PLAN:
1. What is a hazard- volcanic hazards include tephra, lava, pyroclastic flows, volcanic bombs and seismic hazards include earthquake, tsunami, liquefaction, landslides
2. Human issues- proximity to lowland coast, ability to adapt to change, socioeconomic effects, impacts within a community, difference in rich and poor, urban and rural, ability to cope with a disaster, willingness of people to aid
3. Physical issues- type of plate boundary, frequency of events
4. Case studies: Volcanos: Nyiragongo, Mount Etna; Seismicity: Japan, Haiti
A hazard is a physical or man-made event which adversely affects human life, business, and events. Volcanic hazards may include lava, pyroclastic flows and volcanic bombs whereas seismic hazards may include earthquakes, tsunamis and liquefaction. Humans attempt to mitigate the effects of volcanic and seismic events via predictive methods but the extent to this may be reliant on the country’s financial status.
A volcanic or seismic hazard can have an effect on all people from differing economic backgrounds and the extent of the disaster if often directly linked to the magnitude of the earthquake or the areal extent of the volcanic eruption. This is therefore a result of the occurrence of type of plate boundary. A volcanic eruption produced at a destructive plate boundaries is likely to be much more devastating than at a constructive. This occurs because the volcano is usually composite and therefore expresses rhyolitic lava with low silica content and therefore erupts unpredictably and with great force. At this plate boundary, a denser plate (e.g. oceanic or and older plate) subducts a less dense plate (continental or newer) and this plate descends into the asthenosphere. The plate melts at the Benioff zone due to increased temperatures and pressures and stress is released as an earthquake. Indeed it is also true that earthquakes are the most severe at destructive plate boundaries. Furthermore, the magma from the melted plate rises and erupts on the surface as a volcano e.g. Montserrat caused by the subduction of the Atlantic plate beneath the Caribbean and erupted with a Volcanic Explosivity Index (VEI) of 3.
Volcanoes are also evident at constructive plate boundaries, e.g. mid-Atlantic Ridge, where two plates diverge allowing magma to rise at the surface forming shallow sided sloped volcanoes. The Island of Surtsey in Iceland was produced after an eruption in 1962. While these type of volcanoes aren’t as explosive, they couldn’t affect a larger area because the lava is runnier due to a lower silica content and therefore can spread large distances. Furthermore, earthquakes may also be produced at constructive plate boundaries, where two plate move past each other and different rates and get stuck. When one plate jerks forward, the friction is released as an earthquake and this plate boundary is shown at the San Andreas Fault which experienced an eruption in 1998 which showed as 6.3 on the Richter Scale. Los Angeles, a developed country, lies on this plate boundary and affects like death toll (57 people died) and loss of electricity and gas where common factors during this event and are also common place in any seismic hazard across the world.
A hazard, as the definition suggests, must affect people and therefore we can assume that if there are no people, the hazard is not present. If this is correct, then moreover, a region with a high population density is likely to experience greatest impacts as there are more people to experience the hazard. For example, a region like Haiti which has a population density of around 370 per people km2 is likely to experience worse impacts e.g. higher death toll, than a region like Japan with a population density of around 300 people per km2. Indeed, the death toll in Haiti was near 200,000 more than in Japan.
However, Japan and Haiti are at two different ends of the economic spectrum and therefore it is wrong to assume that just population density influences the impact and therefore development must also be crucial. Japan has the 3rd largest economy in the world at $38,000 opposed to around $1500 in Haiti. A region that is more developed with a higher gross domestic product (GDP) has more available funds to invest in predictive methods like radon gas emission testing or seismometers. Indeed, 60% of the monitoring stations in Sicily are located on Mount Etna’s slopes which provides the residents with up to 12 hours warning prior to an eruption in order to evacuate and gather supplies like food or water. This is extremely beneficial in reducing the death toll as it minimises the number of people in high risk zones and reduces injuries or deaths. Furthermore, more protection is available in developed countries such as the construction of aseismic buildings (as was present during the 2011 Japan Earthquake) - figure 2, or land use planning which allows construction of buildings away from hazardous zones, again preventing large populations in high risk areas. The 15,000 deaths during the 2011 Honshu earthquake in Japan was largely the result of the subsequent tsunami and not due to the collapse of buildings during the earthquake. Furthermore, economic development also allows communication networks and therefore much quicker evacuation if messages are broadcasted across the country. In Japan, a tsunami warning was sent out to over 50 states which allowed many residents to move to higher ground.
On the other hand, physical factors may also play a role such as the coastal geography. If there is low lying coastal areas, these are vulnerable to tsunamis as they offer little protection. The severity of the tsunami hazard is again also worsened by the population density near to these low-lying coastal regions. Furthermore, the frequency of the events also may affect the extent of the impact. An area which experiences constant earthquakes or eruptions is unlikely to be able to adapt to the change quickly enough to alleviate the issues such as spread of cholera and rebuilding businesses and homes. This was apparent in the Nepal earthquake in April where a second earthquake of magnitude 7.0 was experienced 2 weeks after the first eruption and many streets remained in rubble or the problem worsened. However, a region that does experience frequent eruptions, such as Mount Etna which erupts approximately once a year, may invest more of the GDP into mitigating seismic or volcanic hazards, than a region that rarely receives them e.g. the UK. However, it is extremely evident that regions that already suffer from other issues like poor healthcare or infrastructure due to low GDP are much more likely to invest finances into these sectors.
There are also variations of impact within a community. For example, a region that is dominated by informal settlements will experience more collapse of buildings and loss of homes or business. This may have a negative spiral effect and lead to increased poverty as the residents will have no income. Furthermore, pollution of the water supplies may also cause spread of disease e.g. cholera which caused 6000 deaths in Haiti 2010 but also pollution may affect the crops in the local area resulting in lack of food which is critical considering the basis of the industries in these areas are agricultural and also the residents rely on the food for themselves. Moreover, a region that is much more urbanised within a community may be able crucial to resist earthquakes to a greater extent and will experience less secondary effects like liquefaction due to improved surfaces and building structures.
It is clear that the above impacts have had worse effects on developing regions and this can also be further worsened by the willingness of foreign regions to provide aid. Indeed, during the 2002 eruption in Nyiragongo, around 200 people were killed due to toxic gas emissions, and the lava itself. UNICEF warehouses were lost during the eruption and therefore issues arose with lack of medicines to treat disease, and homelessness. Even though the issues could be seen, foreign countries were unwilling to provide aid because they were concerned about corruption of governance which is a key theme in many developing regions. Meanwhile, the 2011 Japan eruption, which was very successfully adhered to by the Japanese Government who immediately send out fighter jets to assess damage and also prevent the collapse of the Japanese Yen, was met with inundations of aid from 91 nations and also charity organisations such as Save the Children.
In conclusion, volcanic and seismic events do have the greatest impacts on the world’s poorest people due to lack of resilience to the event, and lack of aid. The informal structures place a huge threat on development and with the reoccurrence of hazardous events, they are unlikely to develop without serious consideration on improving infrastructure and of course this is extremely difficult without improving the economy.
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