Rock Cycle

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Essay Question:Describe and explain how rock cycle operates. How do rocks metamorphose at destructive plate boundary?

Rock cycle is a cycle that describes how rocks are transformed. Igneous rock can change into sedimentary rock or metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock. Metamorphic rock can change into igneous or sedimentary rock. Besides, metamorphism at the destructive plate boundaries creates different characteristics of rocks.

Operation of the rock cycle
The Rock Cycle

Rock cycle is the cycle of rock transformation which affects all rocks. The cycle involves all parts of the crust.

When the rocks are subducted into the asthenosphere due to compression, the rocks melt into magma. The melting of rocks intensifies the pressure in the asthenosphere. Cracks develop. When cracks extend downward and reach the magma, the pressure of magma is released. Magma then extrudes out of the crust along the cracks to the earth’s surface. It results in vulcanicity. Magma cools and solidifies to form igneous rocks when rises nearer to or above the earth surface. During the cooling process, crystallization takes place in magma or lava forming minerals. The accumulation of minerals forms igneous rock.

When the processes of vulcanicity, cooling and solidification of magma take place in the crust, the rocks formed are called intrusive igneous rocks. Igneous rocks that are formed deep underground are called plutonic rocks and hypabyssal rocks are formed at intermediate depth below the earth surface. When the processes of vulcanicity, cooling and solidification of lava take place on the earth surface, extrusive igneous or volcanic rocks are formed.

Any rocks exposed on the land surface are subject to exogenetic processes. They include commonly denudation (weathering, erosion, transportation) and deposition. With the help of denudation agents, rocks are broken down and brought downslope....
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