Hazards
- Created by: Pepe565
- Created on: 02-04-18 11:17
Types of Hazards
Types of Natural Hazard -
GEOPHYSICAL (earthquakes, landslides, volcanoes, tsunamis)
ATMOSPHERIC (cyclones, drought, storms)
HYDROLOGICAL (floods, avalanches)
Perception of Hazards
Factors in the Perception of Hazards...
- WEALTH - richer people can better avoid hazardous environments
- RELIGION - some think it is an act of God
- EDUCATION - more understanding of hazards, maybe believe they can mitigate
- PAST EXPERIENCE -affects perceived risk of hazards
- PERSONALITY - some fear hazards, some see them as exciting
Characteristic Human Responses
Responses to Hazards
FATALISM - "hazards cannot be avoided, they must be accepted"
PREDICTION - working out where/when the hazard will occur
ADAPTATION - adjusting to living with the hazards
PREVENTION - stopping hazard occurring/reducing its magnitude. Not always possible eg/ volcanoes
RISK SHARING - sharing costs of reducing hazard eg/ insurance against hazards - not everyone will claim, cost = shared
MITIGATION - reducing impacts of hazard. May involve prediction to aid evacuation. May be adaptation - adapting buildings to withstand hazards
Park Model
PARK model - responses to hazards
1.) Pre-disaster - the norm
2.) Disruption - during/ directly after an event - destruction of property, loss of life, no response yet
3.) Relief - immediate response, rescue efforts focus on saving people + preventing more damage
4.) Rehabilitation - resolving long-term problems
5,) Reconstruction - rebuilding permanent houses, infrastructure
Buildings either be built to same standard (return to normal). Built to higher standard, area improves
Hazard Management Cycle
4 stages:
- Mitigation - minimise impact of future hazards (flood defences, fire resistant roofs)
- Preparedness - planning how to respond to hazard (warning systems/education)
- Response - reaction after hazard. (emergency services rescuing, evacuation)
- Recovery - getting back to normal (repairing/rebuilding homes, restoring services
Earth's Structure
INNER CORE, OUTER CORE, MANTLE, ASTHENOSPHERE, CRUST
Inner core = solid ball (iron + nickel)
Outer core = semi-molten (iron + nickel)
Mantle = silicate rocks. Mantle near core is rigid, asthenosphere crust is semi-molten (can flow)
Crust = outer layer of Earth. 2 types: Continental (thicker, less dense) + Oceanic (thinner. denser)
Earth's surface separated by tectonic plates, where they meet = plate boundary
Main plates; North American, Pacific, Eurasian, African, Philippine, South American, Nazca. Antarctic, Indo-Australian
Plate Movement Theories: Convection Currents
Mantle next to core is hottest, so lower parts of asthenosphere heat up and rise.
Once they get to the top they cool.
Creates circular movements aka convection currents, moving the plates above.
Plate Movement Theories: Slab Pull
Denser oceanic crust subducted at destructive margin.
The sinking of the plate edge pulls the rest of the plate.
Plate Movement Theories: Ridge Push
At constructive margin, magma rises, forms new crust on a slope.
New crust cools and gravity moves rock downslope away from margin.
Pressure put on plates causing them to move apart
AKA gravitational sliding.
Plate Movement Theories: Sea-floor Spreading
Plates move apart, magma rises to fill gap, forms new crust.
Over time, that new crust is dragged apart, even more magma comes.
When this happens undersea = sea-floor spreading, creates mid-ocean ridges
What happens at each plate margin? CONSTRUCTIVE
CONSTRUCTIVE = plates moving apart
Magma less dense than plate above it - rises to form a VOLCANO
Plates move apart at different rates, building pressure. Causes fault line and EARTHQUAKES
Diverging plates underwater = Ocean Ridge (eg Mid-Atlantic), underwater volcanoes
Plates diverge beneath land, rising magma causes fault lines. As plates move apart faults drop to form Rift Valley.
Volcanoes form at rift valleys (Eg Mt Kilimanjaro)
What happens at each plate margin? DESTRUCTIVE
DESTRUCTIVE: plates moving towards each other (converging)
Oceanic vs Continental - denser oceanic is subducted, forms deep-sea trench. The part of the oceanic crust melts into magma, rises = VOLCANO. As plates move past each other they can get stuck, pressure builds, released as an EARTHQUAKE.
Oceanic vs Oceanic - Denser of the 2 oceanic crusts gets subducted. Again makes deep-sea trenches, earthquakes, volcanoes.
Continental vs Continental - neither subducted. Pressure builds can cause earthquakes or fold mountains as they are forced up.
What happens at each plate margin? CONSERVATIVE
2 plates lock together, pressure builds, released as an earthquake.
Eg/ San Andreas Fault
Volcanic Hazards
Constructive
Basaltic. Frequent, not violent. V hot and runny
Destructive
Andesitic/ rhyolitic. Not frequent, but violent.
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