Hazards Flashcards
Define a hazard
Something that is a potential threat to human life or property
What are the 3 types of natural hazards
Geophysical
Atmospheric
Hydrological
Define vulnerability
How susceptible a population is to the damage caused by a hazard
Define Magnitude/Intensity
How powerful the hazard is
What does the park model show
The different phases of response to a hazard
What is the asthenosphere
The upper mantle layer of the earth
Semi molten
What is ash
Fine particles and dust ejected during an eruption
what is continental crust
Crust that forms the continents of the lithosphere
Describe continental drift
Movement of tectonic plates due to varying weights of crust caused by slab pull
What is the epicentre
The point on the surface, directly above the earthquake
Define fatalism
The belief that hazards are uncontrollable, so losses should be accepted and mitigation is unnecessary
What is the focus
The place in the crust where the energy is released
What is a hotspot
Volcanoes found away from plate boundaries due to magma plumes close to the surface
What is a lahar
A flow of mud and debris
What is the lithosphere
The upper crust of the earth
Outline the process of liquification (4)
Sediment loses strength and stiffness as a response to a stress
Solid material behaves like a liquid
Requires a degree of saturation to occur
Can cause damage to infrastructure and cause buildings to collapse
Outline the concept of hazard management cycle
A continuous loop which explains the approach to managing a hazard
Preparedness is concerned with using evidence and data from previous events to plan for hazards
Good preparation minimises impacts from a hazard
Response ensures providing medical aid and services to save and help people
Outline the factors which lead to the formation of mudflows (4)
Rapid melting of ice and snow following a volcanic eruption
Can be caused by tropical storms following an eruption
Typically flow down a valley side and occupy river channels
Speed of the mudflow can be affected by steepness of slope/gravity
Outline the concept of mitigation in relation to the management of hazards
Mitigation is action to reduce the potential effects of a hazard
HMC includes mitigation as part of the pre-event action
This includes hazard mapping
Shows areas which are most vulnerable to a hazard
What are love waves
A surface wave with horizontal displacement
What are the four phases in the hazard management cycle
Mitigation
Preparedness
Response
Recovery
What are the 4 phases in the hazard management cycle for?
Mitigation - aims to minimise the effect of future hazards
Preparedness - planning how to respond to a hazard
Response - how people/services react to a hazard
Recovery - Aims to get the affected area back to normal
What are geophysical hazards
Caused by land processes such as earthquakes and volcanoes
What are atmospheric hazards
Caused by climatic processes such as tropical storms and droughts
What are hydrological hazards
Caused by water movement such as floods
What are the theories of how tectonic plates move
Convection currents, ridge push and slab pull
How do convection currents move tectonic plates
The core is very hot, lower parts of the asthenosphere heat up and slowly rise
As they move to the top of the asthenosphere they cool down and become more dense and slowly sink
The circular movement of the semi-molten rock create drag on the tectonic plates causing them to move
How does ridge push move tectonic plates
Heat from rising convection currents, causes upwelling between two plates
As new sea-floor cools it slides laterally down the slope due to gravity
This pushes the plates aside by ridge push
How does slab pull cause movement of tectonic plates
Pressure of plates moving as a result of ridge push forces 2 plates together
Loss of heat from the lithosphere over time causes it to become cold and dense enough to have negative buoyancy
This allows the plate to subduct under the less dense crust
This drags the surface plates downwards by slab pull
Describe sea floor spreading
As tectonic plates diverge, magma rises up to fill in the gap created this then cools to form new crust
Overtime the new crust is dragged apart to form more new crust
When this happens at a plate margin under the sea, the plate margin gets wider
What are the three types of plate boundaries
Constructive
Destructive
Conservative
On what type of plate boundaries do volcanoes form on
Constructive and destructive
How do volcanoes form on constructive plate boundaries
When two plates are moving apart, the mantle is under pressure from the plates above
When they move apart the pressure is released at the margin
The release causes the mantle to melt producing magma, the less dense magma rises and erupts to form a volcano
Example of constructive plate boundaries
Iceland
Mid-Atlantic ridge
African rift valley
How is magma formed at constructive boundaries
Asthenosphere rises, pressure decreases towards crust so rock melts
Plates moving apart creates a gap that relieves pressure
