Hazards Flashcards
What is a hazard
A source or situation with potential to cause harm in terms of human injury, ill-health, damage to property, the environment or a combination of these
Landforms
Young fold mountains
They form when 2 plates meet, due to them being the same density neither plate subducts. This then causes both plates to buckle due and the ancient oceanic plate is subducted slightly due the large amount of pressure but there is no subduction of the continental plate. This means continental crust piles up on the lithosphere due to the pressure and the young-fold mountains are that continental crust. e.g Himalayas
Hot spots
Hot magma plumes from the mantle rise and burn through weaker parts of the crust. Magma plumbs are thought to be the driving effect of convention currents.
Magma from the core rises as a shield volcano, breaking through the sea and creating new land.
How hotspots cause island chains
Formation of a magma plume/ hot spot. Due to constant plate movement and the direction of this, the crust is moved from over the magma plume, therefore creating an inactive volcano which erodes down over time. The new crust that goes over the magma plume then under goes the same process of the lava seeping through creating another island, due to the rotation of the plates this movement is usually curved and creates island arcs. EG Hawaii
Rift valley
The lithosphere is extended ( pulled apart ) as the 2 parts of the crust move apart a central block drops in the gap formed, this block will then drop further due to the crust being further extended and fractured. Over time the boundaries of this block also drop and cause this process to happen again to those boundaries and land can collapse creating a rift valley EG the Somali Ethiopia valley - at constructive plate boundary
Mid oceanic ridge
Form at constructive plate boundaries. Where oceanic plates move apart after a collision, magma rises through the gap and creates new land and a mid oceanic ridge. The ridge can be pushed upwards by water or more magma- when the ridge gets higher it is pulled down by gravity and the ridge pushes down.
Deep sea trenches
Plates meet a continental plate at a destructive plate boundary, the oceanic plate is subducted under the continental plate due to the density difference and the process of slab pull. The slab of plate is pulled away causing more subduction and the seafloor bends to create a U shaped trench-slab pull. EG the Mariana Trench
Human responses and diagrams to show it ( HMC and park model )
Hazard management cycle
A 4 stage cycle built up of the hazard, response, recovery, mitigation and preparation
Response section
These are the short term responses which as search and rescue. Their main sims are to try and save lives and protect property
Recovery section.
These are the long term responses such as the rebuilding stage and the clean up of the damage caused by the hazard
Mitigation/preparing section
The 3 B, build back better. This is the period of preparing for the next event and trying to limit the damages. One way of doing this is educating people and improving infrastructure such as flood walls or earthquake resistance buildings
Pros
Pros :
- there is emphasis on the before stage which can reduce loss once the hazard occurs
- helps asses how good previous hazard management was
- reduces stress in the people as they are assured that management is taking place to reduce loss
Cons
- more applicable to HICs, as they have more money that they can spend on adapting and the quality of adaptation
- generic and unquantifiable ( cannot measure/ compare to quantifiable data to how good the management has been )
The park model
A model that shows the improvement or deterioration of quality of life pre, during and post a disaster
X axis = time
Y axis = QoL
Further explanation
The line of quality of life usually starts in the normality section and plateaus until a disaster strikes, this then will then drop showing the economic social and environmental damages the hazard has caused, however over time this line will then increase due to rebuilding and recovery of the hazard
This line depends on the severity of the hazard and the ability of the place to respond or their level of management
Ridge push
happens at constructive plate boundaries, it pushes a mid-oceanic ridge upwards. When the ridge is higher it is pulled down by gravity- pushing the ridge down.
slab pull
happens at destructive plate boundaries- the denser oceanic plate is subducted under the less dense continental plate, the slab of plate gets pulled away with it.
convection currents
heat from the core makes magma in mantle to rise towards the crust. When the hot current nears the crust, it begins to cool and sink towards the core. As this magma sinks, it drags plates across the surface of the earth by friction.
What was Wegners theory
-continental drift- continents have moved over time- tectonic movement
Evidence for Wegners theory
- The fit of the continents
-Similar geology of Brazil and west africa
-Fossils found in India are similar to those found in Australia - different volcanos form at different boundaries e.g shield and composite
-volcanos support tectonic theory as different lava types found- shield- basaltic. composite- rhyolitic
Evidence against wegners theory
Hotspots can develop below the surface and rise forming volcanos- which doesn’t support tectonic movement forming volcanos.
Hess’ seafloor spreading contradicted Wegener’s continental drift in that it involved the ocean sea floor moving as it expanded—instead of continents ploughing through the sea.
Conditions for tropical storms
60m deep water
at least 26 degrees oceans- hotter=more powerful
Winds are pulled towards the low pressure and as it rises it cools and vapour condenses into clouds
Coriolis effect spins the storm
Island arc- different to island chain
● Heavier plate subducts leaving an
ocean trench.
● Built up pressure causes underwater
volcanoes bursting through oceanic
plate.
● Lava cools and creates new land called
island arcs. e.g Mariana islands
Mudflows
- Mudflows (or lahars) are associated with the rapid melting of ice and
snow following a volcanic eruption (and associated geothermal activity)
(1). These only occur where there is a substantial amount of snow or
ice, typically at high altitude (1) (d). Lahars can also be triggered in
some locations by tropical storms following an eruption (1) (d). The
debris itself is comprised of water, volcanic ash, rocks. The lahar will typically flow down a valley side and occupy and river
channel valley (1).
nuées ardentes
Pyroclastic flow (also known as nuée ardente) - a super-heated mixture of gas and tephra that flows at speeds of up to 700 km per hour
This is one of the deadliest volcanic hazards as they can travel long distances and destroy everything in their path
Can destroy towns and buildings- Fuego volcano erupted in Guatemala in 2018
