Concept of a hazard
A hazard is a potential threat to human life and property caused by an event.
There are three major types of geographical hazard:
There are three major types of geographical hazard:
human response to hazards
Perception
People have different viewpoints of how dangerous hazards are and whatriskthey pose. These perceptions are dependent on lifestyle factors such as economic and cultural factors. For example, a person who is wealthy is perhaps less likely to view a hazard as dangerous as they may have the money to respond to it.
Response
Fatalism: The viewpoint that hazards are uncontrollable natural events, and any losses should be accepted as there is nothing that can be done to stop them.
Prediction: Using scientific research and past events in order to know when a hazard will take place, so that warnings may be delivered and impacts of the hazard can be reduced. In some cases, hazards may also be prevented when predicted early enough. (e.g. predicting wildfires from climatic red flags)
Adaptation: Attempting to live with hazards by adjusting lifestyle choices so that vulnerability to the hazard is lessened. (e.g. earthquake proof houses.)
Mitigation: Strategies carried out to lessen the severity of a hazard (e.g. sandbags to offset impact of flooding)
Management: Coordinated strategies to reduce a hazard’s effects. This includes prediction, adaptation, mitigation. 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.
These responses are all affected by the aspects of hazards. For example, higher magnitude hazards will clearly require moremanagement.Low incidence hazards will be harder to predict, etc
People have different viewpoints of how dangerous hazards are and whatriskthey pose. These perceptions are dependent on lifestyle factors such as economic and cultural factors. For example, a person who is wealthy is perhaps less likely to view a hazard as dangerous as they may have the money to respond to it.
Response
Fatalism: The viewpoint that hazards are uncontrollable natural events, and any losses should be accepted as there is nothing that can be done to stop them.
Prediction: Using scientific research and past events in order to know when a hazard will take place, so that warnings may be delivered and impacts of the hazard can be reduced. In some cases, hazards may also be prevented when predicted early enough. (e.g. predicting wildfires from climatic red flags)
Adaptation: Attempting to live with hazards by adjusting lifestyle choices so that vulnerability to the hazard is lessened. (e.g. earthquake proof houses.)
Mitigation: Strategies carried out to lessen the severity of a hazard (e.g. sandbags to offset impact of flooding)
Management: Coordinated strategies to reduce a hazard’s effects. This includes prediction, adaptation, mitigation. 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.
These responses are all affected by the aspects of hazards. For example, higher magnitude hazards will clearly require moremanagement.Low incidence hazards will be harder to predict, etc
park model
● Graphical representation of steps carried out in hazard recovery
● Rough indication of time frame.
● Can be used in comparing hazardous events (e.g. a hazardous event that is in a low income country will have a longer recovery time).
● The steepness of the curve shows how quickly an area deteriorates and recovers.
● The depth of the curve shows the scale of the disaster (i.e. lower the curve, lower the quality of life).
● Rough indication of time frame.
● Can be used in comparing hazardous events (e.g. a hazardous event that is in a low income country will have a longer recovery time).
● The steepness of the curve shows how quickly an area deteriorates and recovers.
● The depth of the curve shows the scale of the disaster (i.e. lower the curve, lower the quality of life).
The Park Model of Human Response to Hazards
hazard management cycle
The Hazard Management Cycle outlines the stages of responding to events, showing how the same stages take place after every hazard.
plate tectonics
Plate tectonic Theory
The lithosphere is broken up into large slabs of rock called tectonic plates.
These plates move due to the convection currents in the asthenosphere, which push and pull the plates in different directions. Convection currents are caused when the less dense magma rises, cools, then sinks. The edges of where plates meet are called plate boundaries (or plate margins).
Different plate boundaries At plate boundaries, different plates can either move towards each other (destructive plate margin), away from each other (constructive plate margin), or parallel to each other (conservative plate margin). Different landforms are created in these different interactions. This spider diagram outlines what landforms and processes occur at the boundaries:
The lithosphere is broken up into large slabs of rock called tectonic plates.
These plates move due to the convection currents in the asthenosphere, which push and pull the plates in different directions. Convection currents are caused when the less dense magma rises, cools, then sinks. The edges of where plates meet are called plate boundaries (or plate margins).
Different plate boundaries At plate boundaries, different plates can either move towards each other (destructive plate margin), away from each other (constructive plate margin), or parallel to each other (conservative plate margin). Different landforms are created in these different interactions. This spider diagram outlines what landforms and processes occur at the boundaries:
Hotspots
Hotspots are areas of volcanic activity that are not related to plate boundaries. Hot magma plumes from the mantle rise and burn through weaker parts of the crust. This can create volcanoes and islands. The plume stays in the same place but the plates continue to move, which sometimes causes a chain of islands (such as Hawaii).
Hotspots are areas of volcanic activity that are not related to plate boundaries. Hot magma plumes from the mantle rise and burn through weaker parts of the crust. This can create volcanoes and islands. The plume stays in the same place but the plates continue to move, which sometimes causes a chain of islands (such as Hawaii).
Hazards caused by volcanoes:
● Lava flows
● Lahars (mudflows) - caused by a number of reasons, usually by melting ice at high latitudes
● Floods - from melting ice sheets or glaciers at high latitudes
● Tephra - any type of rock that is ejected by a volcano
● Toxic gases - released during some eruptions
● Acid rain - caused when gases such as sulfur dioxide are released into the atmosphere
● Nuées ardentes/pyroclastic flows - clouds of burning hot ash and gas that collapses down a volcano at high speeds
● Lava flows
● Lahars (mudflows) - caused by a number of reasons, usually by melting ice at high latitudes
● Floods - from melting ice sheets or glaciers at high latitudes
● Tephra - any type of rock that is ejected by a volcano
● Toxic gases - released during some eruptions
● Acid rain - caused when gases such as sulfur dioxide are released into the atmosphere
● Nuées ardentes/pyroclastic flows - clouds of burning hot ash and gas that collapses down a volcano at high speeds
Hazards can be responded to by preventing them directly, being prepared for the next hazard, mitigating the effects of the hazard, or completely adapting your lifestyle to limit the hazard’s effects.
Seismic Hazards
● Plates do not move in fluid motions
● At any boundaries, plates become stuck due to the friction between plates
● The pressure builds so much that it cannot be sustained and the plates eventually give way
● The pressure is released quickly, causing a jolting motion in the plates
● This jolt is responsible for seismic movement spreading throughout the ground
● The focus is the point underground where the earthquake originates from
● Plates do not move in fluid motions
● At any boundaries, plates become stuck due to the friction between plates
● The pressure builds so much that it cannot be sustained and the plates eventually give way
● The pressure is released quickly, causing a jolting motion in the plates
● This jolt is responsible for seismic movement spreading throughout the ground
● The focus is the point underground where the earthquake originates from
Hazards caused by seismic events:
● Shockwaves (seismic waves) - energy released from the sudden jolt that vibrates through the ground
● Tsunamis - caused when water is displaced from plates moving underwater, creating a large wave
● Liquefaction - When soil is saturated, the vibrations of an earthquake cause it to act like a liquid. Soil becomes weaker and more likely to subside when it has large weight on it
● Landslides and avalanches
● Shockwaves (seismic waves) - energy released from the sudden jolt that vibrates through the ground
● Tsunamis - caused when water is displaced from plates moving underwater, creating a large wave
● Liquefaction - When soil is saturated, the vibrations of an earthquake cause it to act like a liquid. Soil becomes weaker and more likely to subside when it has large weight on it
● Landslides and avalanches
storm hazards
Tropical storm: a low pressure, spinning storm with high winds and torrential rain.
Conditions for a storm to form:
● Temperature: Ocean temperatures must be around 26 - 27°C to at least 50 metres deep.
● Rotation: Forms around the equator but no less than 5° on either side.
● Air pressure: Must be in areas of unstable air pressure - usually where areas of high pressure and low pressure meet (convergence) - so that warm air rises more readily and the clouds can form.
Conditions for a storm to form:
● Temperature: Ocean temperatures must be around 26 - 27°C to at least 50 metres deep.
● Rotation: Forms around the equator but no less than 5° on either side.
● Air pressure: Must be in areas of unstable air pressure - usually where areas of high pressure and low pressure meet (convergence) - so that warm air rises more readily and the clouds can form.
