Hazards 🌋 Flashcards
What is a hazard?
A natural event with potential to cause harm to life or property
becomes disaster when buses significant impacts to people
3 types of hazard
Geophysical (caused by land processes) earthquakes, volcanoes, tsunami
Atmospheric (caused by climate) tropics, storms, droughts
Hydrological (caused by water) floods
Risk definition
Likelihood humans will be affected by hazard
Vulnerability definition
How susceptible the population is to damage caused by hazard
what is hazard perception?
the way people view and processes hazards
determines how they respond
Factors that affect people’s perception of hazards
Wealth (richer perceive as smaller, can move away or prepare)
Religion (act of god)
Education (better understanding)
Past experience
Personality (fear)
responses to hazards (based on perception)
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
Outline the park model
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
Use of park model
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
Outline hazard management cycle
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
Comparison of park model and HMC
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
Structure of the earth
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
Why is the core hot?
Radiogenic heat - due to radioactive decay of elements
Primordial heat - heat left over from earths formation
Heat drives tectonic activity
Ways techtonic plates move (theories of movement)
Convection currents
Slab pull
Ridge push
What are convection currents?
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
What is slab pull?
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
What is ridge push?
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
What is sea floor spreading?
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
What is plate tectonic theory?
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
Evidence for plate tectonic theory
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
destructive subduction
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
destructive collision
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
constructive
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
conservative
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
