Paper 1 - Section A - Tectonic Processes and Hazards Flashcards
1
Q
Define a hazard
A
A potential threat to human life and property
2
Q
Define a disaster
A
An event which has effected people or civilisation in any way
3
Q
Where are tectonic hazards distributed around the world? (Think plate boundary types etc) — and consider anomalies!!
A
Earthquakes:
- predominantly convergent plate boundaries
- intraplate tectonics: central plate activities which occurs due to weaknesses in the crust
Volcanoes:
- predominantly around convergent plate boundaries
- hotspots: in the centre of plates where hot molten material breaks its way through weakened crust
- pacific ring of fire
4
Q
What are the names of the 7 major plates?
A
- African plate
- Antarctic plate
- Eurasian plate
- Pacific plate
- Indo-Australian plate
- North American plate
- South American plate
5
Q
What are the names of the 7 minor plates?
A
- Arabian plate
- Caribbean plate
- Cocos plate
- Nazca plate
- Juan de Fuca plate
- Philippine sea plate
- Scotia plate
6
Q
List the changes in the trends of tectonic activity since the 1960s in terms of frequency of events, number of fatalities / costs etc
A
- total number of recorded hazards has increased
- number of fatalities has decreased
- total number of people being affected by the hazards has increased due to population growth
- economic costs associated with hazards has increased
7
Q
What makes reporting disaster impacts difficult?
A
- depends on whether direct or indirect deaths are recorded
- location: rural / isolated areas hard to get data from
- different methods / sources document different statistics
- number of deaths stated by governments subject to bias
8
Q
Starting from the innermost section, name the 4 sections within the earths structure
A
- Inner core:
- Over 5000km below earths surface
- solid due to high pressure
- Outer core:
- over 2900km below earths surface
- dense semi molten rock
- Mantle (asthenosphere):
- over 700km below earths surface
- semi molten
- convection currents due to temperature gradient
- Crust (lithosphere):
- thinnest, lightest, uppermost layer of earth
- oceanic crust: 7km thick
- continental crust: 70km thick
9
Q
Describe the landforms a convergent plate margin creates
A
Continental + continental:
- fold mountains
- earthquakes
Continental + oceanic
- fold mountains
- earthquakes
- volcanoes
Oceanic + oceanic:
- ocean trenches
- island arcs
- earthquakes
- volcanoes
10
Q
Describe the landforms a divergent plate margin creates
A
Continental + Continental:
- rift valleys
- volcanoes
Oceanic + oceanic
- ocean ridges
- volcanoes
11
Q
Describe the landforms a conservative plate margin creates
A
- earthquakes
12
Q
Define Benioff zone
A
A seismically active underground area with a subduction zone
13
Q
Describe the process of mantle plumes occurring i.e Hawaii island arc
A
- Hot magma rises through weak parts of the oceanic lithosphere (melts it) which forms new volcanic island
- As tectonic plate moves over stationary hotspot / plume, volcano shifts along
which forms a new volcanic island - A chain of volcanic islands are created (island arcs)
The further down the chain, the more old / extinct / eroded they become
14
Q
Describe the 5 stages of mantle convection
A
- The core heats up the magma within mantle
- Hot mantle becomes less dense — RISES
- As it travels further from the heat source, it cools — becomes LESS DENSE
- It then begins to sink
- The cycle repeats!
(Takes place within the asthenosphere)
15
Q
Define paleomagnetism
A
Study of past changes in earths magnetic field
16
Q
Describe the process of paleomagnetism I.e mid Atlantic ridge
A
Every 400,000 years or so, the earths magnetic fields change direction (poles swap)
Scientists discovered same pattern of magnetic direction on either side of the ridge (can only happen if new rock got formed at the same time on both sides)
(Sea floor progressively ages, the further it is from the ridge)
17
Q
Describe the process of sea floor spreading, and what landforms can it create?
A
Occurs at mid ocean ridges, where new oceanic crust is formed through volcanic activity
Which then gradually moves away from the ridge
Hot magma gets forced through asthenosphere before hardening; forming new ocean crust
OCCURS AT DIVERGENT PLATE BOUNDARIES
(Plates pushed apart by hot magma, forming new oceanic crust: mid ocean ridges, underwater mountain ranges)
18
Q
Describe the process of subduction
A
This is when one plate sinks beneath another at a convergent boundary
As oceanic + oceanic or continental + oceanic plates move towards each other, one slides underneath and meets at a subduction zone
(Despite seafloor spreading the earth isn’t expanding, as new crust is being formed in a location it’s being destroyed in another)
(Zone where lithosphere is recycled back into the mantle at the surface, the subduction zone coincides with the bottom of the trenches)
19
Q
Describe the process of slab pull
A
Pulling forces exerted by cold, dense oceanic plate plunges them into the mantle due to their density and weight
(Aka subduction)
Newly formed oceanic lithosphere at mid ocean ridges are less dense than the asthenosphere (becomes denser as it ages) — sinks into mantle at subduction zones, pulling lithosphere slabs apart (divergent boundaries)
The descending plate which is pulled into the asthenosphere melts
20
Q
At what plate margins does mantle convection occur?
A
- divergent
- convergent
21
Q
At what plate margins does paleomagnetism occur?
A
- divergent
22
Q
At what plate margins does sea floor spreading occur?
A
- divergent
23
Q
At what plate margins does subduction occur?
A
- convergent
24
Q
At what plate margins does slab pull occur?
A
- divergent
25
What are the 3 types of earthquake waves?
1. Primary waves
2. Secondary waves
3. Love waves
26
Which 2 earthquake waves are known as body waves and which is known as a surface wave?
Body waves: (travel through earths body)
- primary 8km/s; travels through solids, compressional, vibrates in direction of travel
- secondary 4km/s; travels only through solid rocks, vibrates at right angles to direction of travel, large amplitude
Surface wave: (travel through earths surface)
- love: higher amplitude / most destructive; near to ground surface, rolling motion movement, large amplitude
27
What are the differences between the two types of crust?
Oceanic: high density — 3.0mg/m^3, mainly basalt, thin, new
Continental: low density — 2.6mg/mg^3, mainly granite, thick, old
28
Define hypocentre
Point within the earth where an earthquake rupture starts
29
Define epicentre
Point on the earths surface directly above the hypocentre
30
Secondary hazards: what is the process of soil liquefaction?
It affects poorly compacted sand and silt
1. Moisture in the ground separates from the soil particles and rises to the surface making it waterlogged (due to the large tremors)
2. Shaking destabilises the soil by increasing the space between the grains
3. This can cause the soil to behave like a liquid and loses its strength, which can cause building subsidence or landslides
31
Secondary hazards: how do landslides occur?
1. Earthquake tremors can weaken / damage cliff faces, hills and snow material
2. In consolidated material or loose rocks can collapse
3. Landslides can travel several miles and accumulate sediment along tour way
Risk varies with topography, rainfall, soil and land use
32
What are the 5 stages to a tsunami?
1. Earthquake causes fault or plate boundary to jolt at the seabed, causing a column of water to vertically displace
2. Gravity pulls this water back down, transferring the energy through the water in the form of a wave
3. The water travels outwardly at a fast pace yet a low amplitude (height)
4. As this water approaches the coast, the seabeds get shallower creating friction between the bed and the waves
5. This causes the water to slow down and gain height, creating a wall of water that can reach 100ft
33
Which type of zones are tsunamis typically created?
Subduction zones (convergent plate margins)
I.e pacific ring of fire
34
Define a wave train
A succession of similar tsunami waves at equal intervals
35
What varies the impact of a tsunami?
- population density
- coastal defences
- duration of the event
- wave amplitude and distance travelled
- warning / evacuation systems
- level of economic development
36
Name 4 primary hazards as a result of a volcano
1. Lava flows
2. Pyroclastic flows
3. Tephra and ash flows
4. Volcanic gases
37
What are lava flows?
Streams of lava which have erupted onto the earths surface — fast flowing lava can be dangerous (depends on viscosity)
Explosiveness and viscosity depends on it’s silicon content
38
What are pyroclastic flows?
Mixture of hot rock, lava, ash and gases which move very rapidly along the earths surface — extremely dangerous
39
What is tephra / ash flows, and it’s impact on surrounding buildings?
When pieces of volcanic rock and ash are blasted into the air — can seriously damage buildings which collapse under their weight
40
What are volcanic gases?
Sulphur dioxide and carbon monoxide get released into the atmosphere — can travel long distances due to their potency
41
Name 3 secondary hazards as a result of a volcano
1. Lahars
2. Jokulhlaups
3. Acid rain
42
What are lahars / how do they occur
A combination of rock, mud and water which quickly travel down the sides of volcanoes
Can occur due to meltwater from volcano heat or when an eruption coincides with heavy rainfall
43
What are jokulhlaups?
Snow and ice glacier meltwater after an eruption which causes sudden flooding
44
What is acid rain?
When sulphur dioxide gets released into the atmosphere and mixes with the moisture in the air
45
What is the hazard risk equation?
Risk = hazard x vulnerability
——————————
Capacity to cope
46
What factors make a place at high risk?
- if their capacity to cope is low
- they are quite vulnerable
- the hazard is large / high intensity
47
What is isostatic readjustment / post-glacial adjustment?
Where ice masses / glaciers caused the land mass to sink
The weight of the ice compresses the land
When this ice melts the crust can rise
48
Name the 2 types of volcanic eruptions
1. effusive
2. explosive
49
Describe what an effusive volcanic eruption is like
- Where lava steadily flows out of a volcano onto the ground
- dissolved gases escape easily
- sloping shield volcanoes I.e Hawaii
50
Describe what an explosive volcanic eruption is like
- occurs when cooler, more viscous magma reaches the surface
- dissolved gases cannot escape easily
— causes pressure to build
- gas explosions; rock bombs
51
What are the two shapes of a volcano?
1. composite volcano i.e Mt Fuji
2. shield volcano I.e eyjafjallajokull
52
Why do people live in hazardous volcano zones?
- fertile soils
- minerals
- tourism
- family ties
- cheaper living
53
Define a submarine earthquake
Convergent plate boundary which displaces the water column above (causes tsunamis)
54
What is a locked fault?
Fault which cannot ‘slip’ because the frictional resistance on the fault is greater than the sheer stress along the fault
55
Who came up with the theory of continental drift?
Alfred Wegener
56
Continental crust properties:
Continental
Age
Colour
+ example
Thickness
Density
Continental
Age. >1500 mil years old
Colour light I.e granite
+ example
Thickness 35-40 km on average
Density light: 2.6 mg/m^3
57
Oceanic crust properties:
Oceanic
Age
Colour
+ example
Thickness
Density
Oceanic
Age >200 mil years
Colour Dark I.e basalt
+ example
Thickness 6-10km on average
Density Heavy: 3.0 mg/m^3
58
What is a harmonic tremor and what are they typically followed by?
Continuous rhythmic earthquakes which can be detected by seismographs
- often precede volcanic eruptions
- underground movement of magma
- long duration
59
How did wegener prove his theory, and what discovery in 1948 concluded that the plates were being driven apart
- geological and fossil evidence which connects broken up continents
Rocks of similar age and type found in Africa and South America
1948 mid Atlantic ridge was discovered — suggested processes were driving the plates apart
60
Composite volcano properties:
Composite
Temp
Margin
Silica
Gas
Lava viscosity
Composite volcano properties:
Composite
Temp Cooler: 600-800°
Margin Convergent
Silica High: 70%
Gas High: 4-6%
Lava viscosity Thick
61
Shield volcano properties:
Shield
Temp
Margin
Silica
Gas
Lava viscosity
Shield volcano properties:
Shield
Temp Hotter: 1000-1200°
Margin Divergent
Silica High: 70%
Gas Low: 0.5-2%
Lava viscosity Runny
62
What are the 3 types of lava?
1. Andesitic lava
2. Basaltic lava
3. Rhyolitic lava
63
Define magnitude
Measures amount of energy released at the epicentre
64
What are the 2 types of magma, and some of their proprieties?
1. Basic magma
- rich in iron, aluminium
- low silica content
- low viscosity
2. Acid magma
- rich in silica
- relatively low temp
- high viscosity
65
What is the MMS (moment magnitude scale) and what does it record?
It measures large earthquakes
Records:
- size of seismic wave
- resistance of affected rocks
- amount of slippage
66
What is the Mercalli scale and what does it record? Is it reliable?
It measures large earthquakes
Records:
- intensity of earthquakes
- based on opinion; subjective; unreliable
- uses amount of damage as an indicator of earthquakes intensity
- it doesn’t consider economic, environmental and social impacts
67
What does the VEI (volcanic explosivity index) record?
Records:
- measures relative explosiveness of a volcanic eruption
- based on height of ejected material and duration of eruption
- scale goes from 0-8 and is logarithmic
68
What does the Richter scale record?
amplitude of waves produced during and earthquake
- most widely used scale
- logarithmic scale
- must infer social or environmental impact which can be misleading
69
What does the PAR (pressure and release model) measure?
It’s used to analyse factors which causes a population to be vulnerable to a hazard
It considers the hazard itself and along with the factors that determine the populations vulnerability
- complex
70
What factors increase the resilience of a community?
- positive attitude of people
- pre-planning
- good communications
- wealth of nation
- emergency procedures
- foreign debt repayments
- medical supplies available
71
What factors decrease the resilience of a community?
- low doctor patient ratio
- lack of skills
- unequal trade agreements
- rapid population growth
- environmental degradation
- large scale rural to urban migration
72
What characteristics are on a hazard profile? (Conducted after hazard occurs)
1. frequency of hazard
2. Magnitude — how extensive it could affect
3. Duration — how long it lasts
4. Speed of onset
5. Fatalities
6. Economic loss
7. Spatial predictability — where would be affected
73
What are hazard profiles used for?
Help with decision making when deciding where to allocate most human and financial resources
74
What human and physical factors affect the severity of hazards on populations?
Human:
- wealth
- access to education
- housing
- healthcare
- income opportunities
Physical:
- accessibility
- urbanisation
- population density
75
How does governance / investment influence the scale of a disaster?
- corruption
- building codes and regulations
- preparedness plans
- infrastructure
- emergency services
- communication systems
- public education and practised hazard response
76
What are the issues with using hazard profiles?
- degree of reliability in comparing different events
- easy to compare hazards of same type however difficult to compare across hazards as they have different impacts
- difficult to gather data from remote areas
77
What is a mega disaster?
A high magnitude, high impact, infrequent disaster that affects several countries directly or indirectly
78
Define a multiple hazard zone
A place where multiple hazards occur
79
Describe the pattern of multiple hazard zones around the world
They are predominantly in Asia (including japan, the Philippines, Taiwan, Indonesia) along with Central America (Guatemala, Costa Rica)
80
How can scientists predict when earthquakes happen?
Currently it isn’t possible to predict
Earthquake risk can be forecasted bashed on statistical likelihood
81
What role do scientists play in prediction and forecasting?
The encourage and enforce stricter building regulations by the government
82
How is hazard risk reduced?
- disaster preparedness
- adaption to climate change
- development
- disaster recovery
- disaster response
- disaster mitigation
83
What is the hazard management cycle?
A process in which governments and other organisations work together to protect people from the natural hazards that threaten their communities
AIM: REDUCE LOSS OF LIFE AND PROPERTY
84
What are the stages within the hazard management cycle?
Before the hazard event;
Preparation
HAZARD EVENT;
Response
After hazard event;
Recovery
Mitigation
85
What are they key players within the hazard management cycle?
- governments
- international organisations
- businesses
- community groups
86
How can tsunamis, earthquakes and volcanoes be prepared for?
Tsunamis:
- infrastructure I.e seawalls
- tsunami warning systems i.e DART
earthquakes:
- monitor seismic activity
- hazard profiles
- land-use zoning
Volcanoes:
- hazard maps
- monitor temperatures
- visual signs I.e ice melting, cone changing shape
- lava flows diversions
87
Define mitigation
Ways to prepare in advance in the event of a hazard
88
Define adaption
Strategies designed to reduce the impacts of hazard events i.e education, community preparedness
89
What are some mitigation strategies
- houses on wheels
- mounds / channels
- diversion of lava flows
- land-use zoning
90
What is the parks model?
A graphical representation of human responses to hazards to hazards. It shows out the steps of recovery after a hazard giving a rough indication of timeframe
Steepness of curve:
Shows how quickly an area deteriorates and recovers
Depth of curve:
Shows scale of disaster
91
What are the 3 stages to the parks model? (3 R’s)
Stage one — relief
Hours to days
Stage two — rehabilitation
Days to weeks
Stage three — reconstruction
Weeks to years
92
Name some examples of short term aid
- providing aid, water, food, shelter
- providing financial assistance so people can rebuild their livelihoods
93
Name some examples of long term aid
- rebuilding homes
- building and repairing infrastructure
- reopening schools and businesses
94
What is the role of insurers during disasters?
Insurance coverage can help communities recover from disaster
In many countries few people have insurance as more pressing economic needs take priority
— they are more vulnerable + less resistant
I.e New Zealand had insurance and was rebuilt in 2 years (2011 Christchurch) whereas Haiti 2010 didnt
95
What is the role of NGO’s and TNC’s during disasters?
They provide funds, coordinate rescue efforts and help develop reconstruction plans
Charity events may be hosted to raise money
96
What inequalities may affect a communities resilience to a hazard?
- asset inequality
- political inequality
- social status inequality
- entitlement inequality
97
What are aseismic buildings?
Buildings designed to withstand or minimise destruction during an earthquake
98
What is continental drift?
The movement of tectonic plates, due to varying weights of crust. It was originally thought that convection currents caused the movement of the plates, but now slab pull is thought of as the primary driving force
99
What is Degg’s model?
A model that shows that a hazard becomes a disaster if it affects a vulnerable population
100
What is a love wave?
A surface earthquake wave with horizontal displacement
101
What are primary waves?
An earthquake wave causing compressions within the body of rock
102
What are secondary waves?
An earthquake wave causing vertical displacement within the body of rock
