Hazards Flashcards
(17 cards)
Constructive plate boundary
Plates move apart - causing earthquakes or magma to erupt from the gap. The lava escapes through the gap, cools and hardens to form a new crust.
Destructive/convergent plate boundary
Plates move towards each other. The denser, heavier oceanic plate subducts under the lighter, less dense continental plate.
Can cause volcanoes to form as the oceanic plate melts (friction causes it to heat when it subducts) - magma then rises to the surface through cracks.
Collision plate boundary
2 plates of similar density move towards each other. Neither is dense enough to subduct, so the land is pushed upwards. Causes fold mountains (like the Himalayas)
Earthquakes are main hazard.
Conservative plate boundary
Plates move past each other in opposite directions or in the same direction but at different speeds.
Earthquakes are only hazard here.
Causes of tropical cylcones
Sea surface temps over 27 degrees
Between 5 and 20 degrees N and S of the equator
Low wind shear
A deep layer of humid air
Stages of tropical cyclone formation
- Warm, moist air rapidly rises forming an area of low pressure.
- Air from high pressure areas rushes in to take the place of the rising air.
- This air then warms and rises forming a continuous flow of rising air.
- As the air rises it cools and condenses
- The Coriolis force causes the rising air to spiral around the centre
- Tropical cyclone moves westwards from its source.
Features of tropical cyclone
Heavy rainfall
High wind speed
Storm surges
Calm eye
Highest winds and heaviest rain in the wall of the eye
Diameter up to 1000 km.
Shield volcano
Formed at constructive plate boundaries, where the lava is runny - low viscosity. Form shield volcanoes with gently sloping sides
Strato volcanoes
Formed at destructive plate boundaries - high viscosity lava that runs slowly. Forming a steep slope.
Volcano primary hazards
Ash
Pyroclastic flows
Lava flow
Gas emissions
Volcanic bombs
Volcano secondary hazards
Lahars - water mixes with volcanic ash to create a fast moving mudflow
Acidification - sulphur emissions from volcanic eruptions increase the acidity of water
Landslides
Fires
Earthquake primary and secondary hazards
Primary hazards:
Ground shaking
Secondary hazards:
Collapse of buildings
Landslides
Gas leaks
Fires
Liquefaction
Subsidence - sinking of the Earth’s surface
Mudflows
Tsunami
Epicentre?
Point directly above the focus on the earths surface.
Reasons for living in hazardous regions
Fertile soil in volcanic areas
Geothermal energy
Trade
Jobs
Tourism
Lack of money
Vulnerability of countries
-exposure to natural hazards
-susceptibility
-capacity to cope
- capacity to adapt
ECONOMIC FACTORS
- wealth and level of development
- insurance
- buildings/quality of buildings
- technology - for warning and monitoring
SOCIAL FACTORS
- population density
- education
PHYSICAL FACTORS
- global location e.g. near plate boundaries
- physical environment (coastal environment susceptible to tsunamis)
Earthquake preparation?
Building design - cross bracing of steel frames,
strong foundations, reinforced walls and rubber shock absorbers to reduce tremors.
Earthquake preparation drills (drop cover and hold) and emergency planning - mapping areas most at risk.
Remote sensing and GIS
- Geographical Information System gives data on vulnerable areas, land use and infrastructure such as roads. GIS can also be used to asses risks to population, recommending mitigation and sear cand rescue prioritisation.
What are hotspots?
Locations beneath the Earth’s crust where strong and rising plumes of magma occurs. Where the crust above a plume is weak, volcanic activity occurs.
