World at risk Flashcards
Geography International Edexel
What is a Hazard
A hazard is a potention threat to humans life and property
What are the diffrent types of Hazards?
Hydro-meterological hazard (climate processes)
geophysical hazard (land processes)
Conext Hazard (effect entire planet)
What forces effect plate tectonics?
- Convection current in the mantle
- Ridge push
- Slab push
What is Ridge push?
It is the gravitational force at the spreding ridges)
What is slab push?
It is the gravitational force in subducting zones)
What is the convection current theory?
- Radioactive decay in the core creates heat
- This heat drives vast convection currents, causing mantle to rise and fall
- This convection moves the plates
Destructive Plate Boundary
Continental-Oceanic
- Denser oceanic plate subducts below the continental plate
- Plate subducting leaves a deep ocean trench
- Oceanic plate is melted as it subducts into the asthenosphere
4.Extra maga forces through weak areas
5.Explosive volcanoes erupt through continental plate known as composite volcanoes - fold montains occur when sedement is pushed upwards during subduction
Destructive Plate Boundary
Oceanic-Oceanic
1.Older more dense plate subducts
2. Leaves a ocean trench
3. Fold mountains may occure
4. Built up pressure causes underwater volcanoes bursting through oceanic plate
5. Lava cools and creates new island arcs
Collision Plate Boundary
- Both plates are the same density so does not subduct
- Pile up of crust on top of litmosphere due to pressure between plates
- Fold mountains
Constructuve plate boundary
Oceanic-Oceanic
- tectonic plates are pulled apart by opposite dirrections of convection currents
- Magma rises in between the gaps left by the two plates seperating, forming new land when it cools
- Less explosive underwater volcanoes formed as magma rises
- New land forming on the ocean floor by lava filling the gaps
Constructive Plate Boundary
Continental-Continental
- tectonic plates are pulled apart by opposite dirrections of convection currents
- Volcanoes form where the magma roses
Conservative Plate Boundary
- Parallel plates move in different directions at diffrent speeds
- No land is created or destroyed
- Can cause fault lines on continental crust
- Plates can become stuck and cause high magnitude earthquakes
5.Can cause a lot of water to be displaced on oceanic crust causing volcanoes
What is an earthquake?
A sudden shaking of the ground as a result of movement within the earths crust or volcanic action
How does tectonic movement cause Earthquakes?
- Plates become stuck due to friction
- Convection currents in the asthenosphere continue to push, which builds pressure
- it builds up and eventually gives way
- The sudden release of pressre causes joilting motions in the plates
- The jolt is responsible for the seismic movement spreading throughout the gorund in the form of seismic waves
What is the focus/hypocentre?
It is the undergorund point where the earthquake originates from
What is the epicentre
It is the area above the ground that is directly above the focus
What secondary hazards do earthquakes cause?
Landslides
Tsunamis
Primary Hazards of Volcanoes
Lava flow-dirrectly from the volcanoe
Tephra and ask flow-Damage to buildings, which can collapes under weight
Volcanic gases-Sulphur dioxide and CO2
Secondary Hazards of Volcanoes
Lahars- Rock, mud and water travel quickly down the sides of volcanoes
Jokulhlaup- Snow and ice in glaciers melt causing sudden floods
Acid rain- Caused by sulphure dioxide
How is a Tsunami formed?
- Oceanic crust is jolted during an earthquake
- Water is displaced above
- water is pulled back down due to gravity
- energy is transfered into the water and travels though it like waves
- The water travels fast but with a low amplitude/ height
- As it gets closer to te coast the sea level decreases so there is friction between the sea bed and the waves
- This causes waves to slow down and again height
(average height=10 feet, but can reach 100 feet)
Usually formed in the subduction zone at convergent plate boundaries
How do landslides happen?
- Earthwuakes can weacken or damage the stucture of material
- Unconsolidated material or loose rocks can collapse
Landslides can travel several miles and accumulate material on the way
Short term hydro-meteological hazards
- Cyclones
- Floods
- Hurricanes
How are Hurricanes formed?
- sea surface tempreture is 26.50c >
- Air is heated above the surface and rises rapidly under low pressure conditions
3.The rising air draws large volumes of moisture from the ocean causing strong winds - The coriolis effect casuses the air to spin upwards around a calm central eye of the storm
- Air rises and then cools and condences to form cumulonimus clouds, which generate rainfall
- Cool air sinks into the eye. therefore there is no clouds and is calmer
- The tropical storm travels across the ocean by prevailing wind
- When it mets land, it is no longer fuelled by the source of the moisture and heat from the ocean, so it looses power and weackens
How can flooding happen?
- Low pressure weather systems (tropical cyclones, depresions) these can displace large volumes of water
- Large volume of rainfall over a prolonged period of time will cause the ground to because saturated, meaning further rainfall is more likely to flow as surface run off into rivers increasing discharge
- Snowmelt, increase temperature will cause snow to melt
What factors affect flooding?
- Impermeable rocks
- Relief, can reduce time taken for water to travel to the river channel. High steep slopes=More runoff
- Intense storm precipitation or rapid snowmelt
- Low density vegetation, therefore less interception and less plant uptake
- Human activity, urbanisation and deforestation
What is a drought
An extended period of deficient rainfall relative to the statistical average for the region
Impacts of drought
-Loss of soil moisture
-Reduction in water available for consumption
-Discharge reduction in rivers
-Threats to wetlands and habitats
-Food storage decrease
-Rural economic collapse
What is the ENSO Cycle
El Nino southern oscillation- Naturally occuring phenomena that involve the movement of warm water in the equatorial pacific
Stages of the ENSO Cycle
El Nino
La Nino
What happens in El Nino
1.Normal conditions- Winds push warm water westward in the pacific ocean, allowing cool water to rise along the South America Coast
2. The Trade winds start to weaken, allowing warm water to move eastward towards South America
3.The warm water accumulates in the central and eastern pacific forming a pool of armer-than-average sea surface temperature
4. The water water in the central and easten pacific ocean lead to changes in atmosphere, incuding rising air increased rainfall in the eastern Pacific and drought conditions in the western pacific
5. Typically lasts for 9-12 months
Stages of La Nino
- trade winds stregthen, causing more upwelling of cold water along the western coast of South America
- Stengthening trade winds lead to a cooling sea surface tempreture in the central and easten Pacific Ocean
- Leads to change in weather patterns. increase rainfall in the westen Pacific and drier conditions in the central and easten Pacific
- Lasts for around 9-12 months
Effects of La Nino
Australia
- Increased rainfall
- Flooding
- Landslide
South America
- Drier climate
- Droughts
Effect of El Nino
Australia
- Droughts
- Heat Waves
South America
- Increase Rainfall
- Flooding
- Landslides
How are Volcanoes Measured?
Volcanic Explosivity Index (VEI) - measured of height of ejected material, duration and Relative explosivity.
How are Earthquakes Measured?
Moment Magnitude
- Measures the amount of energy released in an earthquake
- Scale 0-9
simple so social impacts are not included and need to be inferred
How are hurricanes/ cyclones measured?
Saffir-Simpson
- Measures the severity of a tropical cyclone
- Scale 1-5, where 1 is a weak hurricane and 5 is a major hurricane
- Wind speed is measured
How is Rainfall Measured?
Flood Discharge
- Volume of water that passes a particular area per second
- Discharge can indicate changes to pattens in precipitation or change to the river’s channel capacity, as well as measuring the severity of a flood
What is the Hazard Risk Equation
Risk = Hazard x Vulnerability / Capacity to cope
What is a Disaster
A serious disruption of the functioning of the community or society involving human, material, economic and environmental losses which exceed the ability of he affected community or society to cope using its own resourced
Distribution of Geophysical Hazard
Constructive and Destructive plate boundaries - Volcanoes and earthquakes
Collision plate boundary - Earthquakes
Middle of plates (intra-plates) with pre existing weaknesses which because reactivated, forming seismic waves / earthquakes
Location of Hydro-meteorological Hazards
Hurricanes affect coastal settlements in warm bodies if oceans
Flooding will occure more often for retreating coastline, rivers and melting glaciers
Droughts occure in Saharan or semi-arid climates
How do humans impact disaster rate/ vulnerablity?
Rapid Population Growth
- More vulnerable people on the planet
- Pressure of land =more hazards
Deforestation and Land Degradation
- Soil becomes saturated quicker, leading to land slides and Flooding
- Destruction of mangroves= more coastal flooding
- Desertification
Urbanisation
- Squatter settlement
- Greater number of vulnerable people in one area. Puts pressure on services
Poverty and Politics
- Developing contries do not have money to build appropiate infustructure and are therefore effected more
- Education in poorer counartys is less, and therefore higher vulnerablitlty
- Corrupt governments may misuse or prevent money going into to mitigation, recovery and responce
What is a Hazard Hotspot?
A location or region that is particularly prone to experiencing high frequency or intensity of natural hazards
What area are Hazard Hotspot?
- Coastlines (hurricanes and tsunamis)
- fault lines (earthquakes)
- Human activity (deforestation, urbanisation)
- Mountainous regions (Landslides, Avalaunch)
Economic Impact of Natural Disasters
infrastructure damage - high repair and reconstruction costs
Loss of life and injury - healthcare expenses
Disruption of economic activity
Impact on agriculture and food security - price increase for consumers due to supply and demand
Social Impacts of Natural Disasters
Loss of life
Displacement and homelessness
Disruption of communities
Impact on mental health
Disruption of education
Increase vulnerability
Impact on cultural heritage
Environmental impacts of a Natural Disaster
Habitat destruction
Soil erosion
Air pollution
Deforestation
Water pollution
What is a Mega-disaster?
A large scale disaster that causes extensive damage, loss of life and significant social, economic and environmental impacts.
Mitigation
Mitigation identifies the characteristics of the potential hazard and what can be done to reduce their impact on people, such as:
- Land use zoning
- Building codes and regulation
- Protective defences
Preparedness
Preparedness involves minimising loss of life and property
- Developing prepardness plans
- Developing warning systems
- Stokiling medicine, food, water
- Education, training, drills
Response
Coping with a disaster, main aims would be to rescue people and reduce economic losses:
- Search and rescue efforts
- Evacuating people
- Restoring vital infrastructure like water and electricity
- Restoring vital services like law enforcement and health care
How do you measure the severity if a disaster?
Hazard profiling
compare characteristics including
- speed of onset
- Economic loss
- Magnitude
- Frequency
- Fatalities
- Aerial Extent
- Spacial Predictability
- Durration
What is difference between macro modification and micro modification
Macromodification -Large scale support and protective measures designed to protect whole comunities
Micromodification -Strengthening individual buildings and structure
What are the diffrent types of modification
Land use zoning
- preventing buildings on low lying areas and areas of high risk
Resistant buildings
- buildings with deep foudnations, sloped roofs so that ask doesn’t build and create pressure
Tsunami/storm surge defences
- Sea walls which stop waves travelling inland
Lava diversion
- Barriers and water cooling to divert and slow down lava flow
Advantages and Dis
