Hazards Flashcards
What is a natural hazard and a disaster?
A natural hazard is a perceived event that threatens both life and property and could cause disruption to human systems (e.g. communication)
A disaster occurs when a hazard causes severe harm to a community
What are the different types of hazards?
Geophysical hazards originate from the solid earth and driven by the Earth’s internal energy
Atmospheric hazards originate in the atmosphere, driven by meteorological and climatic processes
Hydrological hazards originate in surface and subsurface freshwater and saltwater, driven by processes in water bodies
Why does vulnerability to a hazard vary?
Vulnerability may vary over time and space because wealth and technology play a huge part in the impacts of a natural hazard event.
Richer countries are more able to protect themselves (e.g. effective emergency services), more aware of risks through education.
Poorer countries are extremely vulnerable as urban areas grow so rapidly it forces people to live in hazardous conditions (e.g. on steep hill sides which exposes them to landslides)
Why do people forcibly make themselves vulnerable to hazards?
People may make themselves vulnerable by living in high risk areas because:
- The events are unpredictable (magnitude and frequency)
- Lack of alternative (social, economical and political factors may prevents someone from moving)
- Level of risk may have changed over time (more hazardous, e.g. deforestation of rainforests increases risk of flooding)
- The benefits of living there may outweigh the losses
- The perception of the individual (e.g. fatalism)
What are the perceptions to hazards?
Fatalism: a view of a hazard event that suggests that people cannot influence the outcome, nothing can be done to mitigate it
Adaptation: attempts by people/communities to live with hazard events by adjusting their living conditions which reduces their level of vulnerability
What are some characteristics that can influence hazard perception?
- socio-economic status (e.g. in wealthier areas there is a sense of being prepared and preventing disaster whilst deprived areas look at it as a way of life)
- Level of education
- Occupation/employment status
- Religion, culture and ethnic background
- Family status
- Past experience
- Values, personality and expectations
What are the perception responses to hazards?
Fatalistic perception makes people believe their fate is at “God’s Will” so the losses are inevitable and any mitigation/prevention is futile
Adaptation perception leads to people preparing, predicting and protecting with the available technology or funds of the area, due to the belief they can survive
Fear pushes people to move away as they will feel to vulnerable to any event, unable to live there)
Hazard perception case study: Haiti
Haiti perception to natural hazards in fatalistic, nothing can be done to mitigate hazards
Economic characteristics:
- Poorest country in the Western hemisphere
- Poor quality of settlement
- Corrupt and poor government
Cultural characteristics:
- Heavy voodoo beliefs (mixture between Catholicism and African beliefs) where God determines when a person lives and dies (God’s Will)/ destiny decided life
- Hope in the next life things will be better (escape poverty)
What is distribution, frequency and magnitude?
Distribution: refers to the spatial coverage of the hazard
- Can have a very localized effect or a global effect
- Can reference the area where the hazard is likely to occur
Frequency: The distribution of a hazard through time
Magnitude: the assessment of the size of the impact of a hazard event
What are primary and secondary effects?
Primary effects are the impacts that are directly caused by the natural hazard event whilst Secondary effects are a direct results of the primary effects
Name 3 human responses to the threat of hazards?
- Risk Sharing involves prearranged measures that aim to reduce the loss of life and property damage through public education, awareness programmes, evacuation procedures and provision of emergency supplies
- Integrated Risk Management: the process of considering the social, economic and political factors involved in risk analysis and deciding actions that should be taken to minimize damage
- Prediction: the ability to give warnings so that action can be taken to reduce the impacts of hazard events
What is the DEGG model?
Analysing the impact, which element had the biggest impact (whichever circle in bigger gives the best explanation of why a hazard became a disaster), how the 2 elements are involved in the outcome
Characteristics of hazard/ evidence of disaster/ characteristic of place
What is the hazard risk equation?
Analyses the risk (loss of property/life etc)
- Shows how all the elements interact with each other (complexity)
- Judgement of how risky a hazard is becoming a disaster
What is the hazard management cycle?
4 stages of preparedness, response, recovery and mitigation
Teaches us how people are responding to hazards and shows how they can improve effective management. Allows us to analyse the response (what was positive and negative) and evaluate the management (what they did, when and anything they left out).
What is the park model/disaster response curve?
Teaches us how effective is the management response is, how well do they prevent or improve quality of life and evaluate the response over time.
Evaluate the recovery/resilience/response/management…
- If a region is more prepared for a natural hazard event, the less the quality of life will fall!
What determines explosivity of a volcano?
The explosivity of a volcanic eruption is determined by the viscosity of the lava (how well the lava flows)
Basaltic lava – low viscosity, less silica
Andesitic Lava – high viscosity, traps gas, builds pressure, more explosive
Rhydilic lava
- Abundance of silica polymers leads to high viscosity
- Shape and characteristics of volcano are determined by lava
What are the different types of volcanoes?
Volcano types: Shield Composite/Stratovolcano Fissure Dome Ash-cinder Caldera
Assess the extent to which people’s perception of hazards is likely to effect their responses to them [9 marks]
HOW THIS IS MARKED:
- outlining different perceptions of hazards
- how perceptions relate to the responses
- how do other factors affect their response to hazards (e.g. wealth may allow someone to protect themselves or be helpless and education gives awareness to those in hazardous areas)
- short conclusion of how far perception of hazards affect responses
What is an ocean ridge?
Underwater constructive plate boundaries move apart allowing magma to force its way to the surface, consequently cooling to form new crust (ocean ridge). New crust is forcing down on the plate causes sea floor spreading, with the added force on the end of the plate being subducted.
Iceland has the mid-Atlantic Ridge passing through it and has fairly gentle sided volcanoes from the low viscosity of basaltic lava with frequent but gentle eruptions
How do volcanoes form generally?
The deeper a plate descends in a subduction zone, the hotter the surroundings become in the mantle and that mixed the friction, the oceanic plate melts into magma in the Benioff Zone. This less dense magma starts to rise as plutons, reaching the surface to form volcanoes.
What is a rift valley?
At constructive plate margins across continental areas the brittle crust falls apart (as it moves apart) and areas of crust drop between parallel faults forming rift valleys. Crust is much thinner, suggests that the tension within the crust is causing it to thin. Through the thinning, separating crust magma forces upwards creating composite, active volcanoes along the East African Rift.
What are island arcs?
A concentration of radioactive elements below the crust creates a hot spot. This causes plumes of rising magma to eat into the plate above, lava breaks through the surface and forming shield volcanoes as the basaltic lava flows slowly but far.
As the hot spot is stationary but the plate above moves a island arc/line of volcanoes is formed, for example the Hawaiian Islands, the older volcanoes put so much pressure on the crust subsidence has occurred.
E.g. West Indies and Hawaiian islands
How is the magnitude of volcanic eruptions measured?
The magnitude of volcanic eruptions are measured by the VEI scale (Volcanic Explosivity Index), scale of 0 to 8 (logarithmic scale). Critics do point out that it doesn’t take into account the amount of gas emitted
What are the primary effects of a volcanic eruption?
Lava Flows
Tephra (volcanic bombs of fine ash)
Pyroclastic flows (formed of hot gas over 800 degrees and tephra, can travel up to 700km/h)
Volcanic Gases (includes CO2, CO, hydrogen sulphide, sulphur dioxide and chlorine, can be fatal)
What are the secondary effects of a volcanic eruption?
Climatic change Acid Rain Floody (ice caps or glaciers melt) Landslides Lahars (volcanic ash mixing with water and flowing downhill) Tsunami
Do volcanic hazards show a relationship between hazard intensity and areal extent?
- Primary hazards tend to have a small areal extent but a high hazard intensity
- Secondary hazards tend to have a large areal extent and a lower hazard intensity
- However lahars and tsunamis have a much higher hazard intensity and a large areal extent
How can people prepare for a volcanic eruption?
- emergency evacuation plan
- education
- allows for a shorter recovery time
How can people protect themselves from volcanic eruptions?
- Identifying areas of the highest risk and land use planning completely avoids building in high risk areas
Digging trenches, dropping blocks into lava and using explosives are all methods to divert lava from settlements/gives people a longer time to evacuate
- In Hawaii they have barriers across valleys to protect environment
How can people predict a volcanic eruption?
Warning Signs:
- land swells
- hundreds of very small earthquakes (use a seismometer to detect any earthquakes)
- higher sulphur content in gas emissions (gas samples and chemical sensors can measure levels)
- temperature volcano rises (thermal imaging techniques and satellite cameras)
