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Physical Geography 🌋 > Hazards 🌋 > Flashcards

Hazards 🌋 Flashcards

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1
Q

What is a hazard?

A

A natural event with potential to cause harm to life or property

becomes disaster when buses significant impacts to people

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2
Q

3 types of hazard

A

Geophysical (caused by land processes) earthquakes, volcanoes, tsunami
Atmospheric (caused by climate) tropics, storms, droughts
Hydrological (caused by water) floods

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3
Q

Risk definition

A

Likelihood humans will be affected by hazard

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4
Q

Vulnerability definition

A

How susceptible the population is to damage caused by hazard

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5
Q

what is hazard perception?

A

the way people view and processes hazards
determines how they respond

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6
Q

Factors that affect people’s perception of hazards

A

Wealth (richer perceive as smaller, can move away or prepare)
Religion (act of god)
Education (better understanding)
Past experience
Personality (fear)

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7
Q

responses to hazards (based on perception)

A

Fatalism - accept they are part of life, may be religious reasons, loses are inevitable
fear - people move away

active:

mitigation - actions aimed at reducing severity of event and therefore impacts
Through:
Adaptation - changing behaviour accordingly to reduce impacts
prediction - advancements in technology, can give warnings and evacuate

risk sharing - sharing the costs of reducing the hazard and the benefits of preventing it
eg insurance (richer) all buy but only some use

Management - governments may coordinate responses to manage them effectively

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8
Q

Outline the park model

A

Pre disaster - before event, QoL normal
Disaster - during and directly after, destruction, deaths, reduced QoL
Relief - short term aftermath, focus on saving people and preventing further damage
Rehabilitation- temporary shelter and aid for people
Reconstruction - rebuilding houses and infrastructure
(QoL either returns to same standard or can improve)

Identifies stages of recovery
Assists in planning for future hazards and therefore improve outcomes by reducing impacts

Steeper drop shows larger magnitude of event
Steepness of upwards curve depends on - planning, development and aid

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9
Q

Use of park model

A

Identifies stages of recovery
Assists in planning for future hazards and therefore improve outcomes by reducing impacts

Steeper drop shows larger magnitude of event
Steepness of upwards curve depends on - planning, development and aid

+ shows rate of recovery
+ shows how QoL affected after hazard
- doesn’t show preparedness before
- doesn’t show quantitative data

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10
Q

Outline hazard management cycle

A

Continuous loop explains an approach to managing hazards
Preparedness- using evidence and data from previous events to plan, key to minimising impacts
Response - deploying services and resources to rescue people eg emergency services
Recovery - post disaster reconstruction
Mitigation - action taken to reduce impacts of future hazards eg life safe buildings

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11
Q

Comparison of park model and HMC

A

Both show response of community based on a natural disaster

PM shows impacts of event
- steepness depends of magnitude and response (aid, development and preparation)
HMC more concerned with management before and after - show little of its impact

HMC is a cycle, shows that hazards are ongoing
Unlike future

PM tracks stages of community after (QoL) - help to plan future responses
HMC doesn’t

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12
Q

Structure of the earth

A

Centre - core - iron and nickel
- inner core, solid ball
- outer core, semi molten

Mantle -
lower mantle - hotter and denser then upper
upper mantle
- rigid upper layer (+ crust is lithosphere)
- asthenosphere - plastic, carries lithosphere

Crust
- continental - thicker, less dense, mainly granite
- oceanic - thinner, more dense, mainly basalt

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13
Q

Why is the core hot?

A

Radiogenic heat - due to radioactive decay of elements
Primordial heat - heat left over from earths formation

Heat drives tectonic activity

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14
Q

Ways techtonic plates move (theories of movement)

A

Convection currents
Slab pull
Ridge push

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15
Q

What are convection currents?

A

Heat from core heats magma in mantle
Magma becomes less dense and rises
Spreads in asthenosphere
Cools
Become more dense and sinks

Creates circular movements which create drag underneath the plates

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16
Q

What is slab pull?

A

At destructive subduction plate margins
Denser crust forced under less dense
Plate edge sinks and gravity pulls rest of plate with it towards boundary

landforms associated: volcanoes, island arcs

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17
Q

What is ridge push?

A

Constructive plate margins (mid ocean ridges)
Magma rises to surface, creates new crust
new rocks solidifies and cools, becomes denser and thicker
Causes lithosphere to slope away from ridge
gravity pulls lithosphere down slope
known as gravitational sliding - contributes to movement of plates apart

landforms associated: mid ocean ridges, rift valleys (c)
sea floor spreading

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18
Q

What is sea floor spreading?

A

Happens when plates move apart (constructive)
Magma rises to form new crust
Pulled apart and new crust rises

Causes sea floor to get wider
Cause formation of mid ocean ridges (higher area either side of margin)

evidence from paleomagnetism
- when earths polarity reverses
- magnetite lines up with magnetic field, reverses
= alternating bands as crust forms overtime

19
Q

What is plate tectonic theory?

A

Lithosphere broken up into plates
Move due to convection currents in asthenosphere
Caused by less dense magma rising, cooling and sinking

move by:
convection currents, slab pull, ridge push, sea floor spreading

can help with knowing which areas are at risk along margins
- but not all hazards occur here

20
Q

Evidence for plate tectonic theory

A

Continental fit
- continents fit together

Geological evidence
- rocks of same type and age found across
continents (used to connect)

Climatological evidence
- some continents contain coal deposits
formed in tropical conditions, must have
drifted (eg UK)

Biological evidence
- similar fossils found across continents (eg mesosaurus)

palaeomagnetism
- earths polarity reverses every 40,000 years
- magnetite (magnetised rock) is created as plates move
- polarity of magnetite changes with poles, showing bands of reversed

21
Q

destructive subduction

A

plates move together - of different densities

  • denser plate (oceanic) subjects below less dense plate (continental)
  • subducted plate melts, due to heat and friction
    molten material rises = volcanoes

C-O
composite volcanoes
earthquakes
fold mountains
trenches

O-O
oceanic trenches
island arc

22
Q

destructive collision

A

plates move together - 2 continental

plates equal densities so neither subducts, force each other up

C-C
fold mountains
earthquakes

no volcanoes as no subduction

23
Q

constructive

A

plates moving apart

new crust continuously created - lava rises to fill gap

mantle under pressure from plates, release when move apart
melts mantle so magma rises = volcano

pressure builds up when plates don’t move at same speed - earthquake when released

O-O
ocean ridges
underwater shield volcanoes

C-C
composite volcanoes
rift valleys

earthquakes at all
- transform faults at right angles to margin - create shallow focus

24
Q

conservative

A

plates move past each other in different directions or same direction at different speeds

no volcanic activity - no subduction

friction causes plates to lock together causing build up of pressure
earthquakes when released

25
Q

magma plumes

A

forms volcanoes away from plate margins
- vertical column of extra hot magma
- creates volcano when magma breaks through surface
- crust moves but magma stays still, creates chain of volcanoes

26
Q

constructive margin landforms

A

earthquakes (all)
ocean ridge (O-O)
rift valley (C-C)
volcanoes (all)

27
Q

destructive margins landforms

A

subduction
(O-C)
volcanoes
earthquakes
fold mountains
trenches

(O-O)
oceanic trenches
island arcs

collision (C-C)
earthquakes
fold mountains

28
Q

what is adaptation?

A

accepting natural hazards are inevitable and changing behaviour accordingly

29
Q

what is mitigation?

A

actions taken to reduce the severity of the event and therefore impacts

can be before or after the event

30
Q

what is preparedness?

A

how ready an area is to deal with the hazard, aims to reduce the impacts

31
Q

what is prevention?

A

actions aimed at preventing large scale events occurring

32
Q

Why are poorer areas more vulnerable to hazards?

A

Fewer warning systems - lack technology
Fewer defences
Weaker infrastructure
Fewer emergency services
Slower responses

33
Q

formation of an island arc

A

plates move together (destructive)
O-O

denser plate subducts beneath less dense
rising magma from melting crust creating volcanoes
form along plate boundary = cresent of submarine volcanoes
rise above sea level = islands

eg Japan

34
Q

formation of a rift valley

A

plates move apart (constructive) under land

lithosphere stretches, fractures into parallel faults

land between faults collapses into deep valleys - separated by blocks of land

35
Q

formation of fold mountains

A

plates moving together (destructive)
O-C or C-C
created by deformation of the lithosphere

C-C pushed together, no subduction so ride up into each other

O-C subduction but plate still folds

eg The Andes

36
Q

formation of mid ocean ridges

A

plates move apart (constructive) under water (O-O)

creates mountains
- magma rises up, accumulates over time

creates underwater volcanoes
- magma rises through gap

causes earthquakes
- at transform faults (due to plates spreading at different speeds)

eg Mid Atlantic Ridge

37
Q

formation of deep sea trench

A

plates move towards (destructive)
O-O or O-C

denser oceanic plate subducts under less dense
= trench

outer slope shallower as oceanic plate bends into trench
inner slope steeper

eg Peru-Chile trench

38
Q

formation of island chains

A

occur at magma plumes

hot spot remains the same, but plate moves due to convection currents

= volcanoes in lines along plate
overtime eroded below sea level

new ones created next to extinct one (old volcano moved away from hot spot, not active)

39
Q

formation of a volcano

A

where magma escapes to the surface

constructive - moving apart
- magma allowed to rise

destructive subduction - moving together
- denser plate subducts, friction and heat cause it to melt
- rises to crust

40
Q

nature of volcanoes at constructive margins (and plumes)

A
  • basaltic lava
  • low viscosity, lower levels of silica

creates gentle sloping, wide base volcanoes
- as lava can flow further
- shield

  • high frequency eruptions
  • low magnitude

hazards: lava flow, mud flows

eg Eyjafjallajokull

41
Q

nature of volcanoes at destructive margins

A
  • andesitic lava
  • high viscosity, higher levels of silica

creates steep sides, tall
- as lava can’t flow far, solidifies fast, builds up

  • low frequency eruptions
  • higher magnitude, explosive (vicious lava can block vents, more pressure)

hazards: pyroclastic flow, tephra

eg Mount Pinatubo

42
Q

Factors that create landforms at margins

A

Plate tectonic theory:

convection currents

Gravitational sliding
- Slab pull
- ridge push

Magma plumes (not at margins)

43
Q

Compare volcanic impacts with seismic

A

Seismic generally more destructive
- unpredictable
- violent shaking and infrastructure collapse, especially if epicentre in urban area (9000 deaths in Nepal)
- tsunamis

Volcanic generally more widespread
- ash clouds disrupt travel and agriculture (Iceland)
- Lahars, widespread (Nevada del Ruiz)
- more predictable than earthquakes, can prepare and evacuate (Iceland, 30mins)

44
Q

factors affecting impacts of hazards

A

physical
- magnitude
- duration or frequency

human
- population density
- level of development
- proximity

Physical Geography 🌋 (21 decks)

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