Analysis of Volcanoes


Introduction

A volcano is considered to be an open surface, which is found on the surface of the earth and it allows the hot molten lava to flow from the surface. Generally, volcanoes are found on divergent or convergent tectonic plates (American Museum of Natural History, 2006). For instance, the Mid-Atlantic Ridge is because of the divergent tectonic plates. On the other hand, Pacific Ring of Fire is because of the tectonic plates that are convergent in nature (American Museum of Natural History, 2006). The aim of this paper is to analyse the different types of volcanoes in the lights of broad and diverse academic resources.

Overview

Volcanoes are considered to be holes, gaps or vents that are present in the crust of the Earth. They are formed because of upward movement of the molten lava that comes on the surface of the earth (Marti and Ernst, 2005). The molten lava or magma is assembled in a cavity, which is found beneath the surface of the earth. As the pressure increases at such a rate that it goes upwards by means of fissures or gaps and a channel to the top most layer of the earth is created. Magma contains hot gases, which make attempts to escape but are entrapped inside the magma (Cambridge Encyclopedia, 2010). As the pressure crosses its limit, the surface of the earth bulges and hence, the volcano erupts. Research suggests that the volcano has the tendency to erupt several times during its lifetime. The continuous eruptions gradually develop itself into a cone shaped mountain. The center of the cone shaped mountain has an opening, which is known as the central vent. There is a possibility that smaller openings may be present (CNN World, 2009).

“In many volcanoes there is a bowl shaped crater at the top of the central vent. Under the volcano there is a large magma chamber where the magma is”(Marti and Ernst, 2005). The powerful eruption depends on the quantity of gas found in the magma. This means that higher the concentration of gases, higher would be the explosion and vice versa. The magma comes out from the volcano as lava, which “settles on the sides of the volcanic mountain and cools forming a hard crust of brand spankin new earth. Depending on how much lava and tephra build up different types of volcanoes can be formed” (Marti and Ernst, 2005). The largest volcano can be found in the island of Hawaii. The total height of Mauna Kea above sea level is about thirty thousand feet. This island has “several coalescing volcanoes including Mauna Loa, Mauna Kea and Kilauea. Mauna Loa alone has an estimated volume of 40 000km” (Global Volcanism Network, 1993).

Types of Volcanoes

Volcanoes are considered to be holes, gaps or vents that are present in the crust of the Earth. They are formed because of upward movement of the molten lava that comes on the surface of the earth. The molten lava or magma is assembled in a cavity, which is found beneath the surface of the earth. As the pressure increases at such a rate that it goes upwards by means of fissures or gaps and a channel to the top most layer of the earth is created. Magma contains hot gases, which make attempts to escape but are entrapped inside the magma (Macdonald and Agatin, 1970). As the pressure crosses its limit, the surface of the earth bulges and hence, the volcano erupts. Research suggests that the volcano has the tendency to erupt several times during its lifetime. Following are the most common types of volcanoes:

Cinder Cone Volcanoes

Cinder Cone Volcanoes are considered to be simple volcanoes. They form when the particles of the lava explode from the opening of the volcano. The lava blows into the air and its cooled pieces return and settle all over the vent. Slowly and gradually, the volcano develops a circular of oval shape in the form of a cone (Keller, 2010). At the top, it has crater, which is in bowl shape. The height of this type of volcano is generally not larger than one thousand feet. This type of volcano is represents the shape of hill, which is steep and conical. The fragments of the volcano are known to gather all around the volcanic vent (Macdonald and Agatin, 1970). The fragments of the rock are referred to be as cinders and are glassy. They are known to have several frozen gas bubbles. The material of the cinder cones is pyroclastic.

Several of these volcanoes have a crater, which is bowled shape. “ Lava flows are usually erupted by cinder cones, either through a breach on one side of the crater or from a vent located on a flank”  (Marti and Ernst, 2005).  Once the crater reaches its peak limit, the walls left behind assume the shape of an amphitheatre around the opening. These types of volcanoes are present on the sides of stratovolcanoes, calderas and shield volcanoes. According to geologists, Mauna Kea, which is considered to be shield volcano, has more than ninety cinder cones. Paricutin is known to be one of the most popular cinder cone volcanos and its height is about 424 meters. This Cinder Cone is found in Mexico. Nicaragua is the home of one the most active Cinder Cone, which is known as Cerro Negro( Griggs, 2006).

Composite Volcanoes

Stratovolcano or composite volcano is known to be a conical shaped volcano, which is tall. It is made from several different layers of solidified and cooled lava, pumice, volcanic ash and tephra. The main attributes of these volcanoes include their profile that is steep and recurring, unstable eruptions. “The lava that flows from stratovolcanoes typically cools and hardens before spreading far due to high viscosity”(Keller, 2010).  The nature of the magma of the high viscous lava is felsic, with high contents of silica and insignificant amounts of mafic magma. These volcanoes are known as composite volcanoes “of their composite layered structure built up from sequential outpourings of eruptive materials” (Keller, 2010). The most popular composite volcanoes include Mount Vesuvius and Karakatoa.

Shield Volcano

A shield volcano is considered the third type of volcano, which is created because of the flow of fluid lava. These types of volcanoes got their name from their massive size and low profile. The shape of this volcano resembles the shield of a warrior. These volcanoes are the product of eruption of fluid lava, which has the capability to travel at an accelerated rate when it is erupted (Seach, 2008). Consequently, the lava assembles into wide and expansive sheets, which slowly and steadily assume the shape of the shield. The nature of fluid lava, which leads to the formation of shield volcanoes, is considered to be basaltic. The eruptions of these volcanoes have been assigned a special name, which is the Hawaiian eruptions, as they are commonly found in Hawaii (Watson, 1997). The Hawaiian eruptions are the product of vociferous and effusive release of fluid lavas. Because of their fluid nature, they have ability to reach a higher distance as compared to other types of lava and therefore, they spread out evenly and assume the shape of shield. The volcanic activity of shield volcano is continuous and common. Gradually and slowly, it creates sprinkled cones at the sites of eruption. “A hallmark of shield volcanism is lava tubes, cave-like volcanic straights that are formed by the hardening of overlaying lava”(Marti and Ernst, 2005). The most popular shield volcanoes include Mauna Loa and Mauna Kea.

Lava Domes

Lava domes are considered to those types of volcanoes, which are created from highly viscous lava, which has the ability to cover a great distance (Macdonald and Agatin, 1970). The magma accumulates at the top, one over the other and the around. Slowly and steadily, the lava expands and assumes the shape of the dome. These types of volcanoes can explode violently.

Fissure Vent

A fissure vent is considered to be that type of volcano, which is linear. The lava that comes out from it is the not the product of any explosive activity. The vent is wide and has the ability to create lava channels as well as flood basalts.  Because of its linear nature, it is difficult to detect this type of volcano from ground as its surface is flat. It may appear to be a crack or fissure on the surface of the earth. It may also be found on the floor of the ocean. Narrow fissures can be filled in with lava that hardens. As erosion removes its surroundings, the lava mass could stand above the surface as a dyke. The dykes that feed fissures reach the surface from depths of a few kilometers (Marti and Ernst, 2005).  These fissure vents are commonly found in Iceland and in Africa. Frequently, they are found in shield volcanoes. In Iceland, these vents are found in the rift zones, on the divergent plates.

Submarine Volcanoes

Submarine Volcanoes are the volcanoes that are commonly found on the surface of the ocean. They may be active or dormant. They are mostly found at higher depths and the weight of the water is great in that area. Because of the significant weight of the water, their ability to produce gas and steam is hindered. Research suggests that “they can be detected by hydrophones and discoloration of water because of volcanic gases” (Macdonald and Agatin, 1970).  In certain cases, there is a possibility that pumice rafts may bee seen.

Subglacial volcanoes

These are the types of volcanoes, which are formed beneath the ice caps. They are composed of flat lava. The flat lava is known to flow from the top of pillow lavas and palagonite (Macdonald and Agatin, 1970). The lava found at the top is removed as soon as the icecap melts. Thus, a flat topped mountain is seen. These types of volcanoes are also known as TableMountains or mobergs. They are most commonly found in British Columbia (Marti and Ernst, 2005).

Mud volcanoes and Cryptodomes

Mud volcanoes are also known as mud domes and they are the product of liquids and gases that are secreted by the earth. Cryptodomes are those types of volcanoes which are created because of the bulging of the lava after it explodes. “The 1980 eruption of Mount St. Helens was an example. Lava was under great pressure and forced a bulge in the mountain, which was unstable and slid down the north side”) (Marti and Ernst, 2005).

Conclusion

A volcano is considered to be an open surface, which is found on the surface of the earth and it allows the hot molten lava to flow from the surface. Cinder Cone Volcanoes are considered to be simple volcanoes. Stratovolcano or composite volcano is known to be a conical shaped volcano, which is tall. A shield volcano is considered the third type of volcano, which is created because of the flow of fluid lava. Lava domes are considered to those types of volcanoes, which are created from highly viscous lava, which has the ability to cover a great distance. Other types of volcanoes include fissure vents, mud volcanoes, cryptodomes, subglacial volcanoes and submarine volcanoes.

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