Hazards Flashcards
What is a hazard?
“A hazard is a perceived natural event which has the potential to threaten both life and property.”
What is a disaster?
“A serious disruption of the functioning of a community or a society involving widespread human, material, economic or environmental losses and impacts, which exceeds the ability of the affected community or society to cope using its own resources.”
Simple explanation : a hazard that has enormous impacts on people and property
List some examples of hazards
Earthquake, tsunami, floods, acid rain, volcanoes, hurricane/cyclone/typhoon, mudslide (lahars), storm (tropical/snow/sand), sink hole, pandemics, lightning, tornado, wildfires, heatwaves, mud volcanoes, rockfall, climate change, avalanches, geyser etc.
What are the three classifications of hazards?
- Geophysical -> driven by Earth’s internal energy sources e.g. volcanoes
- Atmospheric -> driven by processes in the atmosphere e.g. wildfires
- Hydrological -> driven by water bodies, mainly oceans e.g. floods
What are the common characteristics of natural hazards?
- Little or no warning
- Clear origin or distinctive effects
- Exposure to risk
- Scale and impact requires emergency response
- Most damage and loss of life occurs shortly after the hazard but impacts may last into the future
How can impacts of hazards be classified?
They can be classified as primary or secondary:
Primary -> direct result of the hazard - they are immediate e.g. ground shaking in an earthquake (seismic activity)
Secondary -> occur after the event has occurred or as a result of the primary hazard e.g. collapsed buildings
What are the responses to natural hazards?
1. Fatalism - people believe they cannot influence the outcome of the event and so do nothing to prevent/manage it
2. Adaptation - attempts of the communities/people to live with the hazard events (adjustments to living conditions)
3. Fear
What is risk sharing?
A form of community preparedness, whereby the community shares the risk posed by a natural hazard and invests collectively to mitigate the impacts of future hazards
State the Disaster Risk Equation
RISK = HAZARD x VULNERABILITY
——————————
MANAGEMENT
What factors may lead to vulnerability?
Physical (age, disability),
Social (carer, family),
Economic (job),
and Environmental (level of land).
Potentially cultural and political factors as well as knowledge.
What factors influence hazard perception?
- Socio-economic status
- Level of education
- Employment status
- Religion, cultural background
- Family situation
- Past experience
- Personal values and personality
What is magnitude?
The size of the hazard.
What is intensity?
The power of a hazard i.e how strong it is and how damaging the effects are.
What is The Park Model?(RRR)
It is a model that shows the steps carried out in the recovery of a hazard, giving indication of time frame.
The steepness of the curve shows how quickly an area deteriorates and recovers.
The depth of the curve shows the scale of the disaster (the lower the curve, the lower the QoL)
Stage 1 - Relief (hours, days)
Immediate local response
Appeal for foreign aid
Stage 2 - Rehabilitation (days, weeks, sometimes months)
Services begin to be restored
Temporary shelters and hospitals
Food and water distributed
Foreign aid
Stage 3 - Reconstruction (weeks, years)
Infrastructure rebuilt
Area back to normal
Same or better QoL
Evaluation
✓ Shows link between Quality of Life and hazardous events
☓ Very generalised with no quantitative data
✓ Focuses on relief, rehab and reconstruction which helps understanding recovery
✓ Good for comparing different events and responses
☓ Does not examine that some countries need more help than others from outside
☓ Doesn’t address level of development/wealth
What is The Hazard Management Cycle?(PPRR)
The Hazard Management Cycle outlines the stages of responding to events.
- Prevention and Mitigation - strategies to lessen the effects of another hazard e.g. barriers, warning signals, risk assesment, planning
- Preparation - being ready for an event to occur e.g. public awareness, education, training
- Response - immediate action taken after event e.g. evacuation, medical assistance, rescue
- Recovery - long-term responses e.g. reconstruction, restoration of infrastructure & services
Evaluation
☓ Too generic and unquantifiable
✓ Easy to remember four-stage sequence
✓ Centered around 4 Ps: prediction, prevention, protection and preparedness
☓ Not as much detail as Park Model
✓ Place detail can be inserted into the model
What is Continental Drift and who proposed it?
It was first proposed by Alfred Wegener in 1915.
It states that the Earth’s crust is divided into continental and oceanic areas. The proportion of continental areas has increased through geological time and so have the positions of them and the oceans.
The evidence for continental drift is as follows:
- Jigsaw fit
- Tectonic fit
- Geological fit
- Glacial deposits
- Palaeo-climates and lithologies
- Fossil distributions
- Palaeo-magnetism
How is the Earth structured?
It has a layered structure…
- The outer layer of crust/lithosphere
- The asthenosphere
- The mantle
- Outer core
- Inner core at the centre of the Earth
What are convection currents?
They occur within the molten rock in the mantle. Liquid rock close to the core is heated and rises as it is less dense. When it reaches the crust it is forced sideways as it often cannot pass through the crust. The friction between the convection current and the crust causes the tectonic plate to move. The liquid rock then sinks back towards the core as it cools and the process repeats.
What is the Earth’s crust made of?
Continental Crust
- Thick (10-70km)
- Buoyant (less dense than oceanic crust)
- Mostly old
Oceanic Crust
- Thin (~7km)
- Dense (sinks under continental crust)
- Young
What happens at constructive boundaries?
The plates move apart leading to new material erupting to fill the gap in the form of a shield volcano.
What happens at destructive boundaries?
The plates move towards each other. This usually involves a continental plate and an oceanic plate. The oceanic plate is denser than the continental plate. As they move together, the oceanic plate is forced underneath the continental plate. This is called a subduction zone.
What happens at conservative boundaries?
The plates move parallel to each other. As the plates move, friction occurs and plates become stuck. Pressure builds up because the plates are still trying to move. When the pressure is released, it sends out huge amounts of energy, causing an earthquake. The earthquakes at a conservative plate boundary can be very destructive as they occur close to the Earth’s surface. There are no volcanoes at a conservative plate margin.
What volcanoes form at constructive plate boundaries and what are their eruptions like?
Shield volcanoes
- Basaltic lava which is high in temperature
- Low silica and gas content
- Non-acidic
- Runny lava
- Less viscous lava (sticky)
- Less violent eruption
- Shorter periods between eruptions
Fissure volcanoes
- Low viscousity
What volcanoes form at destructive plate boundaries and what are their eruptions like?
Composite volcanoes
- Violent eruptions
- Highly viscous lava (sticky)
- Acidic
- Longer periods between eruptions
- Andesitic lava which is lower in temperature and has more silica
What are trenches?
Trenches are long, narrow depressions on the seafloor that form at the boundary of tectonic plates where one subducts under the other (destructive plate boundaries) e.g. the Mariana Trench
How are volcanic hotspots formed?
Volcanic hotspots are formed by a localised plume of rising, hot mantle which partially melts the overlying plate due to the reduction in pressure.
Because magma is less dense than solid lithosphere it rises up and erupts onto the surface, cooling as it hits the ocean which creates active volcanic islands.
As the plate moves over the plume the volcanic island is carried away, becoming extinct due to it being removed from its magma source. A new volcanic island is formed above the hotspot to fill the gap and the process repeats, forming a chain of volcanic islands. The old islands subside as they are carried away, those under the sea forming guyots. An example of a volcanic hotspot is the Hawaiian Islands.
