Tectonic structures Flashcards
1
Q
define time
A
the age of the earth and therefore the rocks
2
Q
what is the time interval for catastrophism
A
very short time interval
3
Q
what is the time interval for uniformitarianism
A
medium length (longer than catastrophism but less than actualism)
4
Q
what is the time interval for actualism
A
very long time period
5
Q
what is actualism
A
a geological method that assumes current causes can explain past events that’s based on the idea that the same natural laws and processes that operate today have also operated in the past
6
Q
how does actualism differ from uniformitarianism
A
actualism acknowledges that Earth’s history includes periods of abrupt change, while uniformitarianism assumes that changes are gradual
7
Q
how is responsible for the THREE principles for sedimentary rocks
A
Nicholas Steno
8
Q
why is Nicholas Steno important
A
formed the three principles for sedimentary rocks
9
Q
what are the three principles for sedimentary rocks
A
superposition
original horizontality
lateral continuity
10
Q
describe the three principles for sedimentary rocks
A
superposition
- based on the layer of sediments were newer sediments are layered ABOVE older sediments
original horizontality
- sediments are deposited in horizontal layers and any deviations from that happened AFTER the beds were laid down
lateral continuity
- gaps between outcrops (like a river cutting a valley in half) don’t mean beds on either sides are different
11
Q
what do each letter represent (three principles of sedimentary rocks)
A
a) superposition
b) original horizontality
c) lateral continuity
12
Q
what is the fourth principle for sedimentary rocks added after Steno
A
cross cutting relationships
13
Q
what is the cross cutting relationship principle for sedimentary rocks
A
before anything can disrupt a sediment profile (like folding or faulting) the profile MUST be laid down before
14
Q
what causes increases in the structure of earth
A
mass accumulation and radioactivity
15
Q
what allows for stratification in earth’s structure
A
based on melting of various elements (forms layers)
16
Q
what is the core element rich in
A
iron
17
Q
what elements is the mantle rich in
A
iron, magnesium, silicon and aluminum
18
Q
what elements is the crust rich in
A
oxygen
oxygen seeking elements (silicon, aluminum, calcium, sodium and potassium)
19
Q
describe the characteristics of crust
A
lightest (lightest in elements and mass) , coolest and thinness layer
20
Q
what is the thickness range for lithosphere
A
5 to 250 km thick
21
Q
where is the lithosphere thinnest
A
the ocean crust
22
Q
where is the lithosphere the thickest
A
under mountains
23
Q
what layer of earth is known as brittle shell
A
lithosphere
24
Q
what are the layers of earth
A
inner core
outer core
mesosphere
asthenosphere
lithosphere
25
what is the thickness of the asthenosphere
660 km
26
what layer of earth is mechanically weak
asthenosphere
27
what determines how each layer of earth behaves
1. composition
2. heat
3. pressure
28
what are the two layers of the mantle
lower: mesosphere
upper: asthenosphere
29
is the mesosphere weaker or stronger than the asthenosphere
stronger
30
what layer(s) of earth hold convection currents
the mesosphere AND the asthenosphere
31
what is the thickness of the outer core
2270 km
32
what state is the outer core
liquid
33
what is the state of inner core
solid
34
what is the thickness of the inner core
1216 km
35
1
crust
36
2
mantle
37
3
core
38
4
lithosphere
39
5
asthenosphere
40
6
mesosphere
41
7
outer core
42
8
inner core
43
what is the moving surface of the planet
plate tectonics
44
what was the original paradigm of the world
continents and oceans were static entities and mountains were created by an unknown forced in earth's interior
45
how were mountains thought to have been created in original paradigm
for every mountain range that grew some part of the planet sank below sea level
46
why is Wegner important
came up with the idea that continents moved (continental drift)
47
why was Wegner ridiculed
because he could not provide a mechanism for his theory of continental drift
48
where was the method of continental drift found by
mapping the sea floor showed massive mountain ranges and volcanic activity
49
over time what was the mechanism that developed for continental drift
magnetic anomalies at ocean plate boundaries
50
what was geologic evidence for continental drift
rock units on different continents with SIMILAR structural styles line up into continuous chains if Pangea is reconstructed
51
what is palaeontologic evidence for continental drift
based on how fossils of different species were found on similar continents suggesting migration patterns over time before the continents separated
52
what is climatic evidence for continental drift
today with continents separated glaciers seem to have moved out from ocean HOWEVER we known glaciers form middle of continent before spreading in all directions
53
what is the mechanism for plate tectonic movement
convection currents
54
what crust subdues under another
the HEAVIER one ALWAYS subducts under another plate
55
what are three types of plate boundaries
1. divergent
2. convergent
3. transform
56
describe the divergent boundary
When plate material on either side of the boundary spreads apart
57
describe the convergent boundary
when two plates move towards each other, and one plate often subducts beneath the other
58
describe the transform boundary
when two plates slide past each other in opposite directions
59
what type of landform forms with a divergent boundary
rift valley
60
what type of landform forms with a transform boundary
fences and rivers don't line up anymore
61
what type of landform forms with a convergent boundary
mountains
62
what is deformation
general term that refers to all changes in original form/size of a rock body
63
where does crust deformation occur
along or near plate margins
64
contrast stress vs strain
stress
- the force applied to a given area
strain
- the visible response to stress (changes in shape or size of rock body by stress)
65
what is force
puts stationary objects in motion or changes motion of moving bodies
66
is strain the same as stress
NO
67
four types of stress
1. differential stress
2. compressional stress
3. tensional stress
4. shear stress
68
differential stress
stress applied UNEQUALLY from DIFFERENT directions
69
compressional stress
stress that SHORTENS a rock body
70
tensional stress
stress that elongates a rock body
71
shear stress
stress is applied in OPPOSITE directions
72
what type of plate boundary has compressional stress
convergent
73
what type of plate boundary has tensional stress
divergent
74
what type of plate boundary has shear stress
transform
75
1
tensional stress
76
2
compressional stress
77
3
shear stress
78
what causes deformation of earth's crust
tectonic forces and associated stress
79
how can rocks deform
when rocks are subjected to stresses greater than their own strength begin to deform
80
what are methods of deforming rocks
1. faulting
2. folding
3. fracturing
81
how can rocks bend
when rocks have been subjected to the RIGHT amount of heat (not too much or else fractures)
82
what are two types of deformation
brittle and ductile deformation
83
describe brittle and ductile deformation
brittle
- fractures of rock that happens at low temps and pressures near the surface
ductile
- plastic breakage when temps and pressures are high
84
type of deformation
brittle (fracture)
85
type of deformation
fold (ductile)
86
what two factors determine a rock's deformation
rock type and time
87
does stress over short or long time intervals cause large changes in rocks
small stress over LONG time
88
what is an outcrop
places were bedrock is exposed at the surface
89
how does a geologist study a region
identify and describe the dominant rock structures
90
what is a give away for a transform plate
z-zag
91
what must be done to determine how the rock has moved/deformed
determining its orientation
92
how can the orientation of a rock be found
strike and dip method
93
describe the strike and dip method for orientation of rock
strike
- the compass direction of the line produced by the intersection of inclined rock layer/fault with horizontal plane
dip
- angle of inclination of the surface of a rock unit measured from horizontal plane ALWAYS measured 90 degrees to strike
94
folds
rocks bent into series of wave-like undulations during crustal deformation
95
what most commonly forms folds
result from compressional stresses which shorten and thicken the crust
96
what are the 4 parts of a fold
1. limb
2. axis
3. plunge
4. axial plane
97
what are the limbs of a fold
refers to the two sides of a fold
98
what is the axis of a fold
line drawn down crest of the fold
99
what is a plunge of a fold
a fold axis inclined at an ANGLE
100
what is the axial plane of a fold
imaginary surface that divides a fold as symmetrically as possible
101
types of folds
1. anticline
2. syncline
3. monoclines
102
anticline fold
a geological formation that occurs when rock layers fold into an arch shape, with the oldest rock in the center
103
syncline fold
a fold in the earth's crust where rock layers curve downward, with younger layers closer to the center of the fold
104
monocline fold
large step like folds in otherwise horizontal sedimentary strata
105
what are characteristics of folds
1. symmetrical
2. asymmetrical
3. recumbent (fold lying on sides)
4. plunging
5. overturned
106
monocline
107
anticline
108
syncline
109
are domes and basins folds or faults
folds
110
domes
up-warped displacement of rock
111
where is old and young rock found in domes
old - center
young - flanks
112
basins
down-warped displacement of rocks
113
where is young and old rock found in basins
young - middle
old - flanks
114
where do limbs dip in basins
TOWARDS the middle
115
where do limbs dip in domes
AWAY from middle
116
are domes more like anticlines or synclines
anticlines
117
are basins more like anticlines or synclines
synclines
118
dome or basin
dome
119
what are joints
fractures that result from brittle deformation with NO MOVEMENT
120
what is one of the most common rock structures
joints
121
what type of groups do joints occur in
parallel groups
122
what are causes of joints
1. columnar joints (igneous)
2. brittle fractures due to crystal deformation
123
what are columnar joints
a network of fractures that create a pattern of columns in igneous rocks, such as lava flows
124
do rocks with less joints show more weathering
NO - more joints cause more weathering
125
where is chemical weathering concentrated
along joints
126
are highly jointed rocks more or less stable than less jointed rocks
LESS = more weathering will act on it
127
faults
fractures in rocks along which displacement takes place (there is some kind of movement of the rock)
128
what causes earthquakes
SUDDEN movements on faults
129
what are results of faults
1. fault gouges
2. fault polish
3. slickensides
130
how are faults classified
by relative movement
131
what types of movements can faults undergo
1. horizontal
2. vertical
3. oblique
132
types of faults
1. dip slip (reverse and normal)
2. strike-slip (transform)
133
type of fault (1)
right lateral strike slip
134
type of fault (1)
normal
135
type of fault (2)
left lateral strike slip
136
type of fault (2)
reverse
137
what movement is in dip slip faults
movement is PARALLEL to the dip of the fault surface
138
what are fault scarps
long low cliffs produced by up and down displacement
139
describe the two walls in a dip slip fault
hanging wall
- rock ABOVE the fault surface
footwall
- rock BELOW the fault surface
140
three major types of dip slip faults
1. normal
2. reverse
3. thrust
141
how do reverse and thrust dip slip faults compare
both are reverse faults (with hanging wall pushing up against gravity) HOWEVER a thrust fault has a GENTLER slope compared to reverse faults
142
normal fault
hanging wall MOVES DOWN relative to the footwall
143
describe what happens to the crust in normal faults
thinning of the crust
144
type of plate boundary associated with normal faults
divergent boundary (extension)
145
describe two regions in a normal fault
graben
- center block bounded by NORMAL faults that DROPS as the plates separate
Horst
- raised blocks between grabens bounded by normal faults
146
type of fault
normal fault
147
movement of hanging wall in reverse faults
moves UP relative to the footwall block
148
type of plate boundary where reverse faults are found
convergent boundary
149
describe crust in reverse faults
shortening of crust
150
what angle indicates a reverse fault? thrust fault?
reverse fault = angle GREATER than 45 degrees
thrust fault = LESS than 45 degrees
151
normal fault
152
reverse fault
153
thrust fault
154
dominant displacement in stroke-slip faults
horizontal and parallel to the strike of the fault
155
types of strike-slip faults
right and left lateral faults
156
what part of the earth does a strike slip fault cut through
the lithosphere
157
what links spreading ocean ridges
strike-slip fault
158
examples of strike-slip faults
san Andreas Fault
159
what type of boundary shows strike-slip fault
transform boundary
160
two processes that classify tectonic landforms
constructional landforms (aggregation)
destructional landforms (deaggregation)
161
examples of depositional landforms
1. alluvial fans
2. deltas
162
type of processes contributed to aggregation landforms
1. depositional processes
2. endogenic processes
163
what landforms are depositional processes responsible for
1. alluvial fans
2. deltas
164
what are endogenic processes responsible for
orogenies (mountains) and regional uplift
165
what are destruction processes involving
removal of material (weathering and erosion)
166
are destructional landforms based from exogenic or endogenic processes
exogenic
167
are constructional landforms based from exogenic or endogenic processes
endogenic
168
where do endogenic processes work
WITHIN the earth
169
what process produced INITIAL landforms
endogenic processes
170
what powers endogenic processes
earth's internal energy (convection currents)
171
what process brings fresh rock to surface
endogenic processes
172
where do exogenic processes work
at earth's surface
173
does endogenic or exogenic processes wear down landforms
exogenic
174
what process is responsible for SEQUENTIAL landforms
exogenic processes
175
what are fold belts
compression from tectonic activity producing folds in the rock strata (anticlines and synclines)
176
what force forms fold belts
compression
176
what erodes to form ridge and valley landscapes
fold belts
177
how does fault slippage vary
from 1 cm to 15 cm
178
how are strike-slip faults (transcurrent) produced
tectonic plates move past each other HORIZONTALLY
179
how are reverse/thrust faults produced
compression in the crust (convergent plates)
180
how can landscapes have high fault scarps
through repeated faulting
181
what does rock structure control for tectonic landforms
1. locations of uplands
2. locations of lowlands
3. placement of streams
4. shape and height of divides
182
structures in arid regions due to tectonic movement
1. plateaus
2. mesas
3. buttes
183
1
mesa
184
2
butte
185
3
plateau
186
landforms in costal plains
1. consequent streams
2. subsequent streams
3. cuestas
187
metamorphic belts
rocks undergo compressional strees under surface with just enough heat to form a metamorphic belt
188
what can metamorphic belts form
ridges (hard rock) and valleys (soft rock)
189
what type of metamorphic rock forms valleys
marble
190
what type of metamorphic rock forms ridges and hills
1. gneiss
2. schist
3. slate
4. quartize
191
batholiths
huge body of intrusive IGNEOUS rock that forms hilly or mountainous uplands
192
Monadnock
a mountain that arises out of a surrounding plain
193
why do Monadnocks develop
because it consist of more resistant rock than the surrounding region.
