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Geography > 3.1.5.1: Concept of a hazard + plate tectonics > Flashcards

3.1.5.1: Concept of a hazard + plate tectonics Flashcards

1
Q

Define hazard

A

Something that’s a potential threat to human life or property

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2
Q

Define natural hazard

A

A threat to human life or property caused by a natural process

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3
Q

Give the 3 types of natural hazard

A

Geophysical, atmospheric, hydrological

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4
Q

Define and give examples of a geophysical hazard

A

Hazard caused by land processes e.g. earthquakes, volcanic eruptions, landslides and tsunamis

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5
Q

Define and give examples of a atmospheric hazard

A

Hazard caused by climatic processes e.g. tropical cyclone, storms, drought, extreme hot or cold and wildfires

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6
Q

Define and give examples of a hydrological hazard

A

Hazard caused by water movement e.g. floods or avalanches

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7
Q

Define disaster and its limitations as a definition

A

When a hazard seriously affects humans however it is a political decision to class an event as a disaster so doesn’t have an official definition

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8
Q

Define risk

A

The likelihood humans will be affected by a disaster by establishing the probability a hazard will occur within a given period of time

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9
Q

Define vulnerability

A

How susceptible a population is to the damage caused by a hazard

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10
Q

What are economic determinants of hazard perception ?

A

Richer people often perceivge hazard risk as smaller as they can afford to move to less hazard prone areas and build stronger homes

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11
Q

What are cultural determinants of hazard perception ?

A

People can view hazards as an act of God’s punishment

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12
Q

What are social determinants of hazard perception ?

A

Level of education as people with a better education will be able to prepare better to survive a hazard and know the risks of where they live for better mitigation

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13
Q

What are the 6 characteristic human responses to hazards ?

A

Fatalism, adaptation, mitigation, risk sharing, prediction, management

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14
Q

Explain fatalism

A

Believing hazards can’t be avoided so accepting they will happen- defeatist attitude

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15
Q

Explain prediction

A

Scientific research to deliver warnings and reduce impacts of future events

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16
Q

Explain adaptation

A

Preparing to survive the event by adding features such as earthquake resistant buildings (only effective in HIC developed countries)

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17
Q

Explain mitigation

A

Strategies to minimise the impacts of future events e.g. build houses away from areas previously flooded

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18
Q

Explain management

A

The combination of prediction, adaptation and mitigation to reduce the overall effect of hazards

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19
Q

Explain risk sharing

A

Community preparedness to share a risk e.g. shared cost of insurance and being prepared with medical and food supplies

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20
Q

What are features relating to hazard incidence and the nature of natural hazards ?

A
  • Distribution
  • Magnitude
  • Level of development/ preparation
  • location (rural/urban)
  • Population density (sparse/dense)
  • Intensity
  • CLIMATE CHANGE
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21
Q

Explain the Parks Model

A

Shows how people respond to hazards which can help predictions to mitigate the impacts of future events

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22
Q

Give the 5 stages of the Park model

A
  • Pre-disaster
  • Disruption
  • Relief
  • Rehabilitation
  • Reconstruction (if buildings built to same standard area returns to normal but a higher standard means the vulnerability to hazards decrease)
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23
Q

Evaluate the Park model

A
  • Disaster is broken down into clear sections which helps local governments understand their roles at each stage
  • Model can be easily adapted to different types of natural hazard
  • Visually easy to interpret
  • Focusses on broader community and governmental response instead of smaller vulnerable groups such as low income families
  • Doesn’t fit a diverse context as model doesn’t always account for local cultural, economic, or environmental factors that affect how communities respond to natural hazards
  • Generalised so needs to be manipulated for HICs and LICs
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24
Q

Give the 4 stages of the hazard management cycle

A
  • Mitigation
  • Preparedness
  • Response
  • Recovery
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25
Evaluate the hazard management cycle
- Model can be adapted to various types of hazards and large scale or localised ones - Encourages a constant feedback loop of learning and adaption - Doesn't reflect differences between HIC and LICs experiencing hazards
26
Describe the inner core
- Solid ball containing iron and nickel - Pressure high so iron doesn't melt
27
Describe the outer core
- Semi-molten, iron and nickel - Creates Earth's magnetic field
28
Describe the mantle
- Mostly silicate rocks - Asthenosphere is semi-molten - Largest layer (84% of Earth)
29
What makes up the lithosphere?
Rigid top part of mantle and crust
30
What is the outermost layer of the Earth called?
Crust
31
What is moho discontinuity?
Junction between Earth's crust and mantle where s and p waves are modified
32
Describe features of oceanic crust
- 6-10km thick - Less than 200 million years old (younger due to constant process of sea-floor spreading) - Heavier density - Basalt - Result of erupted mantle material,cooled and modified by seawater salt - 60% Earth's surface
33
Describe features of continental crust
- 30-70km thick - Over 150 million years old - Lighter density - Layers of igneous sedimentary rock - 40% Earth's surface
34
What is the theory of plate tectonics?
The lithosphere is divided into tectonic plates which move in relation to eachother and meet at plate boundaries
35
Explain early tectonic theories
- Wegener believed in Pangea where all continents were one big land mass in a C shape that spread across the equator 250 million years ago but moved apart due to continental drift - Pangea was split into 2 large continents Laurasia and Gondwanaland
36
Give 3 pieces of evidence to how we know continents have moved
- Similar fossils found on different continents - Similar patterns of rock layers found in different continents - Shape of continents fit together
37
Explain gravitational sliding
Another name for ridge push
38
Explain the theory of ridge push
- At constructive margins magma rises to surface and forms new crust which heats surrounding rock which expands and rises above surface forming a slope - New crust cools and becomes denser causing the rock to move downslope (gravitational sliding) - Puts pressure on tectonic plates causing them to move apart
39
Explain the theory of slab pull
- At destructive plate margins when the denser crust subducts under the less dense crust due to the cooling of the oceanic plate over time and metamorphism (pressure as the plates collide) increases the density of the plate leading to subduction. - Stress is transferred back up through the brittle lithosphere to the plate at the surface during sibduction pulling it along by slab pull
40
Explain the theory of convection currents
- Less accepted theory and more focussed on sinking of colder and denser PLATES - Lower parts of asthenosphere heat up, become less dense and slowly rise as Earth's mantle is hotter closest to core - As they moveg towards the rop they cool down, become more dense and slowly sink - Circular movements of semi-molten rock create drag on the base of tectonic plates causing them to move
41
How does a ridge form?
Tension forces cause plate thinning so hot mantle rock flows up to fill space which creates positive buoyancy and uplifts the ridge
42
How does magma form?
As mantle rock rises it experiences a reduction in pressure causing partial melting forming magma
43
How does movement in the asthenosphere contribute to movement of plate tectonics?
As slab descends into the mantle it displaces mantle rock creating currents which help pull the plates towards the trench through SLAB SUCTION
44
Explain seafloor spreading
- As tectonic plates diverge magma rises u[, cools and forms new crust - Over time the new crust is dragged apart so more crust forms between it through slab pull and ridge push moving plates - Sea floor gets wider - Creates mid-ocean ridges
45
What % of plate movement is ridge push ?
10
46
What % of plate movement is slab pull ?
90
47
Give a piece of evidence for the occurence of sea-floor spreading
- Paleomagnetism (when lava solidifies the particles provide permanent record for Earth's polarity at time of eruption) and Earth's polarity reverses at regular intervals resulting in series of magnetic stripes -
48
Define constructive boundary and what can it also be referred to as ?
(Divergent boundary) where plates pull away from eachother
49
What hazards occur at a constructive margin ?
- Earthquakes - Volcanoes
50
What landforms form at a constructive margin ?
- Ocean ridge - Rift valleys
51
How do volcanoes form at constructive margins ?
Mantle is under pressure from moving plates above, the release of pressure causes the mantle to melt forming magma which is less dense than plate above so rises and can erupt to form a volcano
52
How do earthquakes occur at constructive margins ?
Plates don't move in a uniform way causing pressure to build until the plates crack forming a fault line which releases seismic energy in the form of an earthquake
53
How do mid ocean ridges form ?
Seafloor spreading creates an underwater mountain system with a valley called a rift running through the spine e.g. Mid-Atlantic-ridge (Eurasian and North American plate)
54
How do rift valleys form ?
The divergence of plates beneath land stretches the lithosphere causing it to fracture into parallel faults of upright blocks called horsts. Crust beneath the fault drops down forming the valley. e.g. East African Rift valley + volcanoes found here e.g. Mount Kenya
55
Define destructive boundary and what can it also be referred to as ?
(convergent) Where 2 plates are moving towards eachother
56
What forms at an oceanic-continental destructive plate margin ?
- Deep sea trench - Fold mountains - Volcanoes - Earthquakes
57
How do volcanoes form at oceanic-continental destructive plate margins?
- Magma (formed from melting of plate in the BENIOFF ZONE) is less dense than continental crust above so rises to surface forming composite volcanoes
58
How do earthquakes form at destructive plate margins?
Plates get stuck as they move under eachother causing a pressure build up until they jerk past eachother releasing seismic energy in the form of earthquakes
59
How do deep sea trenches form destructive plate margins?
Formed when the more dense oceanic crust is forced under the less dense continental e.g. Marianas Trench in Pacific ocean
60
How do fold mountains form at oceanic-continental destructive plate margins?
Sediment accumulated on the continental crust is folded upwards along with the edge of the crust when the plates meet
61
Describe features of composite volcanoes
- Destructive plate margins - Erupt infrequently due to viscosity of andesitic magma (due to high silica content) - Tall steep sided - e.g. Mount Fugi
62
Describe features of shield volcanoes
- Runny basaltic lava - Gently sloping - Occur at rift valleys - e.g. Hawaii
63
Define seismicity
Frequency and distribution of earthquakes in an area
64
Define volcanicity
Process of molten rock and gasses extruding onto Earth's surface or intruding into Earth's crust
65
What is the VEI
Volcanic Explosivity Index
66
What forms at an oceanic-oceanic destructive plate margin ?
- Deep sea trench - Island arcs - Volcanoes - Earthquakes
67
What is the link between volcanoes and island arcs at oceanic-oceanic destructive plate margins?
Volcanic eruptions from SUBMARINE VOLCANOES take place underwater to create island arcs which are clusters of islands that sit in a curved line e.g. The Mariana Islands
68
What forms at a continental-continental destructive plate margin ?
- Earthquakes - Fold mountains Both plates same density so no subduction only COLLISION ZONE CREATED
69
How do fold mountains form at a continental-continental destructive plate margin?
- Plates move towards eachother and over millions of years the continental rock is eroded and weathered - Sediment builds up in flat layers under sea - Pressure causes rocks such as sandstone to form - At collision zone sedimentary rock crumples into folds e.g. Himalayas
70
Explain the formation of thrust faulted mountains
Tectonic plates collide triggering deformation and thickening of crust leading to uplift and mountain formation. Horizontal compression causes faulting of layers into folds
71
What only occurs at a conservative plate margin and why?
Earthquakes as the two plates moving past eachother get locked together causing a pressure build up causing them to jerk past eachother or crack to form fault lines which releases seismic energy as earthquakes - e.g. many earthquakes along San Andreas Fault in California
72
How old is a young fold mountain ?
Less than 25 million years old
73
What is a magma plume ?
A vertical column of hot magma that rises up from mantle where volcanoes form above it
74
How do magma plumes relate to plate movement?
Magma plume remains stationary over time but crust above it moves meaning volcanic activity in part of crust above magma plume (HOT SPOT) decreases until new volcano forms above it forming a chain of volcanoes e.g. Hawaii was formed by magma plume

Geography (29 decks)

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