Hazards Flashcards
What is the VEI ?
Volcanic eruption index
What three things do the VEI measure ?
- Volume of ejecta
- Height of the eruption column
- Qualitative observations
GIve three criticisms of the VEI ?
- Gas emissions
- Atmospheric / climate impacts
- All tephra considered alike despite differences in densities and impact
Give five ways in which volcanic eruptions vary ?
- Frequency
- Magnitude
- Regularity
- Predictability
- Duration
What is a super volcano ?
An unusually large volcano having the potential to produce an eruption with major effects on the global climate and ecosystems.
What is tephra
Solid material of varying grain size ranging from volcanic bombs to ash all ejected into the atmosphere during a volcanic eruption that then falls back down.
What is pyroclastic flow
Very hot gas charged high velocity flows made up of a mixture of super-heated gas and tephra
What are lava flows
Molten rock that flows from a volcanic vent
What are volcanic gases
carbon dioxide, sulphur dioxide, hydrogen sulphide, carbon monoxide and chlorine
How are lahars formed
Melted snow and ice as a result of the eruption or heavy rainfall following an eruption combines with volcanic ash and forms mud flows.
How are tsunamis formed
Sea waves generated by violent volcanic eruptions underwater or pyroclastic flows/lahars/landslides displacing water which often result in much more widespread impacts than the volcano itself
How is acid rain formed
Volcanoes emit gases which include sulphur, this then combines with atmospheric moisture and results in acid rain.
What is climate change
The ejection of huge amounts of volcanic debris into the atmosphere can reduce global temperatures.
Sulphur dioxide emitted from volcanoes when combining with water vapour creates droplets of sulphuric acid which reflect sunlight.
What is the impact of a lahar
1985 - Nevado del Ruiz, Amero, Colombia - 23, 000 people killed. Impacts include: destruction of natural habitats/settlements/farmland; economic benefits of lahar deposits. Long-term impacts can occur many years post eruption.
What is the impact of a tsunami
Wide-spread destruction
What is the impact of acid rain
- Damages and kills trees
- Leaches toxic metals from soils and then accumulates in rivers/lakes
- Kills fish stocks and damages ecosystems
- Damages buildings and monuments by accelerating weathering
What is the impact of climate change
Unusually cold weather > crop failures and resultant food shortages. The eruption of the Laki fissure system and ash/gas cloud has been linked to the start of the French Revolution in 1789
Give three methods of preparedness to reduce the risk of volcanic hazard
- Hazard mapping
- Have emergency kits prepared
- Set up search and rescue teams
Outline how the following warning signs of volcanic hazards can be predicted
Sulphur/radon gases
Ground deformation
Energy release
Surface temperature changes
Sulphur/radon gases = Spider robots
Ground deformation = Tiltmeters
Energy release = Seismometers
Surface temperature changes = Thermal Heat sensors
How do earthquakes result in tsunamis
Earthquakes vertically move the seabed up by several metres.
Displacing (moving) the water above. The greater the movement of the sea floor the greater the volume of water displaced and the bigger the wave produced - hence greater intensity at destructive plate boundaries as higher magnitude earthquakes.
Large waves radiate outwards across the ocean away from the epicentre of the earthquake.
In deep water no energy is lost to frictional drag with the seabed.
As wave approaches shore > water becomes shallower and the base is slowed down by friction, forcing the circular wave motion into an elliptical form, which heightens until it can no longer be maintained and breaks. This is called shoaling.
A large wave hits the coast, a tsunami.
How do the following factors affect the intensity of impacts of a tsunami?
The height of the waves:
The distance the waves have travelled:
Shape of coastline:
The height of the waves: the level of movement of the sea floor - the greater the movement the greater the volume of water displaced and the bigger the wave produced.
The distance the waves have travelled: waves lose energy as they travel towards the land, so the closer to the coast the waves start, the less energy they will lose, therefore tsunamis tend to be more powerful when they start closer to the coast.
Shape of coastline: Indented coastlines with long, narrow bays concentrate energy on the bay head due to a funnelling effect as the wave travels up the bay. Irregular coastlines and offshore islands can set up interference patterns in the waves which, when they coincide perfectly, can accentuate the waveform.
How do the following factors affect the intensity of impacts of a tsunami
Relief of coastline:
Presence of natural defences:
Population density
Relief of coastline: Cliffs present a natural barrier to a tsunami.
Presence of natural defences: Coral and mangroves act as natural defences by dissipating wave energy through their large surface areas.
Population density: High population density - greater intensity. Also, the young and old are the most vulnerable, and there may be a gender disparity.
What is a natural hazard ?
Naturally occurring phenomena that occurs in the lithosphere, hydrosphere and atmosphere. That is a threat to both life, the built and natural environment.
What are the three types of natural hazard ?
- Geophysical
- Hydrological
- Atmospherical
What are the five characteristics of natural hazards?
- Origins are clear and their effects are distinctive
- Most only offer short or little warning before the event
- Exposure to risk is involuntary in LIC and some NIC’s whilst in HIC’s they are aware of hazards however choose to minimise or ignore them
- Most losses to life and damage to property occurs shortly afterwards even though the effects of natural hazards can be felt in communities long after that time
-The scale and intensity of the event requires an emergency response
Define vulnerability
How susceptible a population is to damage caused by a hazard - potential for loss which varies over time and space.H
Define risk
The likelihood that people will be seriously affected by a hazard
Define multi-hazard environment
places where two or more natural hazards occur and may interact to form more complex disasters
Describe the spatial distribution of tropical storms
- 5-20N/S of equator
- Hurricanes: North Atlantic and NE pacific - Caribbean sea, Gulf of Mexico and Western Central America
- Cyclones: Southern Pacific/ Indian
- Typhoons: NW pacific affect SE Asia
- Found in areas with oceans over 27 C and 70+m deep, low level convergence of air in lower atmospheric circulation systems
Why do people consciously put themselves at risk of natural hazards?
- Hazard events are unpredictable - We cannot predict the frequency, magnitude or scale of a natural hazard event.
- Lack of alternatives - Due to social, political, economic and cultural factors, people cannot simply uproot themselves from one place and move to another, giving up their homes, land and employment.
- Changing the level of risk - Places that were once safe many have become through time far more at risk . - Cost/benefit - Advantages of living somewhere outweigh the disadvantages - Perception
Define fatalism
People cannot influence the shape or outcome therefore nothing can be done to mitigate against it. People with such an attitude put in place limited or no prevention measures. ‘God’s will’
Define adaptation
Attempts by people or communities to live with hazard events. By adjusting their living conditions to live with the hazards and to reduce their vulnerability.
Define mitigation
Attempts to lessen the severity of hazards.
Why is perception important in the context of hazards?
People’s perception will ultimately decide and determine the course of action that individuals take or the response they expect from governments and other organisations
What are the three ways people may perceive natural hazards?
Fatalism
Adaption
Fear
How does socioeconomic status affect perception of risk
Wealthier areas better prepared/protected/consider hazards more controllable/voluntary > lower risk. Poorer areas: less able to afford protections etc/may be involuntary, lack of alternatives means cannot move away > risk seems greater
How does level of education affect perception of risk
People with a better education may better understand the risk of hazards or believe they are able to reduce the risks.
How does religion affect perception of risk
If hazards are an act of god > people may perceive them as uncontrollable and be less likely to mitigate them
How does past experience affect perception of risk
Prison of experience - limit perception of risk to past experiences - more likely to fully understand. Vs ‘lightning never strikes the same place twice’ approach
Define community preparedness
Involves prearranged measures that aim to reduce the loss of life and property damage through public education and awareness programmes, evacuation procedures, the provision of emergency medical supplies and the taking out of insurance
Define integrated risk management
The process of considering the social, economic and political factors involved in risk analysis; determining the acceptability of damage/disruption; deciding on the actions to be taken to minimise damage/disruption
Define resilience
The ability of individuals or communities to be able to utilise available resources to respond to, withstand and recover from the effects of natural hazards events.
What are the four stages of the disaster risk management cycle ?
Preparedness
Response
Recovery
Mitigation
Give two positives and two negatives of the disaster risk management cycle
- Less reflective of slow onset disasters as no obvious event to trigger movement between stages
- Generic - no specific figures
+ Risk management is an ongoing process - hence a cycle.
+ Shows effects of preparedness before/after event
What are the five stages of the Park Model?
Pre-disaster
Disruption
Relief
Rehabilitation
Reconstruction
What does the following tell you about a country’s response to a disaster?
Depth of curve: intensity of impacts
Steepness of upward curve: Effectiveness /speed of recovery
Steepness of downward curve: type of hazard (rapid or slow onset).
The Park Model shows changes of ____ over time?
Quality of life
Give two positives and two negatives of the Park Model
- Doesn’t show quantitative data making comparisons difficult
- Doesn’t show pre-onset mitigation methods for example evacuation - so cannot compare these
+ Allows for comparison between events to show what was effective in recovery
+Helps planners plan for future events as can rehabilitate to a higher standard and implement mitigation strategies
Explain the rehabilitation stage of the Park model
Immediate impacts are under control so people start to resolve longer term problems
The distribution of a hazard through time is called the…
Frequency
The assessment of the size and impacts of a hazard event is known as the …
Magnitude
The ability of individuals to withstand and recover from a disaster is known as …
Resilience
How will incidence affect the level of management needed following a disaster
A high incidence = frequent, expected and more likely to have a management plan in place.
High incidence hazards also tend to be less intense > so less of a need for a large management response.
How will intensity affect the level of management needed following a disaster
High magnitude, high intensity hazards tend to have worse effects and therefore require more management
How will distribution affect the level of management needed following a disaster
areas with a high hazard distribution are likely to have lost management strategies, those living there will be more adapted to the hazardous landscape > less intense
How will a high level of development affect the level of management needed following a disaster
LICS less able to afford effective mitigation strategies > more disastrous/less management
How will a multi-hazard environment affect the level of management needed following a disaster
Lack of money for multiple hazards so may lack management strategies for the less frequent events.
What is prediction in the context of hazards?
Using scientific research and past events to forecast when and where hazards will occur and provide warnings to aid in evacuation to reduce the impacts of a hazard.
Give an example of methods of prediction.
The tsunami warning system
Give three factors needed to make prediction an effective management technique
- Information must be successfully distributed
- Information must be accurate
- Recipients must trust warnings and know how to effectively respond
What is ‘protection’ in the context of hazards?
Protect people from the impact of the event by modifications to the built environment
What are the three ways people and organisations manage natural hazards?
Prediction
Protection
Prevention
What is a primary hazard
Hazards that are directly related to the hazard event.
What is a secondary hazard
Hazards that occur due to the occurrence of another are indirectly related and occur after the primary hazard.
