Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Geography HL > D.1 - Geophysical Systems > Flashcards

D.1 - Geophysical Systems Flashcards

You may prefer our related Brainscape-certified flashcards:
U.S. Geography flashcards World Geography flashcards
1
Q

What are the 3 main parts of the earth and what sections fall into these

A
  1. Mantle
  2. Outer core
  3. Inner core
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the mantle

A

Semi solid rock sourounding the core. More solid closer to the surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the core

A

Centre of the earth
Very high temp
Rock material is melted into flowing liquid
Inner core is hottest but is solid due to pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the 2 main flows of heat from earths interior to the surface

A

radiogenic (that is, radioactive decay of materials in the mantle and the crust)

primordial heat (that is, the heat lost by the Earth as it continues to cool from its original formation).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the 3 ways earths heat transport occurs

A

Earth heat transport occurs by:
- convection
- conduction
- volcanic advection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How does a large scale convection current occur in earths interior

A

Hot magma rises through the core to the surface and then spreads out at mid-ocean ridges. The cold solidified crust sinks back into the Earth’s interior because it is heavier and denser than the surrounding material. The cause of the movement is radioactive decay of uranium and potassium in the mantle.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Define subduction

A

Subduction refers to the plunging of one plate beneath another.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

When does a subduction zone form (explain in 4 parts)

A
  1. Subduction zones form where an oceanic lithospheric plate collides with another plate - whether continental or oceanic.
  2. The density of the oceanic plate is similar to that of the aesthenosphere, so it can be easily pushed down into the upper mantle.
  3. Subducted (lithospheric) oceanic crust remains cooler, and therefore denser than the surrounding mantle, for millions of years; so once initiated, subduction carries on, driven, in part, by the weight of the subducting crust.
  4. The subducting plate drags or pulls the rest of the plate behind it. Plates are hot at the mid-ocean ridge but cool as they move away.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Define plume

A

A plume refers to a small area of unusually high heat flow. Plumes or hotspots can cause movement, that is, the outward flow of viscous rock from the centre may create a drag force on the plates and cause them to move.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Where are plumes found

A

Most plumes are found near plate margins and they may be responsible for the original rifting of the crust. However, the world’s most abundant source of lava, the Hawaiian Hotspot, is not on the plate margin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Where does rifting occur

A

Rifting occurs at constructive plate boundaries, for example the East Africa Rift Valley or the rift at Thingvellir, Iceland, where the North American Plate and the Eurasian Plate are moving away from each other.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the mian cause of rifting

A

In each case, hotspot activity is believed to be the main cause of rifting. The rift valleys created consist of rock that is hotter and less dense than the older, colder plate. Hot material wells up beneath the ridges to fill the gaps created by the spreading plates.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What rocks make up the crust

A

Sial and sima

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe sial

A

Lighter rocks in the upper crust . Makes up the continents

It’s composed of silicates and aluminium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe sima

A

Heavier rock in lower crust. Makes up ocean beds

Composed of silicates and magnesium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe tectonic plates

A
  • make up the crust
  • move, carried by currents moving slowly by liquid mantle
  • dragged over the asthenosphere in different directions
  • float as they are less dense
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are 3 causes of plate movement

A
  • convection currents
  • ridge push
  • slab pull
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How does a convection current cause plate movement

A
  • Occur in mantle due to radioactive decay of elements in upper mantle, which releases heat
  • Allow the earth to dissipate heat from its hot core
  • Temperature rises so liquid rocks expand and rise to surface, forming currents
  • Upward movement occurs where there is the greatest radioactive decay, which is unevenly distributed according to the composition of the earth
  • Heat rises from the core and spreads at the mid-Atlantic ridges
  • This causes them to pull apart
  • The cold solid crust sinks as it is denser than the surroundings
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How does a ridge pull cause plate movement

A
  • occurs at mid ocean ridges at divergent plate boundaries
  • due to rigid lithosphere sliding down hot, raised asthenosphere between the ridges
  • gravitational forces slide the lithosphere away from the high ridge towards subduction zones
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How does slab pull cause plate movement

A
  • tech tonic plate motion caused by its subduction
  • cold, dense slabs of plates sink deep into the mantle
  • this pulls on the rest of the plates
  • occurs at convergent margins at the subduction zones
  • reduces pressure on underlying asthenosphere, which leads to partial melting
  • the resulting magma wells up under divergant margins, cools, and rises
  • it is added to the plate as new lithosphere
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are the 3 types of plate boundaries

A
  • divergant/ constructive
  • convergent/ destructive
  • transform/conservative
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the movement of a divergant plate

A

Spread apart, creating new material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What causes a divergant plate boundaries

A

They are formed by plumes pushing plates apart

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What does divergant plates create

A

New oceanic crust is added as pillow lava
Also occurs as rift valleys where continents are splitting apart

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is the lava flow of a divergent plate

A

Magma rises through shallow crust and results in low silica effusive lava
Creates low viscosity, basaltic flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What volcanos do divergent plate boundaries create

A
  • gentle sloping/shield volcanos
  • erupt with regular and continuous frequency
  • associated with Icelandic and Hawaiian eruptions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is the movement and result of convergent plates

A

They collide into each other and cause the destruction of material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What processes do convergent plate boundaries create

A
  • subduction can occur leading to the partial melting of mantle as saturated oceanic crust enters it
  • part of crust melts too, causing magma to rise up
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is the lava flow in a convergent plate

A
  • magma rises through more crust and results in high sill a magma
  • creates high viscosity andesitic magma
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What volcanos do convergent plate boundaries create

A
  • forms composite cone volcanos
  • magma produces tephra and pyroclastics
  • associated with vulcanícele and plinian eruptions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is the movement and result of a transform plate boundary

A

They slide laterally and do not create nor destroy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What does a transform plate boundaries create

A

Earthquakes as the plates move past each other and generate friction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Summarise the subduction zone

A
  • region of crust where tectonic plates meet
  • the oceanic crust usually sinks into the mantel beneath light continental crust
  • earthquakes are a common feature
  • sima is cooler/denser than asthenosphere
  • its downward movement experts drag on the asthenosphere causing fricación and therefore earthquakes
  • the plate is forced down and heated up by the surrounding mantle
  • eventually malts, giving off gasses with rise tp the surface as liquid rock
  • this is released as a volcanic eruption
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What are the 3 types of collisions between plates of different material

A
  • sial + sial
  • sima + sima
  • sial + sima
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is the collision between a sial + sial plate

A

This is light continental material with similar density. At this collision folding will occur as plates crumple into each other and are forced upwards forming mountain ranges

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What is the collision between a sima and sima plate

A

Here heavy oceanic material with similar density will collide causing both plates to subduction forming deep ocean trenches

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What is the collision between a sial and sima plate

A

Here one sial and one sima plate collide with different density’s causing the denser sima plate to subduct. The lighter sial plate will fold and fault upwards against the other plate forming a volcano.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Define magma

A

Molten rock found beneath earths surface, stored int he crust

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Define lava

A

magma that reaches the surface of the earth through a volcano vent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Define tephra

A

solid rock material ejected by volcanic eruptions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

What are the 2 types of lava

A

• Andesite/dacite - silica rich lava which is more viscous, generally erupt more explosively
• Basaltic - runny and relatively fluid lava which contains less silica

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What are the 3 types of volcano

A
  • cinder cone
  • composite cone
  • shield
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What plate boundarie does a cinder cone volcano occur at

A

Any of them - occurs whenever magma gets near surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

What plate boundaries does a composite cone volcano occur at

A

Convergent - where oceanic crust subducts beneath continental

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

What plate boundaries does a shield volcano occur at

A

Divergant or hot spot

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

What is the shape of a cinder volcano

A

Steep, straight sides
Cone-shaped hill
Much smaller
Bowl-shaped crater at summit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

What is the shape of a composite cone volcano

A

Steep, upwardly concave sides
Much taller
Have a central vent or cluster of vents at summit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

What is the shape of a shield volcano

A

Gentle slope
Looks like shield resting on ground
Very low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

What is a cinder volcano composed of

A

Layers of ash deposited from successive explosive eruptions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

What is a composite cone volcano composed of

A

Alternating layers of hardened lava and proclastic material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

What is the process of formation for a cinder cone volcano

A

Occur when mix of gases and magma rise to surface and blow violently into air
Lava is blasted into tiny fragments which solidify as ash and cinders
Form symmetrical cone around the crater
Constructed of loose tephra

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

What is the process of formation for a composite cone volcano

A

Formed as eruptions spew out and deposit combinations of ash lava, pumice, and tephra at various times, forming a cone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

How is lava ejected from a cinder cone volcano

A

Eject basaltic lava
Relatively thick with trapped gases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

What is the process of formation for a composite cone volcano

A

Formed as eruptions spew out and deposit combinations of ash lava, pumice, and tephra at various times, forming a cone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

What is the lava flow from a composite cone volcano

A

Eject gas-rich andesitic lava

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

What is the lava flow from a shield volcano

A

Very fluid basaltic lava
Travels long distances before solidifying

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

What is the eruption process of a cinder cone volcano

A

Often produce lava flows from base

58
Q

What is the eruption process for a composite cone volcano

A

Produce lava flows and proclastic materials
Produce large eruptive columns which inject gases and particles high into atmosphere
Associated with lahars and lava flows

59
Q

What is the eruption process for a shield volcano

A

Produce lava flows and proclastic materials
Produce large eruptive columns which inject gases and particles high into atmosphere
Associated with lahars and lava flows

60
Q

What is a Strombolian eruption

A

Strombolian eruptions are explosive eruptions that produce proclastic rock. Eruptions are commonly marked by a white cloud of steam emitted from the crater. Frequent gas explosions blast quantities of runny lava into the air, and when these settle and cool they form the cone.

61
Q

What is a Vulcanian eruption

A

Vulcanian eruptions are violent and occur when the pressure of trapped gases in viscous magma becomes sufficient to blow off the overlying crust of solidified lava. Often the eruption clears a blocked vent and spews large quantities of volcanic ash into the atmosphere. Violent gas explosions blast out plugs of sticky or cooled lava. Fragments build up the cone of ash and pumice.

62
Q

What is a Vesuvius eruption

A

Vesuvian eruptions are characterized by very powerful blasts of gas that push ash clouds high into the sky. Lava flows also occur. Ash falls to cover the surrounding area.

63
Q

What is a plinian eruption

A

Plinian eruptions are extremely violent eruptions characterized by huge clouds of pulverized rock and ash that are kilometres thick. Gas rushes up through the sticky lava and blasts ash and fragments into the sky in huge explosions. Gas clouds and lava can also rush down the slopes. Part of the volcano may be blasted away during the eruption.

64
Q

What are the 3 primary hazards of a volcano

A
  1. Pyroclastic flows
  2. Pyroclastic surges
  3. Lava flows
65
Q

What is a Pyroclastic flow

A

Fast mixtures of lava, pumice, ash, and gases extruded from volcanoes during eruptions
Flow downhill, blown by high pressure gases from the eruption
Destroys everything in their path, either by burning, knocking over, shattering, or burying

66
Q

What is a Pyroclastic surge

A

Fast clouds of hot ash that travel with proclastic flows

Fall back to earth as they cool, covering vast areas with a layer of ash

67
Q

What is a lava flow

A

Occur when molten rock pours and oozes from erupting volcanoes
Cools and solidifies as it flows across ground
Typically not too dangerous, as molten lava is so viscous it flows slowly
However, can be hard to stop or divert
Significant threat to property

68
Q

What are 5 secondary hazards of a volcano

A
  • Lahars
  • landslides
  • floods
  • fires
  • tsunamis
69
Q

What are Lahars

A

Liquid mudflow made of a slurry of pyroclastic materials, rocks, and water
Typically flow down sides of volcanoes
Move quickly, destroying everything in its path Especially prominent in cold areas where eruptions melt snow/ice which gather extra material as they flow downhill

70
Q

What are landslides

A

Large rock/soil masses separate from sides of mountains and slip downhill due to gravity Can be initiated by earth tremors/quakes, leakage of gases beneath the ground, or explosive equations
Occur very quickly

71
Q

What is a Strombolian eruption

A

Strombolian eruptions are explosive eruptions that produce proclastic rock. Eruptions are commonly marked by a white cloud of steam emitted from the crater. Frequent gas explosions blast quantities of runny lava into the air, and when these settle and cool they form the cone.

72
Q

What is a Vulcanian eruption

A

Vulcanian eruptions are violent and occur when the pressure of trapped gases in viscous magma becomes sufficient to blow off the overlying crust of solidified lava. Often the eruption clears a blocked vent and spews large quantities of volcanic ash into the atmosphere. Violent gas explosions blast out plugs of sticky or cooled lava. Fragments build up the cone of ash and pumice.

73
Q

What is a Vesuvius eruption

A

Vesuvian eruptions are characterized by very powerful blasts of gas that push ash clouds high into the sky. Lava flows also occur. Ash falls to cover the surrounding area.

74
Q

What is a plinian eruption

A

Plinian eruptions are extremely violent eruptions characterized by huge clouds of pulverized rock and ash that are kilometres thick. Gas rushes up through the sticky lava and blasts ash and fragments into the sky in huge explosions. Gas clouds and lava can also rush down the slopes. Part of the volcano may be blasted away during the eruption.

75
Q

What is a mantle plumes

A
  • Mushroom-shaped zones within the mantle consisting of abnormally hot material
  • Form where radioactive decay is particularly strong
  • Not associated with plate boundaries
  • So hot that they tend to rise and spread out in asthenosphere beneath the crust, as a geological intrusion forcing overlying crust upwards
76
Q

What are some hotspots

A

• Areas above plumes, fed by underlying mantle
• Anomalously hot compared with surrounding mantle
• E.g. Hawaii is far from plate boundaries but is situated on a hot spot o Still has many active volcanoes
• As the Pacific Plate passes over the hot spot, new volcanoes are created

77
Q

Define earthquake

A

An earthquake is a series of seismic vibrations or shock waves which originate from the focus - the point at which the plates release their tension or compression suddenly (Figure D.5). The epicentre marks the point on the surface of the Earth immediately above the focus of the earthquake.

78
Q

What is a shallow focused earthquake
- where are they found
- what is there affect

A

Shallow-focus earthquakes occur relatively close to the ground surface, whereas deep-focus earthquakes occur at considerable depth under the ground. Shallow-focus earthquakes have greater potential to do damage as less of the energy released by the earthquake is absorbed by overlying material.

79
Q

How can a large earthquake be predicted

A

A large earthquake can be preceded by smaller tremors known as foreshocks and followed by numerous aftershocks.

80
Q

What are the 2 shock wave types

A
  • body wave
  • surface wave
81
Q

What are body waves §

A

Body waves are transmitted upwards towards the surface of the earth from the focus of the earthquake

82
Q

What are the 2 types of shockwave

A
  • primary and secondary
83
Q

What is a primary shock wave

A

Primary (P) waves or pressure waves are the fastest and can move through solids and liquids - they shake the earth backwards and forwards.

84
Q

What is a secondary shock wave

A

Secondary (S) waves or shear waves move with a sideways motion and are unable to move through liquids - they make the ground move horizontally, causing much damage.

85
Q

What are the 2 surface waves

A
  • love wave
  • Rayleigh wave
86
Q

What’s does a love wave do

A

Cause the ground to move sideways

87
Q

What does a Rayleigh wave do

A

Cause the ground to move up and down

88
Q

How do love and Rayleigh waves move

A

Love waves and Rayleigh waves travel slowly through the crust, but they cause the most damage.

89
Q

What is the contrast between body and surface waves

A

P-waves and S-waves are transmitted from the earthquake focus to the surface. By contrast, surface waves are produced in the ground by the transformation of some body waves once they reach the surface.

90
Q

What is the focus/hypocentre

A

Point of fracture where stored seismic energy is released from when a break occurs

91
Q

what is the epicentre

A

Point on earth’s surface directly above focus

92
Q

What is the fault line

A

Break in the ground occurring when tectonic plates move
Are areas where EQs are likely

93
Q

What is wave motion

A

When crust ruptures, seismic waves move outwards in all directions
Shocks waves usually quickly dissipate, as the crust is so dense
Generates three types of waves during an EQ

94
Q

What is the speed ranking on waves

A

Primary - fastest
Secondary - second fastest
Surface - slowest

95
Q

What is the frequency ranking on waves

A

Primary and secondary - high - cause low buildings to vibrate
Surface - low - cause high buildings to vibrate

96
Q

What are the 2 types of boundaries

A
  • shallow focus
  • deep focus
97
Q

Where are shallow boundaries found and what do they do

A
  • transform/divergant
  • cause extensive damage due to little depth of rock to absorb seismic energy
98
Q

Where are deep focus found and what do they do

A
  • Convergent
  • Occur as mountains are built up through folding and faulting, or subduction as oceanic plate is forced under continental
99
Q

What stress is found at convergent plate boundaries

A
  • compression
  • meaning they push together
  • found at a normal fault
100
Q

What stress is found at a divergant plate boundary

A
  • tension
  • meaning they pull away from each other
  • this is found at a fault which is reversed or thrust
101
Q

What kind of stress is found at a transform plate boundary

A
  • shear
  • push in opposite directions
  • found at a strike - slip fault
102
Q

What are seismic belts and what are the 2 types

A

• Narrow geographic zones on surface where most EQ activity occurs
• Broad belts - associated with convergent boundaries and subduction zones
• Narrow belts - associated with divergent boundaries

103
Q

What are 3 human causes of earthquakes

A
  • large dams in earthquake prone areas
  • mining
  • fracking
104
Q

How does dams cause earthquakes

A

Weight of water places downward pressure on fault lines beneath
Water can seep down and lubricate rock movement
Over time, stresses in fault line build up
Can destabilise them

105
Q

How does mining cause earthquakes

A

Removal of material from ground can cause instability
Leads to sudden collapses that trigger EQs

106
Q

How does fracking cause landslides

A

Directly from drilling/blasting/excavating
Disposal of high-pressure wastewater can crack rocks and lubricate faults

Fracking (also known as hydraulic fracturing) is a process in which water, containing certain chemicals, is injected at very high pressure into rocks in order to open up their pore spaces and release natural gas contained within the rocks. Fracking has been associated with the triggering of earthquakes in the UK.

107
Q

What are 3 secondary hazards of earthquakes

A
  • landslides
  • liquefaction
  • tsunamis
108
Q

Why are landslides a secondary hazard of earthquakes

A

EQs create stresses which can make weak slopes fail and dislodge rocks
Can even cause a new fault to fracture the hillside
Huge rock masses may slide downhill and destroy everything in its path
Accompanied by a destructive rush of air

109
Q

Why is liquefaction a secondary hazard of earthquakes

A

EQs shake an area of soil and separate its solid and liquid components
Causes it to lose structural integrity and behave like a liquid, flowing downhill
Causes collapse of areas with a soil foundation

110
Q

Why are tsunamis a secondary hazard of earthquakes

A

Very large sea surface waves caused by underwater EQs/landslides and volcanic activity
After the shock, waves travel outwards in all directions
In the open ocean they travel extremely fast but are not felt
Approaching coasts, they slow down and increase in amplitude, affected by submarine topography
Lead to severe damage and death
Most death is from drowning
Includes secondary risks like flooding, contamination of drinking water, fires from ruptured gas lines, and loss of infrastructure
Can be monitored by networks of tidal gauges which provide countries with warning messages

111
Q

define mass movement

A

Downslope movement of weathered rock materials due to gravity

Occurs to establish an equilibrium between weathering and erosion on sloping ground

Occurs when equilibrium is disturbed as:
- Weathering material accumulates on upper slope faster than it can be transported away by agents of erosion
- Agents of erosion undercut weathered materials

• Causes rocks to break free and tumble downwards due to pull of gravity

• Soils/weathered rocks are more vulnerable than bedrock as they are held together more loosely

• Contains many types which are not always separate

• Can easily transition into different forms as environment changes

112
Q

What are 4 factors which promote mass movement

A
  • water
  • initial impetus
  • texture
  • slope
113
Q

How does water promote mass movement

A

Rainfall adds weight to weathered material and disrupts equilibrium
Water lubricates rocks and soil particles, destroying cohesion
Water pushes particles apart by exerting pressures on spaces between them

114
Q

How does initial impetus promote mass movement

A

Triggering events upset equilibrium
May be physical (e.g. EQs, rainfall) or human (e.g. blasting for roadworks/mining)
Can even be caused by lightning, trains, gun shots, burrowing animals, removing vegetation etc.

115
Q

How does texture promote mass movement

A

Coarser, rougher particles resist mass movement more effectively than smooth particles, as they have more opposing frictional forces

116
Q

How does slope promote mass movement

A

Gravity works more effectively on steeper slopes, so mass movements is more rapid
Erosion of slope bases steepen them, increasing the gravitational forces, disrupting equilibrium, and thus initiating mass movement

117
Q

What are the four processes of each a deform of mass movement

A
  • creep
  • flow
  • slides and falls
  • subsidence
118
Q

What are the three process of creep

A
  • creep
  • terrace totes
  • rock/talus creep
119
Q

What is creep

A

Slow downhill movement of surface material due to gravity
Continuous movement
Too slow to see with the eye
Posts/poles/walls develop a marked lean
Tress develop bent trucks as their roots shift downhill

120
Q

What is terracettes

A

Form when saturated soil on steep slopes expand during rain, then contract as it dries Causes small steps to form which dislodge from underlying soil and move downhill from gravity

121
Q

What is rock/talus creep

A

Under gravity, talus slopes are formed at the foot of steep slopes that have shed talus If talus slopes become steeper than their critical angle, equilibrium is lost and mass movement will occur to restore it

122
Q

What are 3 types of rapid flow

A
  • earthflows
  • mudflows
  • debris avalanches
123
Q

What are earthflows

A

Like slow moving landslides
Occur on slopes when earth is saturated with water and becomes capable of slow flowage
Usually too slow to see
Leave scars on hillside, usually marking a point where it began
Broaden out to a wider slump of earth at the foot of the slope

124
Q

What are mud flows

A

Occur when heavy rains destabilise a slope and cause soil/rocks/boulders to slide downhill
Deserts - develop alluvial fans at foot of slope
Mountains - occur on steep slopes when sudden thaw melts snow
Volcanic areas - known as lahars, occurring commonly on loose cinder cone slopes

125
Q

What are debris avalanches

A

Occurs mainly in alpine areas
Leaves significant scars on slopes of mountains

126
Q

What is solifluction

A

In permafrost areas, upper ground layer is permanently saturated as water cannot soak away
The resulting slushy material moves down, even on very gentle slopes

127
Q

What are 2 types of slides and falls

A
  • landslides
  • rockfalls
128
Q

What are landslides

A

Rapid sliding and slipping movement of large bedrock masses
Large rocks tumble downhill and break into smaller talus
Usually down steep slopes or along a fracture plane
Occur when a slip surface develops and there is a lack of support for a large section of land
Slide surface may be a curved shear surface, producing slumps, or a planar shear surface, causing rockslides

129
Q

What are rockfalls

A

Even quicker than landslides
One or a few large rocks separate from the slope and drop down
Roll rapidly down after their vertical fall
Accumulate at foot of slope as talus

130
Q

What are three types of subsidence

A
  • subsidence
  • cover subsidence sinkholes
  • cover collapse sinkholes
131
Q

What is subsidence

A

Downward settling of material with little horizontal movement
Occurs when material is removed fron beneath the surface
E.g. due to erosion by underground streams, rocks like limestone dissolving, or mining
Can also occur when groundwater is pumped out for human use, reducing hydraulic pressure of the aquifer
Localised subsidence forms sinkholes

132
Q

What is cover subsidence sink holes

A

Form slowly over decades to centuries
Occurs as soil is transported by drainage channels into an underground reserve like a cave
Cause gradual downward sinking of land
Can damage building foundations, but there is normally enough warning of movement to repair/renovate the buildings

133
Q

What are cover collapse sinkholes

A

Appear seemingly without warning - very dangerous
Occur during heavy rain when clay or sandstone particles beneath surface are saturated, causing their glue-like cohesion to disintegrate suddenly and cause a sinkhole
Also develop when roof of underlying caves collapses
E.g. if seepage dissolves underground limestone and collapses suddenly
Can also result from human actions that cause ground collapse, like mine collapses, pipeline breaks, or groundwater over-extraction

134
Q

What 2 factors cause slope failure

A

• a reduction in the internal resistance, or shear strength, of the slope
• an increase in shear stress - that is, the forces attempting to pull a mass downslope.

135
Q

What are 5 factors leading to increased shear stress

A
  • removal of lateral support through undercutting to slope steepening
    Erosion by rivers and glaciers, wave action, faulting, previous rockfalls or slides
  • removal of underlying support
    Undercutting by rivers and waver, subsurface solution, loss of strength by exposer of sediment
  • loading of slope
    Weight of water, vegetation, accumulation of debris
  • lateral pressure
    Water in cracks, freezing in cracks, swelling, pressure release
  • transient stresses
    Earthquakes, movement of trees in wind
136
Q

what are 4 factors leading to reduction in shear stress

A
  • weathering effects
    Disintegration of granular rocks; hydration of clay minerals; chemical solution of minerals (that is, the weathering of certain chemicals, notably calcium carbonate), in rock or soil
  • changes in prone water
    Saturation, softening of material pressure
  • changes of structure
    Creation of fissures in clays, remoulding of sands and clays
  • organic effects
    Burrowing of animals, decay of roots
137
Q

When was the landslide in Nepal

A

2015

138
Q

Why is Nepal prone to landslides

A

Landslides are common in Nepal. The region, with its young geology, seismic activity, steep slopes and intense cloudbursts, has a history of earth-moving events. Factors that trigger landslides include seasonal rainfall, road construction and slopes weakened by previous slides.

139
Q

What earthquake caused these earthquakes

A

The Gurkha earthquake of April of 2015

140
Q

What was the largest landslide in Nepal

A

One of the largest was an ice and rock avalanche at Langtang. This caused substantial loss of life as entire settlements were buried. The landslide consisted of a large mass of freefall rock and ice, shearing off more rock on its descent.
The vertical distance was 700-800 m over a horizontal distance of 2-3 km. The valley below was severely obstructed and covered by debris. It looks like the threat of landslides will continue to exist in this impoverished and vulnerable country.

Geography HL (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions