PHYSICAL - Hazards

hazard

potential threat to ​human life​ ​and ​property​ caused by an event

three major types of geographical hazard

1. Geophysical
2. Atmospheric
3. Hydrological

Geophysical hazard

A hazard formed by tectonic/geological processes (Earthquakes, volcanoes and tsunamis).

Atmospheric hazard

* a natural hazard caused by extreme weather conditions such as hurricanes or tornadoes.


* potentially damaging natural event associated with changes in atmospheric conditions

Hydrological hazard

A risk posed by elements of water e.g. Flooding, Glaciers, Wave action etc.

Incidence

frequency of hazards

Intensity

the power/ strength of a hazard

Magnitude

the size of the hazard, usually this is how a hazard's​ intensity is measured

Distribution

where hazards ​occur

Level of development

economic development will affect how a place can respond to a hazard, so a hazard of the same magnitude may have very different effects in two places of contrasting levels of development

Human Responses to Hazards

* perception
* response

Perception

* different ​viewpoints of how ​dangerous hazards are and what ​risk ​they pose.
* dependent on ​lifestyle factors: ​economic ​and ​cultural ​factors.
* wealthy people are less likely to view a hazard as dangerous as they may have the money to respond to it.

response

* Fatalism

1) Prediction

2) Adaption

3) Mitigation

4) Management

5) Risk sharing

fatalism

the belief that all events are determined in advance by fate and cannot be changed by human means

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

​community preparedness​, whereby the community ​shares the risk posed by a natural hazard and ​invests collectively​ to mitigate the impacts of ​future hazards​.

The Park Model

* graph showing speed and magnitude at which quality of life declines after a hazard
* 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)

Stage 1 - Relief (hours - days)

● Immediate local response - medical aid, search and rescue.

* Immediate appeal for foreign aid - the beginnings of global response

Stage 2 - Rehabilitation (Days-Weeks)

* Services begin to be restored
* Temporary shelters and hospitals set up
* Food and water distributed
* Coordinated foreign aid - peacekeeping forces etc.

Stage 3 - Reconstruction (weeks-years)

● Restoring the area to the same or better quality of life

* Area back to normal - ecosystem restored, crops regrown
* Infrastructure rebuilt
* Mitigation efforts for future event

The Hazard Management Cycle

Model for measuring hazard management made up on 4 stages: preparedness, response, recovery and mitigation

preparedness

Being​ ready​ for an event to occur (public awareness, education, training)

response

Immediate action taken after event (evacuation, medical assistance, rescue)

recovery

Long-term responses (restoring services, reconstruction)

Mitigation

Strategies to ​lessen effects of another hazard(barriers, warning signals developed, observatories)

inner core

* A dense sphere of solid iron and nickel at the centre of Earth
* pressure & radioactive decay
* Earth's internal energy

outer core

semi molten iron and nickel

mantle

* The layer of hot, solid material between Earth's crust and core.
* top of the asthenosphere
* high silicon

Asthenosphere

The soft layer of the mantle on which the tectonic plates move due to convection currents

Lithosphere

* A rigid layer made up of the uppermost part of the mantle and the crust.
* broken up into plates

crust

* The thin and solid outermost layer of the Earth above the mantle
* Oceanic crust is ​dense and is destroyed by ​plate movement, continental crust ​is ​less dense and is not destroyed

Plate Tectonic Theory

* the theory that the lithosphere is broken up into large plates that move and then rejoin; considered the unifying theory of geology
* convection currents of magma

Destructive plate boundary

plates move towards each other

Constructive plate boundary

Plates that move away from each other

Conservative plate boundary

where two tectonic plates slide past each other

destructive -continental & continental

* Both plates are not as dense as oceanic so lots of pressure builds.


* Ancient oceanic crust is subducted slightly, but there is no subduction of continental crust.
* Pile up of continental crust on top of lithosphere due to pressure between plates.
* Fold mountains formed from piles of continental crust.

destructive - continental & oceanic

* Denser oceanic plate ​subducts ​below the continental


* The plate subducting leaves a deep ocean trench​.
* Built up ​pressure from the melting plate cause explosive volcanoes bursting through the​ continental plate​.

destructive - oceanic & oceanic

* Heavier plate ​subducts leaving an ocean trench.


* Built up pressure causes ​underwater volcanoes bursting through oceanic plate.
* Lava cools and creates new land called island arcs​.

constructive - continental & continental

* Any land in the middle of the separation is forced apart, causing a rift valley.


* Volcanoes form where the magma rises.
* Eventually the gap will most likely fill with water and separate completely from the main island.
* The lifted areas of rocks are known as horsts whereas the valley itself is known as a graben.

constructive - oceanic & oceanic

* Magma rises in between the ​gap left by the two plates separating​, 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 is known as​ ​sea floor spreading​ ​(as the floor spreads and gets wider).

Ridge push

when the force of gravity moves a plate downward and away from a ridge

Slap pull

When a plate ​subducts​, the plate sinking into the mantle ​pulls the rest of the plate (slab) with it, causing further subduction.

Hotspots

* 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)

Spatial Distribution (volcanos)

Along ​constructive ​or ​destructive ​plate boundaries, or located on ​hotspots​

Magnitude (volcanos)

Vulcanicity​ is measured using the ​Volcanic Explosivity Index​. The more powerful, the more ​explosive​.

Frequency (volcanos)

* varies per volcano.
* Volcanoes are classed as either active, dormant or extinct. ​An estimated ​50-60 volcanoes erupt each month, meaning volcanic eruptions are always frequent (and some volcanoes erupt constantly).
* The frequency of volcanic eruptions hasn't changed much in recent history.

regularity (volcanos)

eruptions are regular in that the eruptions on ​each type of boundary are similar (e.g. eruptions on destructive boundaries will regularly be more explosive than at constructive boundaries). Sometimes eruptions may be irregular and not fit patterns.

predictability (volcanos)

Regularity of eruptions can help estimate when eruptions will take place (i.e. every 10 years). Seismic activity, gases releasing, elevation etc. can all indicate an imminent eruption, but there is no ​definite​ predictions to a volcanic eruptio

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
* pyroclastic flows - clouds of burning hot ash and gas that collapses down a volcano at ​high speeds

Tephra

rock fragments and particles ejected by a volcanic eruption.

pyroclastic flow

the flow of ash, cinders, bombs, and gases down the side of a volcano during an explosive eruption

environmental effects (volcanos)

PRIMARY

* Ecosystems damaged​ through various volcanic hazards
* Wildlife killed

SECONDARY

* ​Water acidified by ​acid rain
* ​Volcanic gases contribute to greenhouse effect​ (global warming)

economic effects (volcanos)

PRIMARY

* ​Businesses​ and industries destroyed or disrupted

SECONDARY

* jobs lost
* profit from tourism industry

social effects (volcanos)

PRIMARY

* people killed
* homes destroyed form pyroclastic flows

SECONDARY

* Fires​ can start which puts lives at risk
* mudflows or floods
* trauma
* homelessness

political effects (volcanos)

PRIMARY

* ​Government buildings​ and other important areas destroyed or disrupted

SECONDARY

* ​Conflicts concerning government response, food shortages, insurance etc.

prevention (Volcanoes)

* cannot be prevented
* stop people going near

Preparedness (Volcanoes)

* education
* evacuation plans
* monitor volcanoes
* training

Mitigation (volcanoes)

* evacuation
* strengthen buildings

adaptation (volcanoes)

* move away
* encourage tourism

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

focus

The point beneath Earth's surface where rock breaks under stress and causes an earthquake

Spatial Distribution (earthquakes)

along all boundaries

magnitude (earthquakes)

Seismicity ​is measures using:

* the ​logarithmic Richter Scale​: measure of the strength of seismic waves.
* The ​Mercalli Scale: rate of the destruction caused.

frequency (earthquakes)

Earthquakes are frequent around the world and occur​ every day​ at boundaries. Hundreds of smaller magnitude earthquakes that cannot be felt by humans occur every day, whereas the larger earthquakes are less frequent.

predictability (earthquakes)

Earthquakes are almost impossible to predict. ​Microquakes​ may give some indication but the magnitude cannot be predicted as how strong they are is random​.

Shockwaves

energy released from the sudden jolt that vibrates through the ground

Tsnami

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

Slope failure as a result of ground shaking

environmental effects (earthquakes)

PRIMARY

* Earthquake can cause​ fault lines which destroy the environment
* liquefaction

SECONDARY

* Radioactive materials​ and other dangerous substances leaked from power plants
* Saltwater from tsunamis flood freshwater ecosystems-Soil ​salinisation

economic effects (earthquakes)

PRIMARY

* Businesses destroyed

SECONDARY

* ​Economic decline​ as businesses are destroyed (tax breaks etc.)
* High ​cost of rebuilding​ and insurance payout - Sources of income lost

social effects (earthquakes)

PRIMARY

* Buildings collapse​, killing/injuring people and trapping​ ​them.

SECONDARY

* Gas pipes rupture​, starting fires which can kill
* Water supplies are contaminated as pipes burst, spreading disease​ and causing floods
* Tsunamis which lead to ​damaging flooding

political effects (earthquakes)

PRIMARY

* Government buildings destroyed

SECONDARY

* Political unrest from food shortages or water shortages
* Borrowing money for international aid
* Can be initial chaos and '​lawlessness​' e.g. looting

prevention (earthquakes)

* protection against secondary disaster eg.landslides, rockfall, landslides and rock falls


* more security
* don't build in environments that have the potential disaster
* deep foundations of the buildings or allow for some flexibility inorder for it to move with the seismic waves

Preparedness (Earthquakes)

* education & awareness
* evacuation plans


* tsunami warning systems

mitigation (earthquakes)

* search and rescue
* demolish unsafe buildings
* sea walls

adaptation (earthquakes)

* move away
* earthquake proof buildings
* insurance

Tropical storm

​low pressure​, spinning storm with high winds and torrential rain

tropical storm conditions

● Temperature: ​Ocean temperatures must be around ​26 - 27°C ​to at least 50 metres deep. \n ● Rotation:​ Forms around the equator but no less than ​​5° on either side​. \n ● Air pressure:​ Must be in areas of ​unstable air pressure​ ​- usually where areas of high \n pressure and low pressure meet (​convergence​) - so that warm air rises more readily and the clouds can form

location of tropical storms

Only form over the sea. Usually occur between the latitudes 40°N and 40°S but never on the equator because the Coriolis effect causes the winds to spin away and towards the west. Most form in the Pacific Ocean.

Magnitude (tropical storms)

Measured on the ​Saffir-Simpson Scale ​(A scale of 1-5) based on wind speed and thus power of the storm.

frequency (tropical storms)

Northern Hemisphere from June-November, Southern Hemisphere from November-April. Tropical storms that are ​more powerful​ and reaching land are thought to be increasing in frequency.

regularity (tropical storms)

Tropical storms are ​irregular​ because although they occur in the ​same areas​, their path does not follow a set route - the route taken is ​dependent on the storm​ and the climatic conditions.

predictability (tropical storms)

Tropical storms form ​away from land​ meaning ​satellite tracking​ of cloud formations and movement can be tracked and the general route can be predicted.

Hazards caused by tropical storms

* High winds​ - over ​300km/h​ ​and therefore very strong
* Flooding ​- coastal/river flooding from ​storm surges​ and ​heavy rain
* Landslides​ - due to soil becoming​ heavy​ when wet with high levels of rain
* Storm surges​ - Large ​rise in sea levels ​caused by low pressure and high winds, pushing water towards the coast

environmental effects (tropical storms)

PRIMARY

* Beaches ​eroded
\-Sand displaced
* Coastal ​habitats such as coral reefs are destroyed

SECONDARY

* River flooding/ ​salt water​ contamination - ​Animals displaced from flooding e.g. alligators
* Water sources changing course from blockages

economic effects (tropical storms)

PRIMARY

* Businesses destroyed
* ​Agricultural land damaged
SECONDARY
* High cost of rebuilding ​and insurance​ payout
* Sources of income lost
* Economic decline from sources of income destroyed

social effects (tropical storms)

PRIMARY

* ​Drowning
* ​Debris ​carried by high winds can injure or kill
* Buildings destroyed

SECONDARY

* Homelessness


* ​Polluted water ​supplies spread disease
* Food shortages from damaged land

political effects (tropical storms)

PRIMARY

* Government buildings destroyed

SECONDARY

* Issues paying back international aid
* Pressure for government to do more about global warming

prevention (tropical storms)

-reduce climate change

preparedness (tropical storms)

* evacuation
* awareness
* satellite tracking
* warning systems

mitigation (tropical storms)

* search and rescue
* strengthen buildings
* remove loose debris

adaptation (tropical storms)

* move
* flood defences
* strom proof buildings

wildfire

A large, ​uncontrolled​ fire that quickly spreads through vegetation.

Conditions favouring intense wildfires

* Vegetation type
* Fuel characteristics
* Climate and recent weather
* Fire behaviour

vegetation type

* Thick, close together vegetation allows fires to spread ​quickly and easily. ​
* Trees and thick bushes ​lead to more intense wildfires; grasslands do not burn as intensely.
* Vegetation with flammable oils​ - like eucalyptus - causes more intense fires also.

Fuel characteristics

Vegetation should be ​dry to allow it to catch. ​Finer vegetation causes fires to spread quicker​, but larger,​ thicker ​forms of vegetation burns for longer and more intensely.

climate and recent weather

Must be in a climate that has ​enough rainfall to have sufficient plant growth​, but considerable dry spells and droughts to ​dry out the fuel​. Areas with ​dry seasons ​such as California allow for intense wildfires. ​Wind also causes fires to spread quicker. ​Recent temperature increases have caused an​ increase​ in the number of ​wildfires​.