Magma originates from the Earth's mantle, which lies beneath the Earth's crust and above the outer core. It is formed under conditions of high temperature and pressure. The process of magma generation involves the melting of rocks, which can occur due to several factors:
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Increase in Temperature: As depth increases, temperature rises. When rocks reach their melting point, they begin to melt and form magma.
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Decrease in Pressure: When rocks in the mantle rise towards the surface, the pressure decreases. This reduction in pressure can lower the melting point of rocks, allowing them to melt and form magma (a process known as decompression melting).
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Addition of Water: The presence of water and other volatiles can lower the melting point of rocks. Subduction zones, where one tectonic plate is forced beneath another, often provide the right conditions for this process, causing magma to form when water is released from the descending plate.
Once formed, magma can rise through the Earth's crust due to its lower density compared to the surrounding rock. If it reaches the surface, it can erupt as lava, leading to volcanic activity. If it cools and solidifies underground, it forms igneous rock.
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