Concept and nature of natural hazards

Hazard

A perceived event that causes loss of life, damage to properties, environmental harm, and disrupts human activities.

Vulnerability

The potential for loss due to exposure to hazards combined with an inability to cope with them

why stay? Lack of alternatives, benefit- willing- volcanoes tourism, changing levels of risk

vulnerability causes- wealth and level of technology , education and topography

Adaptation

Responding to hazards by preparing, adjusting, and making changes to reduce vulnerability.

Plate Tectonics

The theory explaining the movement of Earth's lithosphere plates, including continental drift, sea floor spreading, and subduction.

Natural hazards forms

Geophysical- earths core processes- volcanoes and earthquakes

Atmospheric- energy from sun drives processes in atmosphere- solar radiation- wildfire, tropical storms- changing- carbon budget, decreasing output

Hydrological- energy from sun drives processes in the hydrosphere- flooding

Hazard perception

Fatalism- nothing can be done

Eg- Haiti economic- one of poorest nations in world, subsistence farming- poor income, cant afford to build houses that will last seasonal rain

Cultural- voodoo- god determines when people die, hope in afterlife, live 16 times 

Adapatation- respond by preparing.

 Eg- LA- economic- largest economy in usa, $5 mil on earthquake proof building

Culture- resilient community, religious beliefs- optimistic

Fear- so vulnerable- move away

Park model

Collects info on the impact of the hazard on the quality of life and the impact of the management in the relief, rehabilitation and reconstruction stages on quality of life.

Use to evaluate how much quality of life was affected and how resilient and vulnerable the place is.

Hazard management cycle

The hazard management cycle is continuous loop which explains an

approach to managing a known hazard

preparedness, response, recovery, mitigation

Collects info on the hazard management actions in a place and the timing of management relative to the hazard event- pre, during, post

- preparation to reduce vulnerability- learn from past

Use to evaluate community preparedness and have they learnt from previous event.

Park model and hazard management positives and negatives

+ learn from past events, guide for air and reconstruction, improve resilient, evaluate success

- countries have varying capacity to prepare, prep can be overwhelmed by scale of hazard- Japan tsunami 2011, prep can be overwhelmed by human factors- typhoon Haiyan 

Earths structure

Centre- core- dense rock containing iron and nickel, solid inner and very hot molten outer

Mantle- thickest layer- molten/semi molten- upper and more fluid- asthenosphere

Lithosphere- upper mantle and crust

Outer- crust

Oceanic- less thick, younger, heavier

Continental- thicker, older, lighter

internal energy sources

Primordial- heat lost from earth as it continues to cool from original formation.

Radiogenic heat- heat produced by radioactive decay in mantle and crust

Most heat is found in a liner pattern in the centre of the Atlantic, Indian and Southern Ocean

Lowest heat concentrated in large land masses  

Continental drift

Continental drift-1910s- Alfred Wegner- todays continents are formed from the splitting of Pangaea (one large continent)  

+ geological evidence- fit of south America and west Africa, biological evidence- fossils found in India and Australia are compatible. 

- can’t explain how continents move

Sea floor spreading

Sea Floor spreading-1940s- creation of new land at mid ocean ridges- spreading ocean plates away from centre.

+ magnetic strips due to palaeomagnetism mirrored exactly either side of mid ocean ridge.

- can’t explain how space for new land is created and the speed of plate movement

subduction

Subduction- 1960s- if land is created at mid-ocean ridge, then it must be destroyed at the ocean margin. 

+ huge oceanic trenches where large areas of ocean floor are pulled downward.

- speed of plate movement is faster than can be explained

convection currents

Convection currents- 1980s- the circulation of magma due to thermal convection currents makes the crustal plat move.

+ unequal temp at surface indicates where hotter magma is rising, and cooler magma is sinking. 

- not be proven- can’t access mantle  

ridge push

Ridge push- the pushing force that plates experience as they slide down the raised asthenosphere underneath Mid Ocean Ridges.

slab pull

Slab pull- denser oceanic plate sinks into mantle at subduction zones. 

gravitational sliding

Gravitational sliding- constructive margins have elevated altitudes because of the rising heat between them which creates a slope- oceanic plate slides into

Destructive plate boundary

(convergent)

Plates move towards each other.  

Oceanic + constructive= oceanic plate is forced under continental, as it sinks plate melt due to friction in the subduction zone

Constructive plate boundary

(divergent)

Two plates move away from each other.

Magma rises through the asthenosphere tot eh surface, as this newly formed rock gets older the gravity causes it to slide away from the ridge.

Conservative plate boundary

young fold mountains

destructive plate boundary, The movement of the two plates forces layers of sedimentary rock upwards into a series of folds.

continental fold mountain formation- crust is less dense, forced together with a crumpling effect- continental mass is warped and forced upwards

continental and ocean crust whereby the more dense ocean crust is forced into the mantle- leading to uplift of the continental crust- andes

Earthquakes, landslides, and volcanoes

Eg- Himalayas

rift valley

A rift valley is a linear shaped lowland- formed because of the pulling apart of the lithosphere- constructive plate.  

earthquakes, volcanoes

eg- west Atlantic rift

ocean ridges

constructive, magma rises as plates move away from each other- less dense

earthquakes, volcanoes    eg- mid Atlantic rift

deep sea trenches

destructive, point at which the oceanic plate is subducted and melts

earthquakes and volcanoes

eg- Mariana trench

island arcs

destructive- magma rises at melting zone- volcanic arc

earthquakes, volcanoes, landslides

Mariana islands

magma plumes

Localised heating causes at plume of magma to rise through he mantle and eats into the crust

Where lava breaks through- volcanoes form

As plates move the volcanoes moves until eventually becoming extinct

Volcano leaves hot spot tracks where islands can form 

Eg- the Hawaii island chain- 6,000km chain of volcanic islands

Limitations- cant be applied to all volcanic activity

hazard response- risk sharing

working together to reduce the risk and sharing the costs of hazard response – for example buying home insurance – only some people need to claim but the cost is shared by everyone

hazard response- integrated risk management

analysing potential risks and implementing a coordinated approach to manage and reduce risks

adaptation

changing behaviour to reduce potential losses – examples include improving awareness of hazards and practising earthquake drills