HAZARDS Flashcards
(29 cards)
PREDICTING earthquakes:
-there is currently no way to accurately predict earthquakes
-ways of monitoring or EWS (early warning systems) can monitor:
-land tilting
-altered levels of radioactive radon gas
-groundwater levels changing
-erratic animal behaviour
-remorse sensing or seismographs
HAZARD MANAGEMENT CYCLE
—>Prediction—preparation—HAZARD—response—-evaluation——risk assessment—>
PREPARATION for earthquakes:
-building design
-education (New Zealand’s “drop, cover, hold” posters)
-land-use planning
-earthquake drills
FORMATION of a COMPOSITE/STRATO-VOLCANO
1) when an oceanic plate and continental plate are travelling towards each other, due to the convection currents beneath the earth’s crust
2) .. the oceanic plate subducts under the continental plate when they meet, as the oceanic plate is denser and thinner
3)The subducted oceanic plate then melts to form new, less dense magma..
4) This then rises through the cracks and gaps of the continental plate, forming a magma chamber
5)the pressure in the magma chamber builds up due to the hot gases and rising magma
6) eventually, the great pressure in the magma chamber leads to an eruption, and the viscous magma erupts at the surface explosively
7) layers of ash and cooled lava as rock, form a stratovolcano
What is a HAZARD?
A hazard is an event that threatens or damages and causes destruction to people, their property and their settlements.
A NATURAL hazard is produced by environmental processes
Examples of biological natural hazards?
-pests
-diseases
Geological natural hazards?
-earthquakes
-tsunamis
-landslides
Climatic natural hazards
Storms
-floods
-droughts
Technological natural hazards?
-nuclear explosion
-cyber attacks
-transport accidents
VULNERABILITY?
A measure of how susceptible an area is to hazardous events due to locational features
RISK?
The likelihood of an event causing harm
Reasons why people continue to live in high-risk areas:
-a lack of education (uninformed on the real risks, particularly the case in poor, underdeveloped areas)
-unable to find jobs, or housing elsewhere
-unwilling to leave their community
-optimists that believe they will be unaffected, or people have resigned to their fate and the risks
-too much investment into an area to be abandoned
-the natural benefits outweigh the risk for some:
1) minerals from volcanoes such as gold, diamond, copper
2)fertile soil from volcanoes such ash acts as fertiliser
3) geothermal energy from plate margins
-the pull of tourism from the hazards can be attractive to businesses
Define: HOTSPOT
Hotspots are locations underneath the earth’s crust where strong and rising currents of magma (plumes) occur.
FORMATION of a SHIELD volcano:
1) at CONSTRUCTIVE/convergent plate boundaries, the plates move away from each other due to the convection currents beneath the earth’s crust..
2) the plates pull apart, exposing a gap where magma rises and erupts through to the surface as lava
3) the runny lava hardens and cools as rock on the surface,
4) this constantly continues, as more layers of lava erupt and harden, forming a gently sloping shield volcano
EARTHQUAKES at a TRANSFORM boundary
1) when two plates ar moving PARALLEL to one another, in opposite directions or with different forces…
2) The plates rub against each other and protrusions in the rock cause the plates to get STUCK, causing FRICTION which leads to a buildup of pressure
3) the pressure builds until eventually the plates are released and slip, also releasing the energy built up as SEISMIC WAVES
4) the place where the plates are released is called the FOCUS, and the place directly above the FOCUS at the surface is the EPICENTRE, where the effects of the earthquake is felt the heaviest
EARTHQUAKES at a DESTRUCTIVE/convergent boundary
1) When oceanic plates and oceanic plates move towards each other, due to the convection current’s beneath the earth’s surface…
2) the oceanic crust SUBDUCTS underneath the continental plate when they meet, as the oceanic plate is DENSER and THINNER
3) the subducting plate rubs against the continental plate, getting caught at PROTRUSIONS in the plates, which cause FRICTION and increases the pressure
4) the pressure builds and builds until finally, the plates BREAK. The place the plates break is called the FOCUS
5) The area directly above the FOCUS is called the EPICENTRE and this feels the effects of the earthquake the heaviest
6) When the plates are released, all the built up energy is also released as SEISMIC WAVES, which causes the earth to tremor
What happens at a COLLISION plate boundary?
1) when two plates of the same density are moving towards each other..
2) neither subduct when they meet, as neither is denser
3) instead the land is pushed upwards, and the land buckles up, causing FOLD MOUNTAINS
EXAMPLE: The Himalayas
How do TECTONIC PLATES move?
1) convection currents
2) slab pull
3) ridge push
EXPLAIN how convection currents cause tectonic plates to MOVE
1) hot magma in the mantle rises, exerting pressure onto the plates of the Earth’s crust
2) the magma diverts at the surface, pulling the plates with it to the left/right
3) the magma then cools, and sinks towards the core again, where it reheats and the process repeats
Explain how SLAB PULL causes tectonic plates to move
OCEANIC CRUST that is denser than CONTINENTAL CRUST, subducts under it at destructive plate boundaries
This creates a SUBDUCTION ZONE, that pulls the plates along with it,
Encouraging separation movement
Explain how RIDGE PUSH causes tectonic movement
When fold mountains/mid-atlantic ridges form, they exert weight onto the boundaries which encourages them to seperate
PRIMARY HAZARDS of a volcano
ASH:
-thrown explosively into air
-blankets everything + can kill crops
-causes respiratory problems (e, g can asphyxiate lives)
-can travel across regions and cause air traffic
LAVA FLOW:
-very slow
-molten
-magma that has reached the surface
-destructive to farmland, buildings, architecture
-few deaths due to slow speed
GASES:
-sulfur, CO, CO2
-gases can be toxic
-can cause respiratory diseases
-don’t travel too far
PYROCLASTIC FLOWS:
Pyroclastic flows are extremely dangerous, high-speed flows of hot gas, ash, and rock that erupt from volcanoes.
-move very fast + very high heat = very destructive
-causes death
SECONDARY HAZARDS of a volcano:
LAHARS:
-melted snow + ice mixed with volcanic ash to form fast moving mudflow
LANDSLIDES
-FIRES
-FLOODS
-INFRASTRUCTURE + TRANSPORT DAMAGE
-LOSS OF EDUCATION
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