Volcanoes

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Introduction

            A volcano refers to a geological feature caused by the formation of a vent on the earth's crust, thereby permitting the escape of volcanic ash, hot lava, and gases from the magma chamber located beneath the earth’s surface. Volcanic activities typically happen at the point of intersection of the Earth's tectonic plates. The type and shape of the volcano formed are thus dependent on how these tectonic plates move (Geoscience Australia 2017).

Causes

            Various factors are responsible for triggering volcanic eruptions but the three predominant ones are magma buoyancy; magma pressure due to exsolved gases; and the addition of new magma to the already full magma chamber (Gonnermann & Manga 2014). Magma buoyancy

Melting of the rock inside the earth causes an increase in volume even as its mass remains constant. Consequently, this yields a melt of a lesser density relative to the surrounding rock. On account of the difference in density, the lighter magma moves towards the earth’s surface due to the effect of buoyancy. In case the rising magma has a lesser density than that of the earth's surface, it erupts upon reaching the surface (Gonnermann & Manga 2014).

Magma pressure due to exsolved gases

Certain magmas such as those of rhyolitic and andesitic compositions also contain such dissolved volatile compounds as sulphur dioxide, water, and carbon dioxide. Experimental studies reveal that at atmospheric pressure such magma has zero solubility (Dobran 2012). However, this solubility increases as the pressure rise. As the magma rises towards the earth’s surface, there is a resultant reduction in its solubility, leading to the separation of water from magma. As this magma approaches the earth’s surface, more water leaves the magma, leading to its disintegration into solid and molten fragments, thus forming explosive eruptions.

Addition of new magma

The addition of new magma into an already full magma chamber could also trigger the movement of magma towards the earth’s crust, and hence an eruption at the earth’s surface (Scientific Americans 2017).

Impacts

Social

            Some of the social impacts of volcanoes include loss of lives and property and destroyed human settlements resulting in displacement. For example, the December 29, 2013, volcanic eruption in Chaparrastique, El Salvador, resulted in the evacuation of all individuals situated within 2 miles of the eruption. 

Economic

            Various volcanic eruptions provide beautiful and extraordinary natural sceneries that can be of economic value to the community if they are converted into tourist attraction sites. In addition, locations, where volcanic activities happen, are characterised by a high potential for geothermal energy, and this could not only act as a source of revenue to the locality but could also lead to economic growth in trying to tap this natural resource (BBC 2014). When the lava and ash break down, it adds nutrients to the soil and hence acts as an ideal site for agricultural activities.

Pyroclastic flows and lava flows also lead to the destruction of buildings, not to mention the destruction of water supplies and crops. Consequently, both the public and private sectors incur the costs of evacuating, repairing, or rebuilding the destroyed infrastructures (BBC 2014). There is also another added cost in terms of the loss of productivity of individuals who are either directly or indirectly affected by the volcanoes.  

Environmental

In case the mud and ash generated by volcanic activity mix with melting snow or rainwater, lahars could develop (BBC 2014). These are fast-moving mudflows that are known to destroy agricultural land and human settlement. Volcanic explosions contain sulphur dioxide as one of the compounds. Once in the stratosphere, this sulphur dioxide mixes with water to form sulphuric acid. Large acid droplets could hinder the escaping of heat from the earth’s surface, leading to elevated temperatures. In addition, volcanic activity also releases carbon dioxide, a greenhouse gas that causes extreme temperature and weather increase across the globe. This s in turn causes crop failures, health problems, as well as loss of habitat for both flora and fauna. Volcanic eruptions could also develop into a volcanic fog made up of sulphuric-acid droplets, and this might impair air quality.

Evaluation

Nearly half a million people in the world are at potential risk of being affected by volcanic activity owing to their proximity to a volcano (Geoscience Australia 2017). Majority of the areas known to have active volcanoes are also densely populated, a development that is expected to continue in the coming decades. This means that a higher number of people could be predisposed to the social, economic, and environmental effects of volcanic activities. To avoid such an occurrence, it is important that governments collaborate with national and international agencies involved in disaster awareness and mitigation programmes. Investing in volcanic eruption forecasting tools will enable governments to develop volcanic risk mitigation strategies as a means of safeguarding lives, property, and the environment from the negative effects of volcanoes.

 

 

References

BBC (2014). Volcanoes and volcanic eruptions. [Online].

Dobran, F (2012). Volcanic Processes: Mechanisms in Material Transport. New York: Springer.

Geoscience Australia (2017). What causes Volcanoes? [Online].

Gonnermann, H.M & Manga, M (2014). Dynamics of magma ascent in the volcanic conduit. [Online].

Quiñones, N & Shoichet, C.E. (2013). El Salvador's Chaparrastique volcano erupts for first time in 37 years. [Online].

Scientific Americans (2017). What causes a volcano to erupt and how do scientists predict eruptions? [Online].

 

 

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