Global Hazards

Global Hazards

Natural Hazards AKA Physical Risks
1. Extreme hydrometerological and geohphysical events which impact adversely on people, the economy and society. They invariably result in death or injury, destruction of property and infrastructure and significant economic and social disruption
2. Hydro-meteorological hazards include Cyclones, Droughts and Floods
  1. Cyclones
    1. Any area of low atmospheric pressure that is created when air rises from the surface of the earth
    2. Causes - As the air rises into the atmosphere, it is cooled and condensation occurs. This may result in the formation of clouds and eventually precipitation, both of which re characteristics of low pressure systems. Cyclones can also bring about windy conditions and are associated with storms
    3. Effects - Destruction of Habitats Destruction of crops/property Death
  2. Drought
    1. An extended period of lower than average precipitation which causes water shortages.
    2. Droughts can be localised - occurring in relatively small regions or can be much larger - affecting entire continents
    3. Causes - When surface water shortages are not recharged or replenished for a number of consecutive seasons.
    4. Effects - Restriction of non-essential water Severe erosion results in desertification of an area, Dehydration, Disease, Death
  3. Floods
    1. An overflow of water that submerges on land which is very dry
    2. Floods occur when areas of land that are usually dry become inundated. In most cases, floods occur after a long period of prolonged rainfall. They can also occur in regions that have not experienced rainfall, they may flood because of rainfall running downstream or meltwater, e.g. Bangladesh
    3. Causes - Floods occur because the systems that are designed to cope with average levels of rainfall, such as stormwater drains and levee banks, simply fain to work properly because of a blockage or structural weakness.
    4. Effects - Loss of life, Damage to bridges, buildings, roads, homes Can also result in loss of power, contamination of water
  4. Hydro-meteorological hazards are natural hazards caused by water, the weather, or a combination of both
3. Geophyical hazards include Earthquakes, Volcanoes, Landslides and avalanches
  1. Earthquakes
    1. A series of vibrations on the surface of the Earth.
    2. Earthquakes occur at plate boundaries
    3. Causes - Earthquakes are caused by movements of rock within the Earth's lithosphere.
    4. Tectonic plates float on the layer of semi-molten rock (mantle) that lies underneath them. Heat generated by the Earth's core causes movements within the mantle, known as convection currents. These currents make the tectonic plates move, collide, drift apart or slide past each other which causes vibrations detected as earthquakes.
    5. Effects - Falling rppfs, people being trapped in collapsed buildings, loss of infrastructure and after shocks.
  2. Volcanoes
    1. An opening within the Earth's crust, from which material (magma, volcanic gases, ash and dust) from below the earth's surface is, of has been enjected
    2. Volcanoes occur at plate boundaries, around the pacific ocean (rim of fire)
    3. Causes - Heat from the earth's core heats up the surface of the volcano. The volcano forms by material being forced upwards by the movement of tectonic plates
    4. Effects - loss of crops, death, loss of houses, infertile land, volcanic ash and smoke
  3. Landslides and Avalanches
    1. The sliding of a large amount of rock or soil down a slope, under the force of gravity. An 'avalanche' usually refers to a sudden downward movement of snow or ice in a mountainous region
    2. Landslides can occur almost anywhere, they are also unpredictable
    3. Causes - possible triggers include heavy rainfall or earthquakes, Change to a slope that causes an increase in its steepness (such as road cutting) and clearing of vegetation could also trigger a landslide.
    4. Effects - loss of land structure, destruction of houses, death.
  4. Geophysical hazards are natural hazards caused by the physical processes that act upon, above or within the earth.

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