Hazards (general knowledge and volcanoes) Flashcards
define hazard
a natural hazard is a threat which has potential to cause injury, loss of life, damage to property or socio-economic disruption. a hazard can be categorised as a geophysical hazard, atmospheric hazard or hydrological hazard. hazards may develop into a disaster if it poses great damage or loss of life.
describe the acceptance perception to hazards?
-acceptance includes fatalistic tendencies. the perception relates to the viewpoint that hazards are natural events or result from an “act of God” and subsequently are uncontrollable through human action. the fatalistic response to hazards often results in substantial loss of life due to their limited organisational capacity. the culture in the country is crucial in determining the perception to hazards: with traditional religious countries typically following the acceptance perception in comparison to westernised secular societies.
describe the adaption perception to hazards?
adaption follows the viewpoint that natural hazards will occur, influenced by both natural and anthropogenic factors. however, there is a need to adjust systems, respond flexibly and research new technology which will aim to mitigate the hazard
describe the domination perception to hazards?
domination follows the viewpoint that hazards are extreme events which are predictable through scientific research, engineering and monitoring technology. hazard perception in developing countries is typically centred around domination due to the available money, technology and skilled personnel that enables them to predicts the hazards occurrence in order to prepare for their impact.
outline the different phases of the Park Model
-the Park Model aims to show the effects of a hazard on the quality of life over a sequence of time
-stage one is pre-disaster which displays the quality of life prior to the event is at its normal equilibrium level
-stage 2 is disruption which is during and directly following the hazard event occurring in which there is destruction of property and loss of life.
-stage 3 is relief which presents in the aftermath of the event search and rescue efforts are underway. the quality of life significantly drops and remains low for several hours up to several days.
-stage 4 is rehabilitation which involves an organised programme of help to resolve longer-term problems such as providing temporary shelters
-stage 5 is reconstruction which involves rebuilding infrastructure in order to return the quality of life back to normality or occasionally to a higher standard due to improvements to infrastructure.
outline the stages of the hazard management cycle
-preparedness involves strategies focussed on ensuring that emergency services and civilians are aware of responses to the hazard which can involve educating people on evacuation procedures
-response is focussed on the immediate needs of the population once the disaster has occurred including emergency medical response or evacuation from the danger zone
-recovery is equivalent to long-term responses to the hazard which involves authorities reestablishing normality through repairing and rebuilding houses.
-mitigation involves observing the impacts of a hazard and rebuilding in an improved way to aim to minimise the impacts of future hazards
describe the earths internal structure
-the earth is composed of three main sections: the core, the mantle, and the crust
-at the centre of the earth lies the core which is split into the inner core and outer core. the inner core is solid consisting of iron and nickel whilst the outer core is composed of liquid iron and nickel
-the mantle is the thickest layer, being approximately 2,800 km thick. it is comprise of molten and semi-molten rocks with lighter elements of silicon and oxygen. the asthenosphere which lies beneath the lithosphere is semi-molten
-the crust is the thinnest layer forming the outer shell of the earth. there are two types of crust: continental and oceanic. the continental crust is 30 to 70 km thick but is composed of less dense material than the oceanic crust which is 6 to 10 km thick.
describe constructive plate margins
-when two plates separate/diverge they form a constructive margin
-ocean ridges are formed upon the plates diverging . the space between the plates is filled with basaltic lava upwelling from the asthenosphere, which solidifies to form a ridge. transform faults are regular breaks across the ridges forms at right angles to the plate margin
-when plates separate on continental areas the crust fractures into sets of parallel faults. the areas of crust between these faults collapses into deep, wide valleys that are separated by upright blocks of land called horsts
describe destructive plate margins
-when two plates collide/converge they from a destructive margin
- where a continental plate and oceanic plate converge, the oceanic plate is subducted beneath the continental plate due to its higher density. the downwarding of the oceanic plate forms a very deep section of the ocean called a oceanic trench.
-when two oceanic plates collide the denser of the two plates is subducted beneath the other, during subduction the descending plate is subjected to high temperatures and pressure which melts to plate into magma. the magma is less dense than the surrounding asthenosphere therefore rises towards the surface emerging as explosive composite volcanoes. the eruptions take place offshore thus a line of volcanic islands form called island arcs.
-when two continental plates collide neither are subducted due to equally low densities. the plates colliding causes the plates to crumple upwards to produce fold mountains.
describe conservative plate margins
-conservative plate margins occur when two plates are sliding past each other either in the same direction at different speeds or in opposite directions. the two plates get locked together in places causing pressure to build up. this causes the plate to jerk past each other, releasing the energy as an earthquake. these are typically shallow focus earthquakes due to the absence of subduction subsequently high magnitude earthquakes.
describe magma plumes
-ninety five percent of volcanic activity occurs close to tectonic plate margins with the remainder occuring in intraplate locations associated with magma plume activity
-radioactive decay within the earth’s core generates very hot temperatures.
-if the decay is concentrated then hot spots form, heating the lower mantle by creating localised thermal currents where magma plumes rise
-these plumes occasionally burn through the lithosphere to create volcanic activity on the surface
describe the effect of pyroclastic flows
-a pyroclastic flow composed of hot rocks, ash and volcanic gases can travel down the flanks of a volcano at speeds of up to 200 metres per second with temperatures of up to 1000 degrees celsius.
-they pose as one of the deadliest volcanic hazards due to widespread loss of life and destruction caused by burning and burial under debris
describe the effect of lava flows
-flows of lava can be released from a volcanic vent down the sides of the volcano
-shield volcanoes tend to release low-viscosity basaltic lava which has the ability to flow 10km/h down a steep slope
-lava flows are typically slow allowing people to have time to evacuate the affected areas.
describe the effect of lahars
melted snow and ice stemming from the eruption combine with volcanic ash and rocks it forms fast flowing mud flows known as lahars which rush down the flanks of the volcano at speeds of 200 km per hour
describe the effect of volcanic gases
-volcanoes eject large quantities of volcanic gases including carbon dioxide and sulphur dioxide. if inspired by humans these gases can contribute to breathing difficulties.
-the sulphuric acid in the atmosphere reacts with rainwater to form a weak sulphuric acid. once it precipitates as acid rain it contributes to ecosystem damage and deterioration of stone and metal
