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EV11001 > Geology > Flashcards

Geology Flashcards

1
Q

How old is earth

A

4.5 billion years old

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2
Q

Earths radius

A

6371km

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3
Q

What two elements are most abundant in the earths crust

A

Oxygen 45.2% Silicon 27.2%

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4
Q

What causes changes in the geological time scale

A

mass extinctions and change in climate

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5
Q

What is stratigraphy

A

study of rock layers

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6
Q

What are stenos three laws

A

law of original horizontally
law of superposition(oldest at bottom)
law of original continuity(erosion)

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7
Q

what does brittle deformation cause

A

(snaps) faulting

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8
Q

what does ductile deformation cause

A

(stretch) folds

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9
Q

What are the three types of faults

A

normal
reverse/thrust
strike slip

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10
Q

What are the two components of a fold

A

the hinge(peak) and the limb(side)

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11
Q

What are the four types of a fold

A

upright(equal forces)
inclines(one stronger)
overturned(limbs over each other)
recumbment

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12
Q

What is the antcline and syncline of a fold

A

anticline is oldest rock in middle
syncline is youngest at bottom

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13
Q

what are the 3 fundamental rock groups

A

igneous
sedimentary
metamorphic

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14
Q

what is volcanism

A

the transfer of heat and matter betweeen earths interior and its surface

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15
Q

what are volcanoes

A

openings or vents where lava, tephra and gasses escape onto earths surface

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16
Q

what are igneous rocks

A

rocks that are a product of volcanoes and volcanism

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17
Q

how are igneous rocks formedd

A

minerals crystallising from a melt known as magma ie cooling of magma and/ or lava (magma on earths surface)

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18
Q

what are the two types of igneous rocks

A

intrusive/plutonic- magma cools and solidifies deep underground
extrusive/volcanic- magma cools and solidifies at the surface as lava

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19
Q

how can crystal size be used to classify igneous rocks

A

intrusive- cooled slowly deep so are more course grained or phanertic(>1mm)
extrusive- cooled quickly at surface so no tike to grow, fine grained or aphanitic (<1mm)

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20
Q

How can chemical composition be used to identify igneous rocks

A

the amount of chemical compounds in particular SiO2, can affect colour

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21
Q

what is a dike

A

magma extrudes vertically through existing fractures in rocks

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22
Q

what is a sill

A

horizontal intrusions occur when magma exploits weaknesses in horizontal layers

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23
Q

what are the characteristics of an effusive eruption

A

basic, low viscosity, thin and runny lava, hottest, produces wide land forms with low slopes, found at constructive margins and hot spots, frequent but gentle erosion’s

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24
Q

what are the characteristics of explosive eruptions

A

acidic, high viscosity, thick and sticky lava, produces steep sides cones, found and destructive margins to produce subduction zones, infrequent violent eruptions

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25
Q

what types of volcano does low magma viscosity produce

A

shield volcano- wide gentle cones

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26
Q

how are sedimentary rocks formed

A

the accumulation of material derived from the physical disintegration and chemical decomposition of older rocks

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27
Q

what are thr four processes involved in sedimentary rocks production

A

weathering- breaking up of pre-existing rocks
erosion- transportation of the particles either as solid particles or in a solution
deposition- and accumulation of the particles(or chemical precipitation)
lithification- cementation of a sediment so that it becomes a rock

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28
Q

how to classify sedimentary rocks

A

clastic- subdivides by grain size
chemical- subdivided by type of chemical precipitation
organic- subdivided by origin of organic material

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29
Q

what is layering (sedimentary)

A

a general term for any
type of layering in a sedimentary
rock

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30
Q

what is bedding (sedimentary)

A

large distinct layers of
sedimentary rock that form over
time due to changes in
depositional conditions (>1cm)

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31
Q

what is lamination (sedimentary)

A

very thin layers
within a bed (mm thick), formed by
minor variations in deposition

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32
Q

what are asymmetric ripple marks (sedimwntary)

A

ripples indicate flow direction, with the steep
slope on the down-current direction.what

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33
Q

what are symmetric ripple marks (sedimentary)

A

ripples form as a result of constant wave
energy oscillating back and forth

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34
Q

what is cross bedding (sedimentary)

A

beds inclined relative to one another in the direction if wind or water, boundaries between represent an erosion surface, common in beach deposits

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35
Q

what is graded bedding (sedimantary)

A

As current velocity decreases, first the larger or more dense particles
are deposited followed by smaller particles.
Multiple graded-bed sequences called turbidites

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36
Q

what are the two types of metomorphism

A

contact and regional

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37
Q

what is contact metamorphism

A

when rocks encounter a heat sources eg magma without significant pressure

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38
Q

how does the extent of metamorphism vary

A

with distance from igneous rock

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39
Q

what is regional metamorphism

A

formed during mountain-building (orogeny), at
collision of lithospheric plates (destructive plate margins), combined effect of increased temperature and pressure

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40
Q

what is diagenesis (metamorphism)

A

all physical, chemical and biological
changes that occur in sediments after they are
deposited but before they become metamorphic rocks

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41
Q

chemical characteristics of continental crust

A

10-70 km thick
granitic so mostly made of oxygen and silicon

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42
Q

chemical characteristics of oceanic crust

A

2-10 km thick
basaltic so more magnesium, less silicon than continental crust

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43
Q

chemical characteristics of mantle

A

3488 km thick
made of peridotite
solid but deforms so can convect

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44
Q

chemical characteristics of the core

A

2882 km radius
made of iron and small amounts of nickel

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45
Q

physical properties of the litosphere

A

100 km thick

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46
Q

physical properties of the asthenosphere

A

250-350 km thick
viscous, soft and flow easily

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47
Q

physical properties of the mesophere

A

2500 km thick
capable of flowing

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48
Q

physical properties of the inner core

A

1230 km radius
iron and nickel, solid

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48
Q

physical properties of the outer coer

A

2250 km thick
iron and nickel, liquid

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49
Q

ways to know the chemical and physical composition of earth

A

seismology
drill holes
exposures
mineralogy

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50
Q

What are the two types of seismic waves

A

body (p and s) waves
travel through earths inner layers
surface (love and raleigh) waves
can only move along earths surface

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51
Q

P Wave

A

primary, fastest wave
moves through solid and fluids
particles move in the same direction as wave propagation

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52
Q

S Wave

A

secondary wave, slower than P
only moves through solid rock
particles move up and down or side to side ie perpandicular to wave propagtion

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53
Q

Surface waves

A

only travel through earths crust, lower frequency
arrive after body waves

54
Q

Love waves

A

fastest surface waves
move side to side

55
Q

Rayleigh waves

A

Roll along ground, moving up and down and side to side

56
Q

what is a seismograph

A

Detects and records vibrations
produced by seismic waves
generated from earthquakes,
volcanic eruptions or human
activity
Seismogram
shows amplitude
and frequency of
seismic waves

57
Q

what are the two ways to measure seismic activity

A

richter scale, max amplitude of seismic wave
modified mercalli, amount of intensity, shaking and damage

58
Q

how do seismic waves provide evidence for the earths structure and composition

A

waves travel
quicker though denser materials, so faster with depth
slower through hot areas
slower through a liquid than a solid
P waves slower through molten areas

59
Q

what are seismic discontinuities

A

Sudden change in
seismic velocities across a geological
boundary
Results in reflections, refraction (bending),
and the production of new wave phases (e.g.,
an S wave produced from a P wave)

60
Q

what are the 5 major seismic discontinuities in the earths interior

A

moho
LVZ
670 km
gutenburg
lehmn

61
Q

what is the moho(rovicic) disconitnuinty

A

seismic waves from
shallow-focus earthquakes were
recorded twice on seismograms: 2 sets
of P-waves and 2 sets of S-waves [first
set is direct path, second is
refracted/reflected when hitting
boundary]
One set must have travelled more slowly
(i.e. through the upper part of the crust)
and one through a faster medium

62
Q

what is the LVZ (low velocity zone)

A

Represents zone of weakness in the
upper mantle called the
asthenosphere

63
Q

what is the 670 km seismic discontinuity

A

Results from a phase change in mantle minerals
is a major boundary separating less dense upper
mantle from a more dense lower mantl

64
Q

what is the gutenberg discontinuity

A

found at Core-Mantle Boundary
molten core beginning at ~2900
km depth. S (Shear) waves
could not penetrate this molten
layer and P waves would be
severely slowed and refracted –
thus the outer core must be
liquid.
Evidence for internal Earth structure and composition

65
Q

what is the lehman discontinuity

A

found in the inner core
a sudden increase
in P wave velocities at a depth of
5150 km.
This velocity increase is
consistent with a change from a
molten outer core to a solid inner
core

66
Q

what was the evidence that proved the existence of pangea

A

wegners evidence of fossils and similar rock types indicating a large ice sheet
holmes idea of an ‘internal mechanism’ causing continental drift
marie tharps mapping of the ocean floor backing up the continental drift theory
hess’ idea of convection currents spreading plates
magnetism

67
Q

how was magnetism used to prove the theory of plate tectonics

A

the metal core creates a magnetic field
at mid ocean ridges minerals in magma align in direction of magnetic field forming a symmetric pattern on each side

68
Q

what is the slab pull mechanism(come back to)

A

convection currents stretch and weaken crust, magma is initially less dense than surrounding crust, as it cools it increases density causing it to move away from the ridge, denser oceanic plate is forced under continental plate

69
Q

what are the characteristics of continental plate

A

thicker, less dense, heterogeneous, oldw

70
Q

what are the characteristics of oceanic plate

A

thine, more dense, homogeneous, younge

71
Q

what are the three types of plate boundaries

A

converging- two tectonic plates move towards each other
diverging- two tectonic plates move apart from each other
transform- two tectonic places horizontally slide past each other

72
Q

what is a glacier

A

A large, perennial accumulation of crystalline ice, snow, rock, sediment, and often
liquid water that originates on land and moves down slope under the influence of
its own weight and gravity

73
Q

how much of the worlds freshwater is held in glaciers

A

70%

74
Q

why are glaciers important

A

source for water, agriculture and hydropower
indicate climate change
sea levels rising

75
Q

how is glacier ice formed

A

by firnification as snow accumulates and is compacted to fern then the expulsion of air, recrystalisation and compaction results in glacier ice

76
Q

what is the glacier mass balance

A

the annual balance between the accumulation of snow and the ablation of ice

77
Q

what is a positive glacier mass balance

A

accumulation > ablation = glacier advance

78
Q

what is a negative glacier mass balance

A

ablation > accumulation = glacier retreat

79
Q

what is the equilibrium line of a glacier

A

boundary between the accumulation and ablation zones
For a glacier in equilibrium mass balance, the accumulation
area ratio (AAR) = ~0.6

80
Q

what is the thermal regime of a glacier

A

refers to whether the ice at the base of a glacier is above or below melting
point, can be affected by pressure

81
Q

what is a warm based glacier

A

Ice is melting across the
glacier bed
Glacier moves by basal
sliding and/or soft-sediment
deformation
Glacier plucks and abrades

82
Q

what is a cold based glacier

A

Ice is frozen to its bed
Glacier moves by internal
deformation only
Erosion is insignificant: the
glacier protects the land
beneath

83
Q

glacier movement- internal deformation (creep)

A

Movement of ice within a glacier due to deformation of ice crystals under the stress of
glaciers weight
Cold based glaciers = frozen to bedrock, movement primarily in upper layers
Warm based = deformation is faster, partial melting at the base accommodating basal sliding

84
Q

glacier movement- basal sliding

A

The glacier slides over its bed because
of a lubricating film of meltwater
Pressure melting must be present
across wide areas of the glacier sole

85
Q

glacier movement- soft-sediment deformation

A

The glacier rides on a layer of
pressurised, water-saturated sediment.
Must be warm-based ice and presence
of multiple sediment layers

86
Q

how do glaciers erode landscape

A

with tools such as sediments, which are incorporated by plucking and quarrying
warm based are effective at eroding

87
Q

what are the three ways sediment is transported in a glacier

A

suparglacial- ncorporation at
glacier surface
englacial- Incorporation within
the body of a
glacie
basal- along the bed of a
glacier (plucking
and abrasion)

88
Q

what are glacial deposts

A

till or moraine

89
Q

what is a slopw failure

A

the irreversible loss of strength of
slope-forming materials

90
Q

what is a mass movement

A

the downslope movement of slope
material under the influence of the
gravitational force of the material itself
and without the assistance of moving
water, ice or air

91
Q

what is the equation for stability

A

resisting forces (Cohesion and
frictional strength of
the material) over driving forces (Gravity or other external
stresses trying to pull
material down a slope)

92
Q

what is normal stress

A

force holding the material to a slope and is determined by weight force and slope angle

93
Q

what does frictional strength depend on

A

frictional properties if the material, smooth on smooth = low frictional potential and rough on rough = high frictional potential

94
Q

how is strength providedd

A

by cohesion
eg by electrostaic and molecular forces
cement
roots

95
Q

what is the influence of water on a slope

A

add extra weight and changes cohesion as well as reduces the frictional strength through buoyancy

96
Q

what is the effect of having saturated soil

A

water pushes particles in apart changing where weight is concentrated

97
Q

what is the effect of earthquakes on slope stability

A

shaking induced temporary, cyclic increases in driving stress and reduction in resisting stresses

98
Q

what is the factor of safety used to measure

A

how close a slope is to failure and describes the balance of forces acting on a slope

99
Q

what is the simple equation for the factor of safety

A

F= shear resistance/shear force

100
Q

what are all the elements involved in factor of safety

A

cohesion of rocks/soil
weight of a slope
angle of a slope
pore water pressure
angle of internal friction

101
Q

where does the shear plane develop

A

when the two lines on a graph for shear strength and shear stress cross

102
Q

how is a slopes stability defined if the factor of stress is greater than 1.3

A

stable- major events and long term environmental changes needed to cause hazard

103
Q

how is a slopes stability defined if the factor of stress is between 1.0-1.3

A

conditionally stable- minor triggering event needed

104
Q

how is a slopes stability defined if the factor of stress is less than 1.0

A

actively unstable- imminent failure

105
Q

what are the four mass movement processes

A

falls
topples
slides rotational and transnational
flows

106
Q

what is a fall

A

collapse of material from a cliff of steep slope

107
Q

what is a topple

A

forward rotational movement of rock

108
Q

what is a rotational slide

A

failure of material at depth then movement by sliding along surface

109
Q

what is a transnational slide

A

the down-slope movement occurs along a weakness

110
Q

what is a flow

A

the movement of material in the form of a fluid

111
Q

what are the three fundamental processes of material motion

A

pure flow- thin layers sliding over each other
pure slide- slip of a rigid block moving at the same velocity
pure heave- up and down movement of individual particles

112
Q

what is laminar water flow

A

layers of water of molecular thickness slide over each other, curved velocity profile shows surface water travels fastest

113
Q

what is turbulent water flow

A

chaotic eddies produce irregular paths and variable velocities

114
Q

what is lift force (bernoulli effect)

A

convex surface of grain acts like aeroplane wing so flow has to accelerate
=low pressure above particle
=lift force
once lifted particles are entrained into turbulent eddies and carried downstream

115
Q

After being entrained, how are particles transported

A

1.Rolling along the
bed (bedload)
2. Sliding along the
bed (bedload)
3. Bouncing along
bed i.e. saltation
(bedload)
4. Suspended in
water column
(suspended load)
5. Dissolved mineral
and organic matter
(solute load)

116
Q

what are the factors that effect a channel form

A

valley slope- steep or gentle
sediment supply- high or low
sediment supply- coarse or fine
water discharge variation- high or low

117
Q

what is a characteristic of meandering rivers

A

deposition on inner beds (slow moving water), erosion on outer beds (at thalweg)

118
Q

what are braided rivers

A

network of river channels separated by sediment bars
mid channel bars
flood channels
chutes

119
Q

what is lanes balance

A

Erosion and deposition based on the balance between aggradation and discharge rate

120
Q

what happens if the < Sediment load and/or > discharge

A

=degradation (erosion)

121
Q

what happens if > Sediment load and/or < discharge

A

=aggradation (deposition)

122
Q

what is aggradation caused by

A

decrease in discharge
increase in sediment load
increase in grain size
decrease in slope

123
Q

characteristics of a wave

A

wave particles move in circular (orbital) motions
crest is the highest part
trough is the lowest
distance between in wavelength

124
Q

what slows a wave and shortening its wavelength

A

frictional between orbital motions and seabed

125
Q

what happens when wave energy is compressed

A

increase in height
water becomes too shallow to sustain wave height at H/L= 1/7, thus breaking waves

126
Q

what is the difference between summer and winter waves

A

summer waves deposit as a bern and winter waves erode that and deposit it as a longshore bar

127
Q

what is the swash

A

forward movement of
water as wave breaks

128
Q

what is the backwash

A

movement of water
towards ocean

129
Q

what is shore normal

A

water flows
directly towards beach: sediment
transported up and down the
beach rather than along it building
features like berms

130
Q

what is longshore drift

A

approaches
shore at oblique angle, transport
sediment along shore creating
spits and sandbars

131
Q

constructive waves

A

swash>backwash = sediment moves up beach

132
Q

destructive waves

A

swash<backwash = sediment moves down beach

133
Q
A

EV11001 (2 decks)

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