Cause- This is another way of classifying hazards. Some hazards are natural, such as earthquakes or volcanoes caused by tectonic activity. However recently some hazards are not natural, they have been caused by man-made activities, such as increase inn greenhouse gases, causing increase in storms and cyclones, due to increase in global warming caused by human pollution. Also floods have been increased by human activities, due to high deforestation increasing the impacts of flooding. An example of this is the flash flood disaster which killed over 83 people on a campsite in Spain on 8 August 1996. This event was totally unpredictable and unexpected. This occurred in an MEDC country. This means that some classifications are not appropriate for LEDC and MEDC countries, however by knowing the cause it is likely to know the place where the hazard will occur. On the other hand increased human activity that is fuelling further hazards is making the places where the hazards are going to occur difficult to predict.
Hazards vary in distribution; this is why spatial occurrence is another type of classification. Some hazards occur in places related to their geographical areas, these are places they are most likely to occur. Tropical cyclones only occur in tropical parts of the world, and earthquakes and volcanoes occur in areas associated with plate boundaries. The scale of impact of these hazards varies from local to international, with some global impacts such as dust storms. The first hazard to affect the world globally was in Jakarta (Indonesia) on the 27th August 1883. Puzzled islanders were at the time unaware that the cause of their short day was one of the most violent volcanic explosions ever witnessed. The ancient volcanic island of lay 150 km to the west, in the strait between Java and Sumatra. On 27th August the volcano (long believed to be dormant) literally 'blew its top' in a violent explosion that was heard 2,000 km away in Australia. It threw an estimated 20 km3 of rocks and soil high into the atmosphere. Most fell as ash over an area of about 70,000 km2, but some was blown literally round the world. Exotic red sunsets throughout the world were being attributed to the volcanic dust in the atmosphere for many years after the event. The explosion also triggered off a giant sea wave () 40 m high, which drowned over 36,000 people in coastal towns on nearby Java and Sumatra, and could be detected on tide gauges as far away as the English Channel.
Krakatoa was the most powerful of the 5,567 recorded eruptions from 1.343 volcanoes active over the last 10,000 years. Between 1970 and 1986 50 to 70 a year occurred around the world.
The two main types of classification that will be assessed thoroughly are; Spatial occurrence and scale of impact. This is to asses their importance and which one is a better classification for hazards.
Spatial components of hazards are important, because it can affect the outcome of hazards. In 1994, an earthquake in Northridge, California occurred at 4:31 A.M, before roads were crowded with commuters; the death toll of 57 was probably much lower than it would have been hours later, this is an example of hazard occurring in an MEDC country, where spatial component affected the outcome of the hazard, although on this occasion the hazard didn’t affect many people, which is typical of an MEDC country when an hazard occurs, this is why the classification of scale of impact come in.
Spatial occurrence as a classification accepts that not all hazards occur in every part of the world. It is too cold for hurricanes in the artic regions, blizzards don not occur in tropical areas. These physical parameters are good classifications because it helps us to define the risks associated with the hazard occurring. The spatial occurrence in relation to geographical area helps to determine whether a particular event, fits the definition of a hazard. A 15cm snowstorm in Greenland would not be considered a problem, but if it was to occur in New York City, it could stop activities within the city, especially the service industry and fiancé in the city; it would disrupt trade and infrastructure and cause terrible loss to the city. Similarly freezing is not a problem in the tundra; however in sub-tropical climates it would be considered a hazardous event, especially to the primary industry.
Also the scale of impact of a hazard can affect a large number of people. For example; the tsunami of December 26 2004, which affected a large number of south Asia, South-East and South-West. This was the most deadly tsunami recorded in history and had the energy of 23,000 Hiroshima-type atomic bombs. This occurred in an LEDC and affected the majority of the world directly and indirectly. Directly affecting families, loss of livelihood, trade, health and indirectly affecting the MEDC concerning the loss of labour that went to the country to volunteer. Classifying hazards by spatial occurrence posses problems, since the level of hazard depend on land use and population density. An hazard occurring in a place such as Indonesia, or Bangladesh will be highly concentrated, while hazards in the Sahara will be diffuse. This raises the questions of how hazards are classified using spatial occurrence. Is a destruction of a small village by an avalanche in the Andes, the same as an earthquake in California or China? Does the use of spatial occurrence as a classification provide better insight into hazards?
Areas which have experienced hazards in the past should logically expect similar hazards to recur in the future - unless successful control measures (such as engineering schemes) have been adopted. Typical examples would include unstable hillslopes prone to , low-lying floodplains and coastal areas prone to , and regular storm tracks of . For example, the hurricane that occurred this year, September 21 2007. This hurricane was predicted and it’s path as not surprising. This means that spatial occurrence does work as an hazard classification, because it can be used to predict paths of volcanoes, which makes the impact of the hurricane less severe.
Similarly, areas which are known to be geologically active (like fault lines, earthquake belts or volcanic zones) Figure 1.3 pose greater threat than geologically unstable sites. The Kashmir earthquake (also known as the South Asia earthquake or the Great Pakistan earthquake) of 2005 was a major . The earthquake occurred at 03:50:38 on . The death toll was 73,276; most of the affected people lived in mountainous regions with access impeded by that blocked the roads, leaving an estimated 3.3 million homeless in Pakistan. 4 million people were directly affected, prior to the start of the winter snowfall in the region. It is estimated that damages incurred are over 5 billion.
The region where this earthquake occurred is not surprising since it is on four pate boundaries, figure 1.3. It is the scale of impact that caused the cost of the earthquake to be immense. This occurred in an LEDC country, where their perception of hazard is relatively low. Also the loss of lives and the primary industry affected it what questions if spatial occurrence is a better classification of hazards. As seen in previous case studies, the scale of impact in an MEDC country, regarding loss of lives is lower, than that of the LEDC. Spatial occurrence does not show the impacts of the hazards expect for where they occur, and it does not fit the definition of an hazard if man-made hazards are regarded. However, scale of impact relates more to the definition of hazards, and shows variations between the countries at different stages of development.