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The number of fatalities that result from volcanic and seismic natural hazards is related to the level of development in the country in which they occur. Discuss. A natural hazard is an event, linked to the physical environment, which is considered to have a negative effect on humans. The event is also seen to be unpreventable by humans. However, an event such as a volcanic eruption that has no effect on human beings is considered a natural phenomenon rather than a natural hazard. It is the presence of humans, in an area that such an event occurs, that allows it to be termed a hazard.
Although humans cannot prevent these occurrences, they have a role to play in the event’s extremity as a natural hazard. For example, volcanic eruptions have been present throughout history, but it is not until settlements are built on the rich soils they form that they become a hazard. This essay I will evaluate the extent to which the level of development in a country affects the number of fatalities caused by volcanic and seismic natural hazards. A volcanic natural hazard is a volcanic eruption.
Volcanoes are formed at convergent and divergent plate boundaries and also at hot spots. At convergent plate boundaries eruptions tend to be from a vent, as oceanic crust is forced beneath another plate, the extremities of heat and pressure leads to the partial melting of the crust which is being submerged. The magma formed from oceanic crust is less dense than (due to its high water content) the mantel and rises up through the vent (this can be seen in figure 1). The lava is generally acidic and is also viscous. This means that eruptions are usually, violent and unpredictable.
At divergent plate boundaries the eruptions are from a crack. The eruptions are intermittent and not very violent as the lava has a low viscosity and acidity. Hot spots are volcanic regions where the underlying mantle is thought to have a higher temperature than the surrounding magma allowing it to rise up, hot spots may form island chains are arcs. (illustrated in figure 3) A seismic natural hazard, is most commonly thought to be an earthquake, however an earthquake can be the cause of many other natural hazards, such as tsunamis.
An earthquake is a sudden release of energy in the earth’s crust creating seismic waves. Irregularities on faults that are moving past cause frictional build up, when their force against one another build to a high enough degree they lurch past one another and the pressure is released as seismic waves causing an earthquake. A similar process occurs at submergent plate margins. Volcanic eruptions, though unpreventable, can be predicted. Prediction allows a plan of action to be formulated to protect the population of a country.
To predict an eruption many factors must be take into account, seismic shockwave patterns, hazard mapping, sampling of lava and gas emissions and remote sensing of changes to the geography of the land and heat and gas emissions (these methods are illustrated in figure 4). To protect the population, actions to reduce possible damage and instruct people on what precautions are thought to be necessary must be taken. Longer term protection might involve land-use planning to minimise the impact of future hazards. Chile is located in South America and has a population of approximately 16,888,760.
It is classed as a relatively less developed country. In 2008 on the 2nd of May a volcano in south eastern Chile erupted, called Chaiten (it’s location in relation to plat boundaries can be seen in figure 5), a caldera, one of the most explosive forms of volcano. Chaiten has formed due to the presence of the subduction zone where the Pacific plate is being forced beneath the South American continental crust (this process can be seen in the simplified diagram in figure 6). The volcano, which had a lava dome 2. 5km wide and 4km long, is formed from viscous rhyolitic lava.
A 17km high column of volcanic ash and steam was produced by the preliminary eruption; the column was carried into Argentina and over the Atlantic. The town of Chaiten is located 10 km south-west of the volcano and was covered with ash. Approximately 4000 people who lived there were evacuated, with an additional 1000 people from a nearby town, by boat. Before this eruption Chaiten was classed as low risk as the only eruption prior to this was 9400 years ago. Although it had a history of explosive eruptions, this extended period of dormancy, the remote location of Chaiten and its low population density, meant that it was of low priority.
Chile has only one volcano observatory to its 20 volcanoes and there was no time monitoring of the reaction until the USGS arrived on 16th may 2008. Necessary evacuations, some forcible took place by sea. Emergency measures were as follows; residents in the area were warned not to drink the water as it had been polluted by ash; officials allocated clean water and protective masks; a 50km exclusion zone around the town was ordered; families were issued a monthly disaster stipend between $1,200 and $2,200 by the government and financial aid was granted to small businesses.
The event had a range of impacts. When the ash plume collapsed, it brought a large amount of ash to the ground. This ash coated and asphyxiated a number of animals, leading to their deaths, and blocked roads. The eruption triggered a thunder storm and the heavy rainfall combined with the ash to cause flooding, by may 14th it was reported that 90% of the town of Chaiten was flooded. 80 to 90% of the town was damaged and 20% was completely destroyed. The mixing of ash and heavy rainfall also created lahars, which effected communications and made access difficult.
There was damage to airports and flights were grounded. Despite this, there were few casualties (hospitals treated some for breathing difficulties) and only one fatality, which was accredited to stress. Mount Etna is Europe’s highest (3310m) and most active volcano. It is situated on Sicily, Italy (a well developed country) (It’s location in relation to plate boundaries can be seen in figure 7). Mount Etna is associated with the subduction of the African plate under the Eurasian plate, which also produced Vesuvius and Campi Flegrei, but is part of a different volcanic arc.
It is a composite stratovolcano, which erupts basalt lava of low viscosity. Sicily has a population of 5,050,486, 25% of this population lives on Etna’s slopes. In 2002-3 major eruptions created a huge ash plume which deposited material 600km away in Libya. The eastern flanks of the volcano shifted 2m damaging housing. In 2006-7 major lava fountaining occurred, with ash emissions. In May 2008 earthquakes accompanied the opening of a fissure and the eruption of lava flows that travelled 6km.
Due to Etna’s regular eruptions throughout history the people who inhabit its slopes are experienced in managing the eruptions, there if often little government intervention unless a densely populated area is threatened for example Zafferana by the lava flow in 1992. In 2002 dams of soil and rock were installed to protect the tourist centre. The Italian Army’s earthmoving equipment was used to block and divert lava flows. The government immediately made allowances for $8m in financial assistance and tax breaks for villagers.
Due to it’s frequent eruptions, Etna has been monitored more closely than Chaiten. It has been monitored by the INGV for 20 years by remote sensors. Data is continuously recorded and observations made to evaluate volcanic activity levels and issue warnings. Many other measurements are also taken so that warning may be given as early as possible. In 2002 the eruption destroyed the tourist station at Piano Provenzana and part of another. On 4th September 2007 the airport of Catania was forced to close due to runways being covered in ash.
Winter tourism was affected, as visitors stayed away due to concerns for their safety. When the volcano flanks slipped, there was structural damage to many houses. There were also losses to agriculture as the fertile volcanic soils support a large amount. It has been estimated that only 77 deaths can be attributed to Mount Etna’s past 190 eruptions and in the most recent eruptions there have been no fatalities. It is not yet possible to predict earthquakes accurately, there are however methods that are used to predict when an earthquake is impending.
Seismic records are used to find patterns of earthquakes to predict when the next one is likely, however this suggests that irregularities at plate margins will always be constant. Radon gas is measured as it will be released more quickly from granite and similar rocks when they are deformed by shifting. Ground water may rise independently of atmospheric conditions. Protection methods include; making buildings earthquake resistant; educating the public about disaster prevention; improving earthquake predication; implementing better evacuation plans and reducing the risk of fire.
Bam a city in south-eastern Iran (an LEDC) and the surrounding Kerman province, was hit by an earthquake measuring 6. 6 on the Richter scale (plate boundaries related to Iran are shown in figure 8) on December 26th, 2003 resulting in the deaths of over 43,000 people and leaving over 60,000 people homeless. Bam has a population density of 78/km2, Bam has a population of 73,823. Many of the mud-brick buildings in Bam collapsed resulting in the high loss of life. The mud-brick crumbles easily into rubble, making rescue difficult.
Many survivors were left destitute on the streets, some forced to spend the cold nights wrapped in blankets; some were given tents, others made use of any shelter they could find. 90% of the buildings in the city were completed destroyed. After the quake there was criticism of the coordination of relief efforts by the government and of the lack of preventative measures. The Iranian press spoke out about the controversy surrounding this and the lack of a national plan to make buildings quake proof. Following the earthquake, ‘tented cities’ were constructed on the outskirts of the city by relief workers to try and house the many homeless.
As well as struggling to survive in the below freezing temperatures of the Iranian winter, there were concerns relating to the poor access to good quality sanitation, with many sharing outside toilets and a lack of clean water. However, it is believed that the freezing temperatures may have helped to reduce the incidence of water borne disease. With large numbers of volunteers coming in from all over Iran, the main plea for help after the earthquake was for medicine and equipment to help the tens of thousands injured in the quake.
There were a number of reasons for the high death toll; poor construction of buildings; lack of earthquake proof buildings; buildings made of mud-brick (collapse easily into rubble); lack of enforcement of building codes / regulations; lack of research into techniques to protect the buildings from earthquakes; population boom and competition for houses (resulted in rapid building of sub-standard housing); lack of national plan for the event of a disaster and extreme cold temperatures made conditions for survivors difficult.
On 12th of May 2008 an earthquake of a magnitude 7. 9 on the Richter scale hit 90km west/north-west of Chengdu, Sichuan, in south-eastern China (an NIC that is recently being considered an MEDC). Sichuan has a population of 80,418,200 and a population density of 180 /km2. Sichuan is a largely rural area, but has 5 main cities. This earthquake resulted in a death toll of 70000 by June 2008.
The shaking of the ground in the area around the epicentre was intense and resulted in 1. 5km of surface faulting near Quingchuan. An after shock with a magnitude of 5. 4 was measured that resulted in another 8 deaths, 927 injuries and destroyed 400000 homes. Though the area is prone to earthquakes, they do not appear to have been prepared for a strike of this magnitude.
Over 45 million people in 10 provinces were affected and 15 million people were evacuated from their homes; over 5 million buildings were destroyed and 21 million damaged in Sichuan which left at least 5 million people homeless; some towns were completely destroyed; the total economic loss was estimated at $86 billion; transport links were destroyed making it hard for rescue workers to access the area; rivers were blocked by landslides, which when paired with heavy rainfall resulted in serious flooding and 8 schools were toppled, trapping school children.
The extremely high death toll can be partly attributed to the fact that the earthquake was not predicted. China’s economic rise has had little effect on this area, and many of the buildings were not built to withstand earthquakes. Despite these set backs the government responded immediately and sent 80000 troops to organise the rescue efforts. The mountains meant that some troops had to be parachuted into the remotest areas. Secondary threats emerged from the barrier dams, the soldiers solved this by using explosives to divert the water into earthquake damaged towns.
The disaster was too larger for the Chinese government to deal with alone, The Chinese government allocated 95 billion yuan in aid relief and foreign and domestic donations yielded 55 billion yuan. Volcanic natural hazards have in the past caused a high fatality rate, but in recent times in both MEDCs and LEDCs it has generally been low, due to advancement in prediction techniques and equipment and improved evacuation plans being made available to both.
In relation to seismic natural hazards Iran and China both had a high death toll though the MEDC (China) had a higher death toll, the earthquake had a greater magnitude and the area in which it occurred was more densely populated. That the buildings in China had not been made earthquake resistant shows that a country being an MEDC does not mean that all areas will benefit. That the earthquake was not predicted can be attributed to the low reliability of prediction methods, there is a chance that if it had been predicted appropriate areas would have been evacuated and the number of fatalities would have significantly decreased.
To conclude, these case studies show little relationship between the number of fatalities caused by seismic and volcanic natural hazards and the level of development in a country.
Sources of information: http://environment. nationalgeographic. com/environment/natural-disasters/volcano-profile/ http://en. wikipedia. org/wiki/Hotspot_(geology) http://en. wikipedia. org/wiki/Earthquake#Naturally_occurring_earthquakes http://www. extremescience. com/calderas. htm http://geology. com/volcanoes/etna/ http://www. bbc. co.uk/scotland/education/int/geog/envhaz/volcanoes/prediction/index. shtml http://en. wikipedia. org/wiki/Mount_Etna#Recent_Eruptions http://geology. com/volcanoes/chaiten/
Text book Google images http://www. nextearthquake. com/ http://geobytesgcse. blogspot. com/2007/01/case-study-of-earthquake-in-ledc-bam. html http://en. wikipedia. org/wiki/2003_Bam_earthquake http://www. guardian. co. uk/environment/2003/dec/27/iran. naturaldisasters4 http://www. edu4hazards. org/earthquake/earthquake. html http://news. bbc. co. uk/1/hi/in_depth/asia_pacific/2008/china_quake/default. stm.