lowest amount of silica?
Mafic
26
_____ is a mafic extrusive igneous rock.
basalt
27
A _______ is a concordant igneous rock body which runs parallel to the pre-existing bedrock.
Sill
28
Magma rises toward the Earth's surface because:
it is less dense than the surrounding rocks
29
Why are intrusive igneous rocks from a batholith generally coarser-grained than those from volcanic vents?
They are cooled more slowly and thus have more time to grow.
30
A _____ texture indicates two stages of cooling
porphyritic
31
Compare explosive and effusive eruptions.
Explosive: Felsic and intermediate lavas thtat can generate deadly pyroclastic flows
Effusive: Mafic lavas with gentle flowing lava due to low viscosity
32
Compare Fissure and vent eruptions
Fissure: lava emerges from a fracture or cracks in the ground rather than from a central vent
- Common:
+ Where the crust is undergoing extension; continental rifts and mid-ocean ridges
+ Where magma has low viscosity (relatively fluid)
- They are the dominant style of eruption
Vent: magma is extruded at a central vent
33
How are mafic lava eruptions characterized?
Effusive/less violent
34
What are the effects of mafic lava eruptions? (lavas and volcanoes)
- Pillow lavas
- Ropy lava (pahoehoe)
- Blocky lava ('a,'a)
- Shield volcanoes
- Cinder cones
35
How are felsic and intermediate lavas characterized?
Explosive/more violent
36
What are the effects of intermediate and felsic lavas?
- Tephra; classified by size
- Stratovolcanoes
- Lava domes
- Continental calderas
37
What are the major volcanic hazards? (2)
- pyroclastic flow
- lahars
38
A lava flow whose surface is broken into rough angular fragments is:
a'a
39
Tephra comes in three sizes; _____ is the smallest
ash
40
_______ are avalanches of hot ash, rock, volcanic glass fragments, and gas that race down the sides of the volcano during an eruption.
pyroclastic flows
41
The most abundant volcanic gas is _____.
water vapor
42
A _____ is a Volcanic mudflow/debris flow.
lahar
43
What is the most common risk to humans from lava flows?
Property damage.
44
Which of the following is NOT a common cause of pyroclastic flows?
a. boiling over from an eruptive vent
b. collapse of eruption column
c. collapse of lava domes or flows
d. megathrust earthquakes
d. megathrust earthquakes
45
T/F: Lahars are only triggered by volcanic eruptions.
False
46
____ eruptions are typically associated with shield volcanoes.
Effusive
47
A ____ is a solid rock fragment greater than 64mm in diameter that was ejected from a volcano during an explosive eruption.
block/bomb
48
What are the classifications of tephra
1. Ash <2 mm
2. Lapilli 2-64 mm
3. Bomb >64 mm
49
Compare physical (mechanical) and chemical weathering.
Physical:
- mechanical breakdown of rock into smaller fragments
- provides a fresh surface for a chemical attack
- creates sedimentary clasts (sediments) that can become clastic sedimentary rock
Chemical:
- chemical change of the minerals within the rock to forms that are stable in the surface environment
- weakens the rock so it is more susceptible to mechanical weathering
- creates ions in solution that can eventually become sedimentary rock.
50
What are the 7 types of mechanical weathering?
1. Impacts/ Abrasion
2. Freeze-Thaw Action (Frost/Ice Wedging)
3. Temperature Changes
4. Salt Crystal Growth
5. Pressure Relief
6. Wetting and Drying
7. Biological Activity
51
What causes chemical weathering?
- Lower temperature
- Lower pressure
- Higher free water
- Higher free oxygen
52
What minerals are more susceptible to chemical weathering?
- Halite
- Calcite
53
What are the 3 types of chemical weathering?
1. Dissolution (Solution)
2. Hydrolysis
3. Oxidation
54
What controls weathering?
- Rock Type and Structure
- Slope
- Climate
- Vegetation
- Animals
- Soil
- Length of exposure
55
Give an example of impacts/abrasion.
A rock falling from a cliff and breaking itself and other rocks it hits en route.
Sand grains blown by the wind or carried by water abrade both themselves and anything they strike.
Boulders carried by glacial ice scour, abrade, and fragment themselves and any rock they come in contact with
56
Give an example of frost/ice wedging
Water in a joint is freezing and forcing the joint to open.
57
Give an example of temperature changes.
Enchanted Rock TX
58
Give an example of salt crystal growth.
Honeycomb weathering of sandstone on Gabriola Island
59
Give an example of pressure relief.
A previously buried mass of rock is exposed by uplift
60
Give an example of biological activity.
A tiny root hair seeking out a small crack in a rock, then it grows and expands cracking the rock.
61
How does rock type and structure affect weathering?
Different rocks are composed of various minerals, each with a distinct susceptibility to weathering.
62
How does slope affect weathering?
Steep slopes: weathering products are quickly washed away by rain
Gentle slopes:
- weathering products accumulate
- water may stay in contact with rock for longer periods
- higher weathering rates
63
How does climate affect weathering?
Higher amounts of water and heat cause chemical reactions to run faster.
64
How does vegetation affect weathering?
Plants:
- produce organic acids that help break down rocks
- help the soil retain moisture
- roots widen cracks
65
How do animals affect weathering
Burrowing organisms bring material to the surface where it can be exposed to agents of weathering.
66
How does soil affect weathering?
- retains rainwater
- host to a variety of vegetation, bacteria, and organisms that produce an acidic environment
67
How does the length of exposure affect weathering?
The longer a rock is exposed to the agents of weathering, the greater the degree of alteration, dissolution, and physical breakup.
68
What property of water is most directly responsible for frost wedging?
The expansion of water as it changes from a liquid to a solid.
69
Sheet jointing or exfoliation of plutonic rocks is usually produced by _________.
pressure release
70
How does mechanical weathering aid chemical weathering?
Mechanical weathering increases the surface area for a chemical attack.
71
Which of the following is not a form of physical weathering?
A. dissolution (solution)
B. impacts/abrasion
C. frost wedging
d. salt crystal growth
A, dissolution (solution)
72
When an exposed rock bakes in the Texas sun it ____.
expands
73
Salt crystal growth (salt wedging) is common in ___ climates and coastal areas.
arid
74
T/F: When a rock is mechanically weathered, it changes composition.
F
75
Rocks can be "sand-blasted". This is a type of mechanical weathering termed _______.
impacts/abrasion
76
Alternate wetting and drying of soft/poorly-cemented rock (shales) cause fairly rapid breakdown of the rock. Most disintegration occurs during the ____ cycle.
drying
77
What type of mechanical weathering is exemplified by a tree growing in the middle of a rock?
Biological activity.
78
What affects the rate of chemical weathering of a mineral?
The composition of the mineral, type of weathering, grain size, and climate among other factors.
79
___ and ____ climates promote the fastest chemical weathering.
Hot;wet
80
The mineral that is the most resistant to weathering is _____.
Quartz
81
Given your understanding of weathering processes, what is responsible for the red color of the rocks and soils around the Red River in North Texas?
Oxidation of iron-bearing minerals.
82
____ is one of the most water-soluble minerals.
Halite
83
The mineral hematite forms from which chemical weathering process?
a. salt wedging
b. solution/dissolution
c. hydrolysis
d. oxidation
d. oxidation
84
The __ a rock is exposed to the agents of weathering, the greater the degree of alteration, dissolution, and physical breakup.
longer
85
What causes most rainwater to be slightly acidic?
Carbon Dioxide in the air reacts with water to form carbonic acid.
86
Compare clastic, biochemical, and chemical sedimentary rocks.
Clastic:
- form from the breakdown of preexisting rock into sediment (clasts)
- classified by grain size
Biochemical:
- precipitated first in the tissue of organisms, then deposited when the organism dies
Chemical:
- form from precipitated material that was once in solution (ions)
- usually have a crystalline structure
- precipitation of material occurs by inorganic processes like evaporation.
87
How does the Udden-Wentworth grain size scale categorize grains as gravel, sand, slit, and clay?
Clay: <1/256th mm
Slit: 1/256th mm - 1/16th mm
Sand: 1/16th mm - 2 mm
Gravel: 2 mm+
88
What are the 5 steps of sedimentary rock formation?
1. Weathering
2. Erosion
3. Transportation
4. Deposition
5. Burial and Lithification
89
How are sorting and shapes used to classify clastic sedimentary rocks?
If grains in a rock are of similar size, it is well sorted
If grains in a rock are different sizes the rock is poorly sorted
Rounded sediments have been transported great distances
angular sediments are only transported a short distance.
90
Compare arnite and wacke.
arnite: clean sandstone with less than 15% slit and clay
wacke: sandstone with more than 15% slit and/or clay
91
What are the 6 types of clastic sedimentary rocks?
1. Conglomerate
2. Breccia
3. Mudrock
4. Shale
5. Sandstone
6. Slitstone
92
What are the 5 types of biochemical sedimentary rocks?
1. Fossiliferous limestone
2. Coquina
3. Chalk
4. Coal
5. Biochemical chert
93
What are the 6 types of chemical sedimentary rocks?
1. Travertine
2. Tufa
3. Oolitic limestone
4. Dolostone
5. Evaporite
6. Chemical Chert
94
What are the depositional environments of sedimentary rocks?
1. Continental
2. Transitional
4. Marine
95
What are the sedimentary structures?
1. Layers of sedimentary rocks (strata)
2. Graded beds (deposited from waning current)
3. Cross-bedding (sediments come to rest at an angle)
4. Ripple marks (to-and-fro motion of waves)
5. Mud cracks
96
The most abundant sedimentary rocks are ______.
Mudrocks/shales
97
A clay-sized sedimentary particle measures:
less than 1/256 mm
98
If an aggregate of sediment consists of particles that are all about the same size, it is said to be _____.
well sorted
99
How does breccia differ from conglomerate?
Particles in breccia are more angular.
100
______ forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores.
Chalk
101
Which is best classified as a biochemical (organic) sedimentary rock?
a. Travertine that forms when calcium carbonate precipitates from water flowing through a cave
b. Halite that forms when seawater evaporates
c. Oolitic limestone that forms when calcite precipitates in the layers around a central fragment
d. Fossiliferous limestone that is made of calcite extracted from seawater by marine organisms
d. Fossiliferous limestone that is made of calcite extracted from seawater by marine organisms
102
____ is a sedimentary rock that forms from the accumulation of plant remains.
coal
103
Which of the following is not a continental environment?
a. stream
b. desert sand dune
c. delta
d. glacier
c. delta
104
Deep marine deposits (sediments) are typically _____-______.
fine-grained
105
A/An ______ is a small (1 mm) sphere of calcite formed in areas of tropical shallow marine water with strong currents.
ooid
106
Define metamorphism.
The transformation of rocks
107
What is metamorphic grade?
The degree that which the parent rock changes during metamorphism.
108
What are the 3 metamorphic agents?
1. Temperature
2. Pressure
3. Hot fluids
109
How does temperature and pressure affect metamorphic grade?
Low temperature and pressure = low metamorphic grade
High temperature and pressure = high metamorphic grade
110
Compare foliated and non-foliated metamorphic textures.
Foliated: differential stress causes the platy mineral crystals to slide parallel to and past one another.
Non-foliated: crystalline structure and coarse-grained
111
What are the 4 types of foliated metamorphic rocks?
1. Gneiss - dark and light banding
2. Phyllite - wavy and/or wrinkled; satiny/metallic luster
3. Schist - platy minerals are discernible with the naked eye
4. Slate - rock splits into thin sheets
112
What are the 3 types of non-foliated metamorphic rocks?
1. Quartzite - sandy texture
2. Marble - crystalline texture
3. Hornfels - fine-grained
113
What is a protolith?
The original parent rock.
114
What are the protoliths of marble?
Limestone
Dolostone
115
What is the protolith of quartzite?
Quartz sandstone
116
What is the protolith of slate?
Shale
117
What is the protolith of phyllite?
Shale
118
What is the protolith of schist?
Shale
119
What is the protolith of gneiss?
Shale
120
What are the 5 metamorphic environments?
1. Burial metamorphism
2. Contact/thermal metamorphism
3. Hydrothermal metamorphism
4. Regional metamorphism
5. Subduction zone metamorphism
121
What is mylonite?
Rocks formed in regions where minerals form a foliated or lineated appearance.
122
What is impact metamorphism?
What occurs when asteroids/comets strike Earth's surface which produces fused fragmented rock plus glass-rich ejecta that resemble volcanic bombs
123
A metamorphosed equivalent of a limestone would be a ___.
marble
124
Gneiss ___________.
shows dark and light bands of minerals.
125
A place where rocks are probably being subjected to contact metamorphism.
A mile under St. Helens
126
Which of the following metamorphic rocks displays a foliated texture?
a. marble
b. quartzite
c. schist
d. hornfels
c. schist
127
Which of the following is not a useful metamorphic mineral?
a. quartz used to make glass
b. diamond used to make saw blades, drill bits, and gemstones
c. graphite used in lubrication and to make pencil leads
d. garnets used in abrasives and to make gemstones.
a. quartz used to make glass
128
The original (parent) rock that has undergone metamorphism is called the _____.
protolith
129
Which foliated texture would be most likely to develop in beds of shale with low-grade metamorphism?
a. schistosity
b. fissility
c. gneissic branding
d. shale
d. shale
130
_____ ______ produces the greatest quantity of metamorphic rock.
regional metamorphism
