Tectonics Flashcards
Why not all tectonic activity is hazardous?
- low magnitude earthquakes
-volcanic eruptions vary in terms of their explosivity due to location and lava type - good building design limits collapses
- lack of population to be affected
-high frequency of events allows people to prepare and respond avoiding death and minimising damage
-accurate prediction allows efficient evacuation
PAR model
Shows a clear link between level of economic development in the root causes, leading to a progression of vulnerability,which then factors into hazard risk
How can hazard profiles aid effective management
-magnitude: most import factor in determining the success of modifying the event management strategies as most approaches cannot cope with Mega earthquake
-areal extent:vital factor as it determines the number of people affected but also the larger the are the more difficult it is for the existing emergency services to reduce loss of the earthquake event
-frequency:key factors in determining success of management as the more frequent the earthquake the more Likely the community is to be educated and aware of the hazard threat. Equally, low frequency can reduce the awareness of the hazard risk
- economic development:vital factor as it determines whether area can afford to implement all 3 types of strategies
Level of economic development
It refers to the broad socioeconomic status of a country: whether they recognise the hazard and have sufficient financial status to implement changes on national or local scales
Governance
The ability of an organisation/ group of people to plan or manage hazard events effectively.
Eg national government might finance emergency care, mandate education strategies or establish building regulations .
Local government night organise evacuation strategies.
Global governance might coordinate a tsunami warning system
What does level of economic development affect?
- available capital
-availability of resources
-level of expertise and specialist equipment
-quality of building design - quality of community preparedness -drills,education programmes
-likelihood of insurance coverage - reliance on international assistance
What does governance relates to
- ability to manage hazards
- strength of regulations on building design
-levels of corruption, so resource/capital availability
-organisation of drills and evaluation strategies
What does the disaster risk- poverty nexus model seeks to establish
-poverty is both a cause and consequence of disaster impacts
-that repaired occurrence helps to sustain and maintain poverty in a region
Global interdependence
Relates to how interconnected places are
Japan 2011 case study
- caused by the 9 magnitude earthquake that was caused by the build up in strain energy as the pacific plate sub-ducted under the Eurasian plate
- deaths, injuries,missing people, destroyed buildings
- repairing the motorway, better and improved warning and monitoring systems where put in place
-countries sent rescue teams, displacing people
Sumatra tsunami case study
-earthquake caused the tsunami
-killed people in 14 different countries,people made homeless,destroyed houses,caused diseases such as cholera
-took months to clean the debris, tsunami early warning systems put in place
Prediction
Knowing when and where a natural hazard will strike on a spatial and temporal scale that can be acted on meaningfully
Forecasting
Less precise and provides percentage chances of hazards occurring in a particular place
Hazard management cycle
It consists of the steps that emergency managers take in planning for and responding to disasters
-preparedness strategies:focus on ensuring that emergency services and people at risk are aware of how to react during an event.Following the event the response section of the hazard cycle is focused on the immediate needs of the population eg such as protection of life and property.This includes emergency medical response,evacuation and transportation,decontamination and the provision of food, water and shelter
-recovery is equivalent to long term responses and is where the city authorities focus on clean up and rebuilding
-mitigation involves authorities looking at the impacts of the hazard and rebuilding in a better way to reduce similar impacts from a future hazard
Park model
Stage 1: occurs prior to the event and shows that quality of life is at its normal equilibrium level
Stage 2:where the hazard occurs and again at this point quality of life is normal
Stage 3: where the event has happened and search and rescue is underway. Quality of life drops at this stage and is low for several hours up to servals days depending on the severity of the hazard and the level of development of the country
Stage 4:where relief strategies are underway and there is an organised programme of help. Quality of life improves at this time
Stage 5: refers to long term human response such as rebuilding and restoring normality. Quality of life returns to normal and In some cases can be higher than it was originally
Mitigation
Is using technology to remove the cause
Adaptation
Working around the effect of a hazard
Modify the loss
- emergency aid
Modify the loss
- emergency aid: long or short then but can make the country dependent
-insurance:some may rely on insurance to recover losses
Modify the vulnerability
-hi tech monitoring m: international stateliness and aircraft monitor changes in the earth
-prediction: observing changes in volcanic shapes or low magnitude earthquakes could suggest whether a disaster is likely
- education: teaching communities about hazards and protection enables the community to gain strength and withstand a shock better
-community preparedness:earthquake drills and alarms prepare communities for how to best protect themselves in a disaster
Relationship between seismic activity and plate boundaries
- strong relationship
- earthquakes occur on all plate boundaries
-most frequent on convergent( destructive and collision) boundaries
-highest magnitude (>9 on the Ritchter scale ) occur on destructive boundaries
-significant amount of intraplate activity as a result of :volcanic activity at mantle plumes,faulting in fold mountains, human activity
Relationship between volcanic activity and plate boundaries
-very strong relationship
-approximately 90% of active volcanoes occur around the pacific ring of fire( largely destructive plate )
-most explosive volcanos(stratovolcanos, composite volcanos) associated with destructive plate boundaries
- shield and fissure volcanos are associated with constructive boundaries
Fissure volcano
-very liquid lava which is emitted from fractures and flows widespread
-basaltic magma
-effusive eruption(Icelandic or Hawaiian )
Shield volcano
-large
- sometimes has a collapse caldera
-basaltic magma
- liquid lava emitted from a central vent
-associated with construction plate boundary/mantle plumes
Composite volcano
- large
- more viscous lava
- destructive plate margin
- explosive ( pyroclastic debris
-andesitic magma - emitted from a central vent
Caldera volcano
-destructive plate margin
-opinion eruption
-Associated with plug domes
- andesitic magma
-very large composite volcano collapsed after an explosive period
Factors affecting risk
-level of vulnerability of a population
-probability of a hazard of a given magnitude occurring
Factors affecting vulnerability
-level of perceived risk
-social variables within a country eg affluence
-level of economic development
-nature of a hazard: Hazard profile
Degg disaster model
Shows that in order for a disaster to occur a hazard must interact with a vulnerable population
Actual risk
The probability of a hazard causing harmful consequences- it is a statistical measurement. Involves the relationship between the vulnerability of a population and the nature of a hazard as shown in the degg model
Perceived risk
An individuals or groups view of the risk. Affected by things such as awareness:education of hazards and the length of time singe the previous event
Vulnerability
The susceptibility of a community to a hazard or to the impacts of a hazard event
Natural hazard
A perceived natural event which has the potential to threaten both life and property
Disaster
The realisation of a hazard when it causes a significant impact on a vulnerable population
Resilience
The capacity of a given society to both withstand the impact of a hazard and recover from one
Degg disaster model
Model which shows that in order for a distaste to occur, a hazard must interact with a vulnerable population
Benioff zone
An area of seismic activity that corresponds with the slab being thrust downwards in a subduction zone
Subduction zone
Broad areas where two plates are moving together often with the thinner more dense oceanic plate descending beneath a continental plate
Slab pull
Where older,colder plates sink at subduction dined because as they cool they become more dense than the underlying mantle
Formation of a tsunami
Tsunami appears when water is displaced. The main cause is submarine earthquakes however they can be also cause by volcanic activity and landslides. If they are caused by seismic activity vertical movement of crust appears.This displaces the water column above. It produces waves with low amplitude and long wavelengths, radiating outwards.As it reaches the shoreline it produces a vacuum effect sucking all the water away revealing the coastline and the seabed.
The friction causes compression of the waves which then causes them to gain height. The run up is dependent on the topography of the seabed
P waves
Vibrations caused by compression. Spread quickly at 8km/sec
S waves
Vibrate at right angles to the directions of travel and cannot travel through liquids
4km/sex
L waves
Surface waves with vibrations occurring in the horizontal plain. Have high amplitude
What does volcanic explositovity measures
Volume of ejects
Duration
Height of the column
Continental drift -Alfred wegner
- rock type= limestone is formed in warm shallows seas that contain corals- it indicates tropical climates. If found in different places it indicates shift of continents
- fit of continents: supercontinent called Pangea 175 millions years ago all continents were joined together. No longer the case indicating that continents moved
- fossils= same type of fossils distributed over different continents. Eg glossopters are distributed across antarica,America, Australia and South America meaning that continents were once joined together
Sea floor spreading- Harry Hess
- mid ocean ridges=the invention of sonar allows to obtain a bathymetric profile which allows to revel the high heat flow at mid ocean ridge due to rising magma
-age of the ocean floor =rocks at the mid ocean ridge are the youngest and they get older as you move away from mid ocean ridge
-magnetic anomalies =Magnus symmetric about the ridge. Rocks are the same age and have the same polarity so they must have formed together but subsequently have been pushed apart
