Characteristics

Natural Process or Event: A physical process that takes place, but poses no threats to humans or their property e.g. a volcano on an uninhabited island.

Natural Hazard: A natural process or event that has the potential to cause loss of life or injury or damage to property.You can also get manmade hazards like nuclear accidents or chemical spills.

Natural Disaster: The realisation of a major hazard that has caused significant loss of life/injury and/or damage to property.

The IB also talks about a hazard event which they also say is the realisation of a hazard.

Hazard Classification

Hazards can be simply classified as human and physical, or they can be classified in a number of different ways. Here is one possible way:

Physical	Human	Combination or Either	Biological
Earthquakes Volcanoes Tsunami Tornadoes Hurricanes Meteor strike	Nuclear accident Gas explosion Car accident Chemical leak	Acid rain Forest fires Landslides Avalanches Drought Global warming	HIV/AIDS Malaria Animal attacks

Another classification developed by Keates and Burton is below. They only look at natural hazards

Geophysical	Geophysical	Biological	Biological
Climate and Meteorological	Geological and Geomorphological	Floral	Faunal
Droughts Floods Heatwaves Tornadoes Hurricanes	Earthquakes Volcanoes Mass movements Tsunami	Hayfever Plant infestations Poisonous plants Fungal diseases	Animal attacks Bacterial and viral diseases Animal infestations

Another Classification of Hazards

Hazards can also be classified by some of their major characteristics. These characteristics can determine how severe the hazards are.

Duration: The length of time that a hazard lasts for. As a general rule the longer the hazard the more severe it is likely to be. For example and earthquake that lasts 1 minute is likely to be more severe than one that last two seconds and a drought that lasts ten years is likely to be more severe than one that last three months.

Magnitude: This is the strength of a hazard. Most hazards are measured on a scale e.g. the Richter scale or the volcanic explosivity index (VEI). Generally speaking, the stronger the hazard the more severe the hazard is.

Predictability: Some hazards are easier to predict than others. For example, volcanoes normally give warning signs before they erupt and tropical storms can be tracked from development to landfall. However, others like earthquakes are much harder to predict. Generally speaking hazards that hit with no warning are going to be more serious.

Regularity: If hazards happen often and in quick succession e.g. a earthquake followed by multiple aftershocks then then the severity is likely to be greater. During hurricane seasons, countries can be hit by repeated storms each causing greater damage because it has not been possible to recover from previous damage.

Frequency: The return interval of hazards of certain sizes. For example earthquakes with a magnitude of over 8.0 happen on average once a year, but earthquakes of only 3 or 4 happen many times a day. If the hazard is a less frequent strong event, then it is going to have a bigger impact.

Speed of onset: If the peak of the hazard arrives first or arrives quickly e.g. an earthquake, then the affects are likely to be worse than one that arrives slowly e.g. a drought.

Spatial concentration: Where hazards are located or centred. For example earthquakes tended to be focused along plate boundaries, whereas tropical storms tend to be located in coastal areas in the tropics. Hazards that are located in known areas can be better prepared for and managed better.

Areal extent: If a hazard covers a large area e.g. a drought covering the whole of East Africa, then the severity of the hazard is likely to be more severe, than a flood hitting just one village.

Number of hazards: If a location is hit by multiple hazards that the affects can be more severe. For example hazard hotspots like Indonesia can be hit by earthquakes, volcanoes, landslides and flooding all simultaneously.

As a general rule as the magnitude of a hazard increases, the frequency of the hazard happening actually decreases. This can be seen in diagram A where there is a negative correlation between frequency and magnitude. Diagram C shows that some hazards tend to be low frequency/high magnitude events e.g. tsunamis, whereas other hazards tend to be high frequency/low magnitude e.g. floods. However, it is important to remember that these graphs are generalisations and that some floods like the 2010 Pakistan floods can kill and injure hundreds while some tsunamis may have no impact on humans.

Natural Hazards and Hazard Hotspots Although natural disasters like earthquakes, volcanoes and tsunamis normally grab the news headlines, they are often not the hazards that cause the most damage and loss of life. Although it is very hard to accurately collect global data on deaths caused by natural disasters, the figures below show that floods, storms and droughts were far bigger killers than earthquakes or volcanoes between 1980 and 2000. The map to the right shows some of the major disasters that hit the world in 2010. By looking at the map its is obvious that some countries and regions suffer from more hazards than others. A country that suffers from multiple hazards is known as a hazard hotspot. El Salvador, Indonesia and the Philippines are all considered to be hazard hotspots because they can suffer from: Earthquakes Volcanoes Landslides Tropical storms Floods Tsunamis