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Geography - The challenge of natural hazards (Earthquakes (Secondary…
Geography - The challenge of natural hazards
Natural Hazards
A natural event
that poses the risk of being dangerous or disastrous to
humans, properties, societies and the environment
.
No risk :arrow_right: Just a natural event
Geophysical hazards
[Earth Physical]
Caused by physical processes on, above or within the Earth such as the movement of tectonic plates
Hydro-meteorological hazards
[Water Weather]
Caused by changes in the weather and/or water.
Droughts, Floods, Cyclones
Disaster is when loss of life happens
Risk is the chance of a hazard occuring
Vulnerability is the conditions caused by physical, social, economic and environmental factors which increases impact of hazards
Volcanoes
Shield
At Constructive boundaries
Gentle slopes, wide base
Lava is balsatic (runny) so it spreads wider and gains little height after several eruptions.
Gentle slopes, low wide cone
Layers of runny lava with little ash
Frequent but not violent eruptions
Mauna Loa
Composite
At Subductive boundaries
Steep sides, narrow base
Lava is viscous so it does not flow outwards so it builds higher after several eruptions. These are layers of granite and pyroclastic flow. Secondary vents caused by blockage in main vent.
Steep sided, and cone-shaped
Layers of ash and lava
Infrequent but violent eruptions
Mount Vesuvius
Primary effects are direct effects of the eruption
Lava flows
Pyroclastic flows
Eruption cloud
Secondary effects are indirect effects of the eruption
Homelessness
Lahars
Blocked roads
Water shortages
Suffocation (due to carbon dioxide released)
Tsunamis (from lots of debris crashing into water, and underwater volcanoes displace a lot of water from tremors)
Monitor/Prediction
GPS Satellites and tiltometers - measuring changes in ground deformation which may indicate manga build up (May be limited to HICs)
Thermal heat sensors detect changes in volcano surface temp (May be limited to HICs)
Protection
Evacuation
Preparation/Planning
Evacuation plans/strategies
Emergency shelters with food supplies
Tectonics
Types of plate boundaries
Destructive
Denser oceanic plate
subducted
beneath continental
(Composite) Volcanoes - The oceanic plate melts, forming magma which rises, creating pressure till it erupts through cracks in the crust.
Violent earthquakes as the two plates rub against each other
Deep-ocean trenches caused by the denser ocean plate is subducted
Fold mountains can be caused in the continental plate by the collision
Conservative
(Any) Two plates moving side by side, in the same or different directions, no land is created or destroyed
Earthquakes - Friction build-up between plates is suddenly released as kinetic energy which creates seismic waves.
Especially at conservative boundaries there is a shallow focus
Constructive
(Any) Two plates
move apart
from each other, where magma rises up to form new crust.
(Shield) Volcanoes are formed as the magma rises through cracks in the crust
Mid Ocean Ridges - These can be caused from magma rising to fill the cracks and cooling
Collision
(Any two same)Two plates of equal density are pushed together, and since they are the same density, neither subducts
Fold Mountains - Geosynclines holding sediment are compressed pushing the sediment upwards
e.g. Indian plate and Eurasian plate - Himalayas
Scales
VEI stands for Volcantic Explosivity Index. It is used to measure destruction through amount of debris erupted.
Mercalli Scale
Qualitative
I to XII
Measures intensity and effects, based on subjective descriptions
Richter scale
Quantitative
Measures strength/magnitude
Logarithmic
Up to 10
Earthquakes
An earthquake is the shaking of the surface of the earth, resulting from the sudden release of energy in the Earth's lithosphere that creates seismic waves.
They are most prominent at conservative and destructive plate boundaries
Focus - the origin of the seismic waves in the crust. The deeper the focus, the less severe
Epicentre - The first point on the crust where seismic waves can be felt
Formation
Destructive
Two plates moving together
Subduction
Friction
Suddenly overcome
Earthquake
Conservative
Sliding past
Friction
Sudden jolt
Earthquake
Primary effects are direct effects of the earthquake
Secondary effects are indirect effects of the earthquake
Tsunamis
Offshore epicenter displaces water because the seabed moves
Tsunamis form at the coast because of shallow seabed creating friction, slowing it down.
Shoaling waters - Waves more intense and frequent because seabed gets shallower nearer to coast
Landslides
Mudslides
Avalanches
CASE STUDY : CHILE 2010 vs NEPAL 2015
(how levels of development affect impact of tectonic hazard)
Chile
What Type : Destructive Plate Margin
Which Plates :Nazca plate subducted beneath South American
When : 2010 (Feb 27)
Magnitude
8.8 (Richter Scale)
Just off coast of central Chile
Effects
Primary
500 killed
12,000 injured
Over 200,000 houses destroyed
4,500 schools destroyed
Santiago airport badly damaged, hampering international aid efforts
$30 bn overall
Secondary
1500km of roads destroyed by landslides - cutting off remote communities
Coastal towns and Pacific countries affected by tsunami (It happened just off the coast)
Responses
Short term
Emergency services and international help supplied field hospitals
Temporary repairs to route 5 highway within 24 hours, enabling transport of aid from Santiago to remote communities
Power and water restored to 90% of homes in 10 days
National appeal raised $60mn
Long term
Housing reconstruction planned to help nearly 200,000 a month after
Strong economy based on copper exports, didn't require much foreign aid
President announced it could take as little as 4 years to fully recover
GDP : 38th out of 193 countries
HDI : 41st out of 187 countries
Chile has a higher HDI and GDP than Nepal, it is a lot more developed
Nepal
Which Plates : Indo-Australian and Eurasian plates
When : 2015 (Apr 25)
What Type : Destructive Plate Margin
Magnitude
7.9 (Richter Scale)
80km North - West of Capital (Kathmandu)
Responses
Short term
UK + India + China sent rescues teams and water/medical supplies promptly
Helicopters delivered supplies to villages that had been cut off by landslides
300,000 people migrated to Kathmandu for shelter / support
Long term
Roads repaired
Landslides cleared
Heritage sites re-opened to boost tourism
Effects
Primary
9,000 killed
20,000 injured
3 million homeless
7,000 schools destroyed
$5bn overall cost
1.4 million without food, water or shelter for days - weeks after
Secondary
Roads blocked by landslides, hampering relief efforts
Avalanche left 250 missing
Avalanche on Everest killed 19
GDP : 109th out of 193 countries
HDI : 145th out of 187 countries
Monitor / Prediction
Sensitive seisometers for measuring foreshocks (May be limited to HICs)
Locations and times can be used to predict future earthquakes
Protection
Earthquake-proof buildings (May be limited to HICs)
Rolling weights on top of roof to counteract shock waves
Birdcage interlocking steel frame
Strenghthened roads and buildings and bridges (May be limited to HICs)
Preparation/Planning
Earthquake Drills (Japan every 1st September)
Residents learn to turn off main gas, electricity and water supplies to prevent leaks
Geography - Climate Change
Climate change
Causes
Urbanisation
High rise buildings prevent heat from transferring to higher atmosphere
Known as urban heat island (UHI)
Slower cooling rates as buildings slow wind speeds, less cooling via convection
Decreases albedo
Ice melting decreases albedo, allowing more sunlight to be absorbed
Deforestation
Burning of fossil fuels
Green house effect - More heat trapped in the troposphere where greenhouse gases re-emit heat that usually would be radiated away
Impacts / Evidence
Increased frequency of hydro meteorological as oceans are warmer
Poles shrink due to melting in Summer, up to 40% more than they naturally would - they may disappear by 2040
Oceans warming and sea levels rising
In 17 years, 1000 years worth increase of CO2 levels
CO2 levels increased to record high of 386 units (in a million)
Before industrial revolution the highest had been 290 units
Last 200 years increase of 1 C
Responses
Mitigation
Alternative energy sources that emit less CO2
CCS (Carbon Capture and Storage)
Planting trees to reduce CO2 level
'Carbon sinks'
Moisture released has cooling effect as clouds block solar radiation
Adaptation
Agriculture
Drought - resistant strains
New irrigation systems
Artificial glaciers can provide water
Rising sea levels
Artificial islands made 3m higher
Houses raised on stilts
Extreme weather in the UK
Causes
Island - weather influenced by continent and ocean
High pressure over Northern Europe can block air mass and weather systems coming from East
Jet stream can get 'stuck' - prolonged periods of extreme weather
More energy in atmosphere - increases severity of storms
2009 Heavy Snow
20 cm in capital
2015/16 Floods
December 2015 was wettest and warmest month EVER recorded in the UK
2003 Heatwave
Railway tracks buckled
Roads melted
x>2,000 died in Europe
38.5 C in Kent
'Roundabout location'
When jet stream travels North, it blocks off the clod air masses (polar maritime and polar continental)
When jet stream travels South, it blocks off the warm air masses (tropical maritime and tropical continental)
Meeting point of 4 different air masses (+ 1 less important one) each bringing different condition during the year
Geography - Weather hazards
Tropical storms
Formation
Air draws water vapour from ocean surface
It cools as it rises, condensing to form towering thunderstorm clouds
As it rises, it leaves an area of low pressure beneath it, which draws in more air from the surroundings
Heat is released which powers the storm, drawing up more water from the ocean
Several smaller storms join to form a giant spinning storm
Eye at center is where air descends rapidly, eyewall is where most intense weather conditions are felt
Where they occur and why
Warm oceans (>27 C)
5-15 degrees from equator as at equator there isn't enough spin for Coriolis effect to take place
Intense heat in tropical regions make air unstable and rise quickly
Summer / Autumn when sea temperatures are highest
Effects
Primary
Buildings destroyed or damaged
Power lines destroyed
Electrical supplies cut off
Sewage released
Water supplies become contaminated
Secondary
People left homeless
Water borne diseases more prevalent as lack of clean water / sanitation
Road and rail networks blocked by debris
Responses
Immediate
Food aid / supplies
Monetary / Financial aid from other countries
Search and rescue teams
Long-term
Monitoring / Prediction
Satellite / radar technology to track development and approach
Weather charts and computer software to predict path
HIC such as US have effective hurricane monitoring and prediction system
Able to issue warnings to alert people and give time for preparation
LIC are often less prepared
Monitoring equipment is expensive and hard to communicate information to those in remote locations (most likely to be affected often)
Preparation / Planning
Stocking up on food and water
Early warning systems
Being educated and what to do in event (evacuation orders and routes)
Relation to climate change
Causes
More heat
More water in atmosphere
Warmer sea surface temperatures
Effects
Higher intensity storms
More frequently / likely to occur
Wider distribution
Protection
Windows covered with metal shutters
Storm shelters
Buildings with deep concrete pillars to dissipate energy
Case Study : Hurricane Katrina
Category 5
Storm surges over 6m high
New Orleans affected the worst (80% flooded)
Environmental
Dead Crops: Many crops were destroyed and meant that there
wasn't enough food
to provide for the entire community
Flooding : New Orleans and other states were
left below sea level
, as their levees broke due to the severity of Hurricane Katrina - causing flooding.
Economic
Damage : Around
$300 billion worth of damage
was caused. Many houses and business were destroyed.
Insurance - Approximately
$40 billion
were spent just on insurance, as people had applied for car, house, pet, health insurance and the government had to pay for new jobs, homes etc.
Looting : Criminal gangs roamed the streets
looting homes and stealing valuables
from other places.
Social
Deaths :
Over 1500 people
lost their lives
Homelessness :
800,000 housing units
destroyed
Millions of people were forced to take refuge in the Super bowl
This lead to extreme conditions - diseases and illnesses
More money spent on medication and doctors
Water : Drinking water system was contaminated so disease spread easily
(Cholera, diarrhea)
Responses
Short term
National Guard mobilised to restore and maintain law and order
$50bn in aid from government
UK government sent food aid
Long term
Roughly 200 miles of flood walls and levees strengthened or replaced
Roughly $17bn for rebuilding damaged houses and infrastructure
Emergency aid services have been made more efficient
