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Understanding Volcanoes and their Types Essay

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Understanding volcanoes require our understanding of planet Earth’s structure. Earth is a ball of rocks divided into four layers; crust, mantle, outer core and inner core. The Crust is the outermost layer. It comprised of continental and oceanic crust. The second layer is the mantle and it makes up about 80% of the Earth’s total volume. The outer core is liquid consisting of iron and nickel and it is the third layer. The Forth layer, inner core is the solid iron and nickel alloy. The temperature and density of these layers differs. Inner core has the highest temperature and density with the crust having the lowest temperature and density in comparison. The extreme pressure and temperature within the earth causes the hot magma (also known …show more content…

Their eruptions are mixtures of hot stream, ash, rock and dust (pyroclastic flow) rather than lava flow (BBC, n.d.). Composite volcano has crater at the summit which have one or more vents. Its conduit system through is an essential feature as it contribute to the size of the volcano as lava, cinders, bombs and ash are added to its slope. In addition, silica content has direct effect on the fluidity of the magma. An increase in silica concentration results in an increase in magma resistance to flow (viscosity). Andesite magma which have high content of silica compared to basalt magma make up most of the composite volcanoes fragmental materials. This silica-and volatile-rich magma is what separate composite volcanoes from shield volcanoes. Although, andesite magma dominate fragmental debris, some magma intrudes the cones such as sills or dikes. Due to this multiple intrusions, the strength of the structural framework is obtained and therefore composite volcanoes stand higher than those composed solely of the fragment materials. Sigurdsson (2000) observed that there are at least two factors that promote the formation of composite volcanoes. First the composition of erupted magma and second the eruption style. Magma composition varies depending the site of eruption. Magma Eruptions at convergent plate are results of differentiation and volatile concentrations. The style of eruptions is

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