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Volcanoes at destructive and constructive margins

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Introduction

Volcanic impacts are more hazardous near destructive margins than constructive ones. Discuss. I agree that volcanic impacts are more hazardous near destructive margins than constructive ones. Destructive margins occur where continental and oceanic plates converge together or oceanic and oceanic plates converge together. For the former, the continental crust has a rock density much lower than the oceanic crust. As these two plates meet the oceanic crust is submerged underneath the continental crust, as it is denser. This causes a subduction zone to form where deep sea trenches result. As the oceanic plate is submerged, it begins to melt due to increased heat and friction. The melting of the plate results in magma building up, which eventually rises up to the surface as volcanoes. As for the later, the denser plate will be subducted and some of the magma will rise through fractures in oceanic crusts and pour onto ocean floor, forming undersea volcanoes. ...read more.

Middle

The composite volcanoes are typically steep-sided, symmetrical cones of large dimension built of alternating layers of lava flows, volcanic ash, and cinders. As lava is acidic, the lava is thick and sticky and this viscosity of the lava does not allow trapping gas to escape. Additionally, the lava solidifies in the central pipe, blocking the passage and these built up the pressure in the volcano. Therefore when the volcano erupts, there will be violent explosion as ash and act as a medium of transportation for lava and allow the lava to flow over them quickly. Also, pyroclastic materials will also be poured out. The shield volcano is a gently sloping volcano that is flat near the top and is built entirely by basic lava. By its basic nature, the lava is more fluid and it flows faster than the lava in the composite volcano before solidifying. However, unlike the composite volcano, there will be no explosion when the volcano erupts at a constructive margin, as there is no pressure and thus gas can escape easily through the less viscous lava, and very little pyroclastic material or none is found within the volcano. ...read more.

Conclusion

Certainly, there will be volcanoes that have not grown and are underwater; their eruptions might be invisible on sea surface and will not affect any human beings. On the other hand, volcanoes at destructive margins are usually located on land, but there are some exceptions that are also located on sea. Those that are on land are very hazardous as many people stay around the volcano because the volcano lava can form fertile land for agriculture uses. Thus, when the volcano erupts, the volcanic impacts are disastrous and hazardous as many people and their homes are affected. One example of such cases is the Mount Pinatubo in The Philippines. The human impacts of the disaster are staggering. In addition to the up to 800 people who lost their lives, there was almost one half of a billion dollars in property and economic damage. In conclusion, the volcanic impacts at destructive margins are more hazardous than those at constructive ones. Composite volcanoes, at destructive margins, are more explosive than shield volcanoes, at constructive margins, because composite volcanoes contain pyroclastic flows and are mostly located on land. ...read more.

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