Plate tectonics and geodynamics Essay Example | Topics and Well Written Essays - 500 words

Plate tectonics and geodynamics - Essay Example Therefore, such components will melt at different temperatures and conditions, a process known as partial melting (Morgan & Chen, 1993 p6285). The process of partial melting takes place in the mantle (Best, 2009 p33). The mantle has four basic components; oxygen, silicon, magnesium and iron which have low melting points. Additionally, the upper mantle, which is below the ridges of the ocean, melts, since it comprises of the lithosphere that is brittle and fractures easily under low temperatures (Griffith, 1998 p67). Under normal circumstance, the mantle is formed of a solid rock substance called the peridotite (Annen & Zellmer, 2008 53). Partial melting of the peridotite is caused by the heat generated when rocks slide against one another on the base of the lithosphere, causing frictional kinetic energy at the subduction points (Sinton & Detrick, 1992 p198). This generates heat, which causes some elements of the peridotite with a low melting point to melt (Morgan & Chen, 1993 p6289). Consequently, partial melting occurs on the upper mantle, where the peridotite is melt to form a semi-solid substance called the magma (Best, 2009 p30). When the peridotite is melt, the semi-liquid substance formed is less dense than the materials above it. This is because, at such high temperatures, the magma is in a liquid state, which has a low density compared to the solid materials that are on the earth’s crust (Best, 2009 p28). The less dense magma looks for ways to escape upwards and settle above the solid components above it, due to its low viscosity and low density. Therefore, the hotter liquid substance will rise carrying its temperature with it, until it reaches a point where the temperatures are low. Here, its density is increased through solidification (Griffith, 1998 p70). Oceanic ridges tend to move from one another, creating a channel through which the magma can rise from the mantel of the earth to the earth’s crust