In this essay I will look at the area of the volcano, the population of people around it, the viscosity and see how the human and physical can connect with each other. This is because the physical factors will decide the severity of the volcano and the human factors make the hazard worse. The first factor that I will look is the viscosity of the magma.
The viscosity will determine how violent the eruption is and what form the volcano becomes. The viscosity of the magma can be impacted by the temperature and the dissolved gases in the magma. The dissolved gases lower the viscosity of the magma. Another important part to consider is the silica content of the magma and lava. The flow of the lava will be impacted depending of the temperature.
If its high that means the magma is less dense allowing it to flow easily however if its low the magma will be more dense meaning that it won’t flow as well. Like the volcano in the DRC which is called Nyiragongo the magma in this volcano is of a very high silica connect this will make the magma more viscous. Magma of this high viscosity can cause eruptions that are very ferocious. The eruption in 2002 was like this and posed a great threat this is due to being very damaging.
This can plug the volcano causing the gases inside to be trapped which causes a lot of pressure to build up in the volcano and then it erupts brutally. The lava that does come out of the volcano can travel at 60km which means it can cause havoc to the local area. These eruptions are not that frequent and are not that easy to predict because of the rareness of them.
This means that when the 2002 DRC eruption did occur there was little to no warning of it happening. This means that the local people who do live close to the volcano will have no warning and be impacted the most. The volcano can also produce huge pyroclastic flows which is clouds of smoke and ash in the atmosphere, this is the reason for many deaths in the case for the DRC volcano 15% of the deaths were due to this.
On the opposite there is less viscous magma. The temperature is high being about 960C which is high compared with high viscosity. The magma due to the low viscosity make its move quickly. The eruptions are far less violent compared with the high viscosity magma be a lot more frequent.
It doesn’t pose as a high of a threat though as it cools a lot more quickly. Like Japan that rarely has lava based eruption but when they have occurred cause little damage to building because of the amount of lava that comes out of the volcano. The eruptions occur every day. The main danger is the tephra and pyroclastic flows that in one eruption killed 32 people and caused injuries to others.
The Japanese volcano Sakujumia is located on a convergent boundary with the Philippine plate converging under the Eurasian plate this is because the oceanic plate is more dense than the Philippine plate which is continental. This plays apart on why the eruptions can be violent not in the Lava sense but the pyroclastic flows. A volcano that is on a convergent plate boundary like another volcano in japan which is mount fuji this volcano contained andesitic lava which meant that the eruption that did occur at mount fuji was very destructive. This was because the lava has a viscosity. This shows that the viscosity is a major factor and does impact the hazard that a volcano can produce.
At a constructive margin the lava is not a viscous and therefore the hazard isn’t as severe. The location of the volcano is also a large variable in determining the hazard severity and the nature of its eruption. Location impacts what type of volcano is formed and so the viscosity of the magma. Therefore location is critical in determining the severity of the hazard posed by a volcano.
Volcanoes are generally found in these main areas. Convergent, divergent plate boundary and hotspots. The most explosive and most hazardous volcanoes are found on a convergent plate boundaries as shown before. One plate subducts beneath the other generating pressure and heat causing the rock to melt and the sediment to form an acidic magma chamber.
This magma is viscous is resistant to flow and results in violent dangerous eruptions. At the divergent plate boundary the lava is basic and therefore has not as high viscosity, allowing it to not cause as much damage and much less violent eruptions. 80% of the worlds volcanoes occur at destructive plate margins for example subduction of the Nazca plate beneath the south American plate to form the Andes. These are the most hazardous of all. To The main human factor that causes differences in the hazards posed by volcanoes is the people living near and around the volcano.
For example the DRC volcano many people make the decision to live near to the volcano because of the rich and fertile soil which is great for farming. Due to the DRC being a LIDC and does receive the most amount aid from the UN, many people rely on subsistence farming therefore are willing to risk the hazards that the volcano can produce.
Furthermore in the 2002 eruption 15% of the Goma was destroyed leaving 400,000 displaced. So they lost homes but also their livelihood. So showing that the hazards posed could have been reduced if the people chose to live elsewhere. However this is different around the world due to the differences in volcano types.
For contrast, the people of Italy live near mt etna yet due to the higher wealth of the country do not rely on subsistence farming. This is also because they are more educated and since Etna erupts quite often they have developed around the hazards of the volcano and have become used to the live near mt etna.
Etna is also less explosive than DRC volcano and therefore any hazard caused is greater in the DRC than in Italy. The human factors increased the severity of the hazard from each place. The perception of risk is a factor and can be the most important in measuring a volcanoes hazard. People do not just settle in close proximity to volcanoes because of the benefits that are volcano can produce but because their perception of the risk is low.
If people believe a volcano is being monitored satisfactorily or if think that the volcano will not erupt again for many years due to the inactivity of it. MT Etna is a very high monitored volcano in Italy, due to the high development of Italy and the tourism that is does bring. So this shows that the peoples perception of the risk of the volcano to be to low. This can impact the people as they can become complacent and might not realise a that the volcano could produce a violent eruption.
The main hazard to come from this is a false sense of safety around the volcano that has been inactive like the DRC volcano. The DRC volcano had been inactive for years and people didn’t perceive it to be a large risk. This is where people’s perception outweighed the risk the DRC volcano did pose. The ability to cope plays apart as well. Etna is in Italy which is much more developed and this shows that they have more economic power to deal with any damage caused by an eruption.
They experienced with dealing with an eruption in 1993 as they made people as safe as possible. With Etna not being too destructive there is less impact to Italy than the DRC with the main impact being the closing of major travel routes and grounding some planes. However in the DRC they could not cope as well due to the development of the country and relied on aid from other countries to be able to cope. The aid provided support and lowered the severity a little but could not stop the early impacts of the volcano. This can cause problems as well in the future for that country.
The volcano has a despairing impact on the economy with many local businesses and homes being destroyed meaning that the local economy of Goma has been hit hard by the volcano. So therefore because there perception of the risk was low meant that their ability to cope was reduced and that triggered the hazards of the volcano. This shows that the hazard was aggravated by the human impacts, the physical factors cannot be controlled so the human was the reason the hazard was so bad.
The physical and human factors are linked to the different impacts volcanoes do cause. Because of this that human factors are much more significant. The physical factors cannot be controlled or changed, we cant change the form of the volcano, the type or the lava it produces.
To conclude the human factors defiantly make the hazards worse. This is because of the perception people do have of the volcano. However the volcano itself is the reason why the hazard does occur. This could be that the lava is of high silica which would cause the threat level to be higher and the volcano to be more violent while volcanoes with low silica the volcano will pose less of a threat and be less violent. There are many physical factors that can contribute to the hazards a volcano produces. The changes in hazards caused by a volcano is by a combination of both human and physical factors.