Hazards 3.1.5.1 Flashcards
3.1.5.1-3.1.5.6
What is a natural hazard?
Natural hazard = A natural event with the potential to cause harm to people and to property
What is a natural disaster?
A natural disaster = The realisation of a natural hazard where harm has occured
When can a hazard be defined a disaster?
- 10 or more deaths have occured or when there is a declaration of an emergency by the relative government
- Insurance companies define it when economic losses exceed 1.5million
What can hazards be caused by?
- Human actions (explosions, chemical releases into atmosphere and nucler incidents)
- Natural (earthquakes, storms, volcanoes and wildfires)
- Natural events are often caused by human action e.g wildfires due to human carelessness
What factord affect the impacts of hazards?
-The location of rge hazard relative to areas of population and the magnitude and extent of the hazard
- Specifc to the type of hazard e.g. type and exposivity of a volcanoe, Nature and continental shelf and shoreline for tsunamis
What are geophysical hazard?
Geophysical= caused by the movement of tectonic plates, driven by the earths own internal energy
E.g. Plate tectonics, volcanoes, sesimic activity
What are atmospheric hazards?
Atmospheric = Caused by processes occurring in our atmosphere
E.g. Tropical storms, Droughts
What are hydrological hazards?
Hydrological = driven by water bodies, mainly the ocean
E.g. Floods, Storm surges, Tsunamis
What are primary impacts?
Primary impacts = Those that have an immediate effect on the affected area, such as destruction of infrastructure and contamination of water supplies
What are secondary impacts?
Secondary impacts = impacts that have occurred after the disaster has occurred such as disease, economic recession and contamination of water supplies
What is hazard perception?
Hazard perception = the way in which someone understands or interprets a hazard
What is hazard perception determined by?
- The effect that the hazard may have on our lives and this increases if people have a direct experience with a hazard and the long term impacts it caused
What are the negatives of urbanisation for hazards?
- The pressure of an increasing population and subsequent demand for land has resulted in building on areas that are at increased risk
Population expansion can increase the risk of a hazard
How are hazards percieved as advantageous to some people?
- some people make use of the fertile soils on floodplains or in the vicinity of a volcanoe can be considered a risk worth taking and living with the threat is accepted
What are the effects of diasters on HDES ?
HDES effects tend to do little long term damage to the economy as there is enough wealth and potential for redevelopment to br able to rebuild infrastructure and supporting those directly affected
What are the effects of disasters on LDES?
LDES are more reliant on support and aid both in the immediate aftermath of an event and also in the long term
What are the local level responses to a disaster?
Saving possessions, and safeguarding property
What are the global responses to a disaster?
Co-ordination rescue and humanitarian aid
The intensity and magnitude if the event as well as the original state of the infrastructure affects the spread of international response
What is the automatic disaster analysis and mapping system (ADAM)?
A database that pools informarion from the US geographical society, world bank and world food programme
It allows almost immediate access to such information as the scale of the disaster and what supplies are avaliablly localy
What is fatalism?
Fatalism = acceptance - a view that nothing can be done to mitigate the hazard and therefore the outcome and the loss will be inevitable
What is community prepareness/risk sharing?
Prearranged measures aimed at reducing the loss of life and property damage
Can be done throigh public education and awareness programmes, evacuation procedures and provison of the neccesary resucres before hazards occur
Prediction
The ability to give warnings so that action can be taken to reduce the impact of hazardous events
E.g. remote sensing and seismic monitoring, advances in communications and warnings communication promptly
Preparation
Prearranfed measures that aim to reduce teh loss of life and damage to property throuhh increased awareness
E.g. Buildings/infrasturtucre made to withstand gazards
Prevention
Trying to stop the natural hazard occurring at all (impossible)
Mitigation
Physical action that takes place to lessen the impact of a natural hazard
Adaptation
Changing behaviour or physical/natural environment to reduce the risk
What is hazard management cycle ?
Hazard management cycle = shows phases of response, recovery, mitigation and prepardness in the management of a hazard
- Shown as a 4 stage continuous model
- Each stage is linked to the next but will also be an overlap between the stages
- Cycle involves key players/stakeholders: the government (at all levels) international organisations (The UN, Aid agencies) Business and Community
Recovery
- In short term how can affected area regain its essential services to aid long term recovery - restoration of services so that longer term planning and reconstruction can begin
- In the long term how will impacted area return to normal
Response
- Speed will depend on the effectiveness of emergency resposne teams and level of prepardness
- Short term responses focus on saving lives
- Assesment of damage will determine level of recovery required
prevention & mitigation
- How can impact of an event be lessend e.g. retrofitting or firebreaks in area ro prove to wildfires
- Will they be short term /
- long term protection of natural barriers such as coral reefs which protect the shore against storm surges, support after disaster in form of aid and insurance and reduce long term impacts
- Will they be hard or soft engineered?
- How much aid assistance comes from overseas
- Communities may not be avaliable in all high risk areas even in HDES and not at all in LDES who need it the most
preparation
- Is the community ready for the next hazard ( education)
- Good preparation allows for a more effective response to another event
- High risk areas tend to be better prepared
What is parks repsonse model ?
Parks response model = shows the changing quality of life through different phases of a disaster
*steepness of downward curve during disruption depends on the nature of the event (volcanoes could have weeks of warning so be able to mitigate the impacts)
What is a multi hazard zone?
Multi hazard zone = an area which is prone to a range of hazards. Some of these may be interrelated such as earthquakes triggering a landslide
What is Deggs model?
Deggs model shows the relationship between vulnerability, hazards and disaster. He indicates the interconnectedness between physical and human factors of place (synopicity and varying rates of different players / stakeholders)
Vulnerability includes: population? Devloped?What is the land used for? Emegency services prepared?Infrastructure?
Natural Hazard : When did it last occur? How large was affected area? How long did it last? How big was the event? etc
What are root causes?
Root causes = human context of place. This affects the vulnerability of the population
High inequality will rate low on hdi <0.555- peoples needs are not being met
Means either higher chance of people being killed or higher chance of people being rescued
Resillence
Resilience = the ability of a system, community or society exposed to hazards to resist, absorb and accommodate to and recover from the effect of a hazard
Relief
Stage 1 - Relief
(hours-days)
● Immediate local
response - medical
aid, search and rescue
● Immediate appeal for
foreign aid - the
beginnings of global
response
Reeconstruction
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
Rehabilitation
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.
Risk sharing
Risk sharing = working together to reduce the risk and sharing the cost of hazard response
How many people died in haiti eq 2010?
200,000 people
Deaths were due to infrastructure collapses not the eq itself
Primary hazard
Primary hazard = happen immediatley and are caused by the energy released by the earth
Secondary hazard
Secondary hazards = happen as a result of the primary hazards
What is sea floor spreading?
Sea-floor spreading = Movement of oceanic crustal plates away from constructive plate margins
Who produced the idea of sea floor spreading and when?
-Harry Hess in 1962 and this helped support wegeners theory of continental drift
-Hess discovered that rocks increased in age with distance from mid ocean ridges and that new oceanic crust were therefore being formed when plates diverged
- Hess theory was backed by the magnetic dating of these rocks (paleomagnetism)
-
Facts about sea floor spreading?
- 12,000ft long mountain range formed as mid alantic ridge a ridge of underwater volcanoes
-Molten rock pushed up from inside earth at the ridge new crust new ocean floor - Rate of spreading is expected to be up to 5cm per year
What is paleomagnetism?
Paleomagnetism = Measurement of the magnetism preserved in older rocks
Facts about paleomagnetism?
-Approximatley every 400,000 years the earths magnetic field swtitch polarity between north and south
-Studies in 1960s of magnite ( iron oxide) produced from the balsatic lava along mid ocean ridge records the earths magentic orientation at that time
-Both age and magnetic orientation and symetrical suggesting that the oceanic crust is slowly spreading away from this boundary and therefore supporrs theory of contineyal drift
-
What is mantle convention?
Mantle convention = the rising and falling of magma within the asthenosphere
Facts about the asthenosphere
part of the mantle that lies directly beneath the lithosphere
Gravitational sliding
Gravitational sliding = the movement of tectonic plates as a result of gravity at mid-ocean ridges and deep sea trenches (ridge push and slab pull)
Ridge push
Ridge push = the higher elevation at an ocean ridge causes gravity to push down and drag crust away from the ridge
Slab pull
Slab pull = The process whereby , following subduction, the lithosphere sinks into the mantle under its own weight ‘pulling’ the rest of the plate with it
How does ridge push occur?
Ridge push is a result of gravitational forces acting on young oceanic lithosphere, causing it to slide down the asthenosphere and push on the lithospheric material further away from the ridges
Magma rises as the plates move apart. The magma cools to form new plate material. As it cools It becomes denser and slides down away from the ridge. This causes other plates to move away from each other.
How does slab pull occur?
Slab pull is a force that results from denser oceanic plates subducting beneath less dense continental plates. The gravitational force of the sinking oceanic plate drags the rest of the plate along with the portion experiencing slab pull
What are plate margins?
Plate margins = the place where two plates meet and the crust either side of this is the junction
What are constructive (divergent) plate margins?
Constructive plate margins = when two plates separate (diverge) and form a constructive margin
What are the two types of divergence?
mid - ocean ridges , rift valleys
How do mid ocean ridges form?
- Forms thousands of kilometres across the floor of submarine mountains
- Transform faults cut across the ridges, occurring at a right angle to the plate boundary, separating sections of the ridge
- Can rise up to 4000m above ocean floor
-Volcanic eruptions along ridges build
How are rift valleys formed?
- Formed when the lithosphere stretches causing it to fracture into sets of parallel faults
- The land between these faults then collapse into deep wide valleys that are separated by upright blocks of land called horsts
What are destructive (convergent) plate margins?
Destructive plate margins = when two plates collide they form a destructive plate margin
What are the three types of destructive plate margins?
- Oceanic meets continental
-Oceanic meets oceanic
-Continental meets continental
Oceanic meets contitnental?
- The meeting of two plates is associated with subduction
- Oceanic plate is denser than lighter contitnental plate so it subducts beneath it
- Exact point of collision is marked by bending of the oceanic plate to form a deep ocean trench (e.g. peru -chile trench)
- As two plates converge the contitnental land mass was uplifted, compressed, bucked and folded into **chains of fold mountains **
- Continuous compressing, simple folding can become assymetrical then overfolded making a **recumbent fold **
- Nappe can occur if increased compressing makes middle section thin
- Descending oceanic plate melts at depth beyond 100km and completley destroyed by 700km
- Friction may lead to stresses building up which may be released as **intermediate or deep focus earthquakes **
- Melted oceanic creates magma which rises in great plumes passing through cracks and faults
What is the zone of melting?
Benioff zone - caused by both increasing depth and friction
Oceanic plate meeting oceanic plate
- One plate (faster or denser) subducts beneath the other
- Leads to formation of a deep ocean trench and melting
- Rising magma from benioff zone forms crescents of submarine volcanoes along plate margins which may grow to form **island arcs **
Continental meets continetal
- Continental are of lower density than the athenosphere beneath them which results in no subduction occuring
- Colliding plates become uplifted and buckle to form** high fold mountains **
- No volcanic activity as there is no subduction but **shallow focus earthquakes **can be triggered
- Young fold mountains continually growing and compressing
What are conservative plate margins?
Conservative plate margins = where two plates slide past eachother causing earthquakes to occur
Two plates sliding **past **eachother
Conservative plate margin
- Crust is not destroyed or subducted
- No melting rock which results in no volcanic activity or formation of new crust
- Very active margins and associated with powerful earthquakes
- Friction between two moving plates leads to stresses building up wherever sticking occurs
- Stresses may be released as shallow focus earthquakes such as LA (1994), SF (1906, 1989)
Magma plumes
- Hotspots form around core if decay is concentrated
- Heat in lower mantle creates localised thermal currents where magma plumes rise vertically
Usually located at plate margins but can be risen within centre of plates and burn through lithosphere to create volcanic activity on the surface - Hotspots remain stationary, movement of overlaying plate results in formation of chain of active and extinct volcanoes as plate moves away
What is a hotspot?
What are transform faults?
The great african rift valley
An example of divergent plate boundary that occur in the middle of continents
May eventually form a new ocean as eastern africa splits away from the rest of the continent
What is the spatial distribution of volcanoes?
What are hot spots?
What is the VEI?
A volcani richer sacle used since 1992 using logarithmic scale from 0-8 volanic explosivity index
Compares size of volcanic eruption (magnitude) by measuring amount and height of matter ejcted and how long the eruption lasted
Shield volcano
Shallow-sided amd wide found at constructive plate margins and formed of balsaltic lava
Composite volcano
Steep-sided and tall found at destructive plate margins formed of andesitic and rhyolitic lava
Lava
Molten rock above the earths surface
Type of magma ? Characeristics? E.gs?
Hawaiian Volcanoes
- Type of magma: basaltic
- Characteristics: Active, lava flows gently from central vent
- E.g.: Kilauea, Hawaii
Type of magma ? Characeristics? E.gs?
Strombolian volcanoes
- Type of magma: Thicker basaltic
- Characteristics: Frequent explosive eruptions of tephra and steam and occasional short lava flows
- E.g.: Mount Etna, sicily
Type of magma ? Characeristics? E.gs?
Pillian volcanoes
- Type of magma: Rhyolotic
- Characteristics: Exceptionally violent eruptions of gases, ash and pumice, torrential rain storms cause devestating lahars
- E.g.: Moount vesuvis italy
Type of magma ? Characeristics? E.gs?
Icelandic volcanoes
- Type of magma: Baslatic
- Characteristics: Lava flows gently from fissures
Type of magma ? Characeristics? E.gs?
Vulcanian volcanoes
- Type of magam: Baslatic, desitic and rhyolitic
- Characteristics: Less frequent but more violent eruptions of gases ash and tephra
Type of magma ? Characeristics? E.gs?
Vesuvivian volcanoes
- Type of magma: basaltic andestic and rhyolitic
- Characteristics: following long periods of inactivity very violent gas explosions blast ash high into the sky
Type of magma ? Characeristics? E.gs?
Peleean volcanoes
- Type: Andesitic and rhyolitic
- Characteristics: Very violent eruptionsof nuees ardneees
What are primary effects?
- Tephra
- Prycolastic flows
- Lava flows
- Volcanic gases
Tephra
Solid material of varying grain size ranging from volcanic bombs to ash all ejected into the atmosphere
* Larger the particle shorter distance of travel from source
* Volcanic bombs are very dangerous people tend to avoid them
* Fine ash can be thrown into atmosphere and strong winds blows it around the earth reducing incoming radiation and cooling the earth
Pyroclastic flows ( nuees ardentes)
Very hot (over 800 degrees gas charged high velocity flows made up of a misture of gas and tephra
Hug ground and flow down sides of volcanoes up to 700km p/h
- in 2018 flows from volcan de fuego guatemealakilled as many as2900 peopleand destroyed on estimated8500 hectares of agriculture land
Lava flows
- lava can flow quickly or slowly depending on its viscosity.
- Silica makes lava viscous and slow, which is common in explosive eruptions.
- Rarely cause injury to people due to their relativley low velocity
- ## Often unstoppable so damage crops, buildings and block roads
Volcanic gases
- released during some eruptions, even CO₂ can be toxic as it can replace oxygen as it is heavier
- Carbon dioxide, carbon monoxide, hydrogen sulphide, sulphur dioxide and chlorine
- In 1986 co2 from lake in the crater of nyos camerons killed..
Secondary effects (natural ) (volcanoes)
- Lahars
- Flooding
- Volcanic landslides
- Tsunamis
- Acid rain
- Climate change
Lahars
Lahars = unconsolidated ash from recent eruptions combined with water may be swept down river valleys in the form of hot, dense, fast moving mud flow
* Water can come from heavy rain e.g. mount pinatubo, phillippines in 1991
* Melting snow and ice e.g. nevada del ruiz columbia 1985 completley destroyed the town of armeno 28,000 survived
Flooding
Flooding = when an eruption melts glaciers and ice caps
E.g. iceland in 1996 grimsvton
Volcanic landslides
Volcanic landslides = range in size from less than 1km3 to more than 100km 3
* High velocity and great momentum of landslides allows them to cross between valleys and run up slopes several metres high
* E.g. the landslide at mount st helens in 1980 had a volume o 2.5km reached speeds of 50-80 m/s and surged up over a 400m high ridge located 5km from volcano
Tsunamis
Tsunamis = sea waves generated by violent volcanic eruptions such as those formed after the eruption of Krakatoa (indonesia) in 1883. This tsunami killed 36,000 people
Acid rain
Acid rain = volcanoes emit gases which include sulphur. When this combines with atmospheric moisture acid rain forms
Climate change
Climate change = the ejecetion of huge amounts of volcanic debris into the atmosphere can reduce global temperatures and is believed to have been an agent in past climate change
What is the top of tha arrow?
- Return to normality
- Improved qol
- “Build Back Better” e.g. in 2011 tsunamis in japan walls are now higher than previously
Short term responses
Short term responses (saving lives)
* Depends on magnitude and vulnerability of the population
* Priority of saving lives
* Evacuation
* Deploying emergency servives to provide first response treatment
* Some international aid may be given
Long term responses
Long term responses (preserving lives)
* Involves long term planning in future preparedness, mitigation, prevention and adaptation
* Introduction of volcanic monitoring, hazard mapping, evacuation plans to prevent future loss of life
* Stockpiling of food and water supplies for future use
Preparation ( volcanic eruption)
- Monitoring and prediction allows time for evacuation (people fear losing farmland and homes e.g. pinatubo)
- In iceland this is done by icelandic meterological office
- Training of emergency services
- Observation stations e.g. Monserrat
Iceland:
* Vistors encouraged to download 112 app which send text messages should and eruption be imminent
* Hekla in particular is closley monitored as it is underneath the flight path
Mititgation ( Volcanic eruption)
- Aid (domestic or from overseas)
- Monitoring to predict future eruptions
- Creating alert systems (sirens, speakers and social media) to warn public of threat alert (e.g. New Zealand)
- Evacuation camps for displaced people
- Stockpiling of emergency food and water supplies
- Diverting lava flows by digging trenches. dropping blocks into lava and using explosives e.g. etna or hawaiia
Prevention (stopping completely)
- Is this possible
- Advantages of volcanic events such as the Ash is a nutrious fertiliser for crops
Adaptation ( changing or adopting behaviour )
- Hazard mapping, exclusion zones, land use zoning to show high risk areas from Lahars and Lava flows
- Using ash for building materials
What is relief Parks model?
Relief is the immediate local and possibly global response in the form of aid, expertise and search and rescue
Rehabilitation
A longer phase lasting weeks or months, when infrastructure and services are restored, albiet possibly temporarily to allow the reconstruction phase to begin as soon as possible
Reconstruction
Restoring to the same, ot better, quality of life as before the evet took place. This is likely to include measures to mitigate against a similar level of disruption if the event occurs again
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Benefits and drawbacks of Parks model of human response to hazards?
- Could be considered better than HMC as it is time-linked
- Developed and devloping countries can easily be compared - one takes longer to recover than the other
- Multi-hazard zone may never reach normality if the rehabilitation stage takes a long time
Examples of root causes
Low access to resources, Limited influence in decision making, Poor governance and weak economic system
Examples of dynamic pressures
Lack of education,training and investment, Rapid population change and urbanisation
Examples of unsafe conditions
Poor construction standards, unsafe infrastructure, poverty, lack of social saftey net
Lithosphere
The layer of earth consisting of the rigid crust and upper section of the mantle
Athenosphere
The part of the mantle which lies directly beneat the lithosphere made of molten and semi molten rocks
Key facts about structure of earth
- Helps to understand why tectonic hazards occur
- Theory of plate tectinics has revolutionised
- Earths outershell is the curst and thickness between 5 and 10km beneat the oceans to nearly 70km under the continents
- Rocks in upper mantle are solid anf sit on top of athenosphere, softer almost plastic like rock which moves very slowly
- As earth rotates liquid outercore spills, earths magenetic field
- Cores internal heat is major cause fo earths tectonic activity
- Some heat may primeval - retained from the ball of dust and gas from which the earth evolved
- Earths greatest source of heat energy is from radioactivedecay (natural radioactive decay from euranium, thorium, potassium and other elements provides a continoous buy slowly diminishing heat
- Heat at core generates convection currents within mantle
oceanic crust
An occasionally broken layer of balsaltic rocks known as sima ( made up of silicia and magenesium)
continental crust
Bodies of mainly granictic rocks known as sial (silia and alumnumin)
core
The core is the centre and hottest part of the earth - reaches up to 6000 degrees celcius and is mostly made up of iron and nickel and is 4x more dense than the crust
inner core
inner core = solid and made up of iron nickel alloy
outer core
outercore = semiliquid and is mainly iron
Krakatoa (indonesia) in 1883.
Krakatoa (indonesia) in 1883. This tsunami killed 36,000 people
Andestic lava
Andestic lava has high viscosity and is more runny with a high silica content and more disolved gases and is more likley to explode when reaches surface
Basaltic lava
Baslatic lava has low silicia content and relativley fluid because of its low viscosity
Rhyolitic lava
Rhyolitic lava is a type of volcanic rock that is high in silica content, typically greater than 70%
* It has a very thick and viscous consistency, which influences how it flows and erupts1.
* Rhyolitic lavas tend to form thick blocky lava flows or steep-sided piles of lava called lava domes23.
* They erupt explosively, often producing abundant ash and pumic
Short term responses
Short term responses to volcanic acitivities ( saving lives)
- Depends on magnitude and vulnerability of population
- Priority of saving lives
- Evacuation
- Deploying emergency services to provide first response treatment
- Some international aid to be given
Long term responses ( preserving lives
- Involves long-term planning in future preparedness, mitigation, prevention and adaptation
- Introduction of volcanic monitoring, hazard mapping, evacuation, plans to prevent future loss of life
- Stock piling of food and water supplies for future use
Preparation (state of readiness of a volcanic eruption)
- Monitoring and prediction allows time for evacuation (jhowever, people fear losing their farmland and homes e.g. Mount pinatubo) (icelandic meterological office)
- Training of emergency services
- Observation stations e.g. monsterrat
- People monitor increase in release of various gases, Rise in level of lava lakes in volcanic crarers, Bulging upwards of surrounding land due to pressure below, increasing numver of relativley small eqs caused by rising magma, study of previous volcanic eruptions
Iceland:
Encourages tourits to download 112 app which send text messages should an eruption be imminent
Hekla is closley monitored as it is undernetah flight path those will have 15-30 warning time
Mitigation of volcanic hazards
- Risk assesments carried out by governments in countries at risk of volcanic hazards (phillipines) and produce series of alert levels to warn the public
- Once viscious lava has staryed to flow it can be possible to divert it from built eruption e.g. in Mt etna in sicility digging trenches, droppungf blocks into lava stream and using explosives slows down flow, diverting it
- 1973 haeimaey iceland poured sea water on front of lava flow to solidify it before it cut off their fishing port
- Hawaiian islands have built barries across valleys to protect settlements from lava flow and lahars
- Evacuation, exlusion zones (monserrat)
Prevention
Not possible to prevent eruption but can be reduced by mitigationb
evacuation
Benefits of living in proximity of eruption
Adaptation
- Hazard mapping, exclusion zones and land use zoning to show high risk areas from lahars and lava flows e.g. monserrat
- Using ash for building materials
