Hazards

• What is a natural hazard?


  A natural hazard is an event that threatens both life and property
• What are the different types of natural hazards?


  - geophysical

  - atmospheric

  - hydrological
• What is a geophysical hazard?


  caused by the movement of tectonic plates
• What is an atmospheric hazard?


  created by the process occurring in our atmosphere
• What is a hydrological hazard?


  created by water bodies, mainly the ocean
• What is hazard perception?


  the way in which someone understands or interprets a hazard
• What is fatalism?


  acceptance, a view that nothing can be done to mitigate the hazard and therefore the outcome, loss will be inevitable
• How can the hazard management cycle help us to understand natural hazards?


  - the hazard management cycle is a model shown as a 4-stage continuous cycle

  - each stage is linked to the next, but there will also be overlap between the stages

  - the cycle involves key players/ stakeholders: the government, international organisations, businesses and community groups
• What is the hazard management cycle?


  shows phases of response, recovery, mitigation and preparedness in the management of a hazard

  
• Recovery (Hazard management cycle)


  - in the short-term, how can the affected area regain its essential services to aid long term recovery

  - in the long-term, how will the impacted area return to 'normal
• Response (Hazard management cycle)


  - speed will depend of the effectiveness of emergency response teams and level of preparedness

  - short term response will focus on saving lives

  - assessment of damage will determine level of recovery required
• Prevention and mitigation (Hazard management cycle)


  - how can the impact of an event be lessened

  - will these be short to long - term options, hard engineered or soft?

  - how much aid assistance will come from over seas?

  - will communities be insured even in HICs?
• Preparation (Hazard management cycle)


  - 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
• Park's response model


  shows the changing quality of life through different phases of a disaster

  
• What is a multi hazard zone?


  an area which is prone to a range of hazards, some of these may be interrelated, such as earthquake triggering landslide
• How does Degg's model help to explain the importance of vulnerability?


  Dr Martin Degg believes that a hazard becomes a disaster when a vunerable population cannot cope using its own resources, he has shown this concept in a 'disaster model', the greater the scale of the natural hazards and the more vulnerable the population , the greater the disaster will be
• What are the venerability factors?


  - economic status

  - education

  - resources

  - previous experiences

  - fatalism

  - infastructure

  - age

  - gender
• What is the lithosphere?

  a layer of crust and solid upper-most mantle
• What is the astenosphere?


  the upper layer of the earth's mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection is thought to occur
• What are the two types of crust?

  oceanic and continental
• Oceanic crust characteristics


  - 60% of the earth's surface

  - basaltic and sima

  - created by lava from mid ocean ridges

  - constantly being created and destroyed

  - more dense than continental crust

  - 200 million years old

  - 6-10km
• Continental crust characteristics


  - 40% of the earth's surface

  -30-70km

  - less dense

  - over 1500 million years old

  - sial and granilic

  - neither created or destroyed

  - forms the land masses
• What is the plate tectonics theory?

  a theory developed more than 60 years ago to explain the large scale movements of the lithosphere, it was based around the evidence of sea-floor spreading and ocean topography and palaeomagnetism
• What is sea floor spreading?


  the formation of new areas of oceanic crust, which occurs through the upwelling of magma at midocean ridges and its subsequent outward movement on either side

  
• What is palaeomagnetism?


  the study of past changes in the earth's magnetic field
• What is gravitational sliding?


  the movement of tectonic plates as a result of gravity
• What is ridge push?


  high elevation at mid-ocean ridges

  gravity causes elevated lithosphere to push on lithosphere far from ridge axis, causing lithosphere to move away from ridge axis
• What is slab pull?


  the processes whereby, following subduction, the lithosphere sinks into the ma the under its own weight, 'pulling' the rest of the plate with it

  
• What is a plate margin?


  the place where two plates meet and the crust either side of this junction
• What are the different types of plate margins?


  there are three main types of plate margins

  - constructive

  - destructive

  - conservative
• What is a constructive plate margin?


  where two plates are moving away from each other

  - between two oceanic plates creates a mid-ocean ridge and transform faults

  - between two continental plates creates a rift valley
• What is a destructive plate margin?


  where two plates are moving towards each other

  -between an oceanic and continental plate and associated with subduction

  - between two oceanic plates, creating island arcs

  - between two continental plates, known as a collision zone
• What is a conservative plate margin?


  where two plates slide past each other causing earthquakes to occur
• What is magma?


  molten rock beneath the earth's surface
• What are magma plumes?

  a rising column of hot rock found at a plate margin or in the middle of a plate (also known as a hotspot)
• Where are magma plumes found?


  - the vast majority of volcanic eruptions occur near plate margins

  - magma plumes are found where localised thermal currents are created by radioactive decay, these plumes 'burn' through the lithosphere, creating volcanic activity on the surface

  - magma plumes are stationary but the plate on top of which they are found is in motion, thereby forming a chain of volcanoes with the most extinct volcano furthest from the magma plume
• What is a hotspot?

  an intraplate volcano caused by a magma plume
• What is the spatial distribution of volcanoes?


  the relationship between volcanoes and tectonic plate margins is clear, the 'pacific ring of fire' shows particularly high densities of volcanoes stretching from the Aleutian Islands, through Japan, the Phillipenes and across to New Zealand
• What does VEI stand for?

  volcanic explosive index
• What is the volcanic explosivity index?

  - the "volcanic Richter scale" used since 1982

  - used to describe and compare the size of volcanic eruptions (magnitude) by measuring the amount and height of volcanic matter ejected (tephra and ash fall) and how long it lasts

  - scale from 0 to 8

  - a super volcano= 8

  - logarithmic