When magma is heated within the mantle, the process typically involves convection currents. Here's how it works:
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Heating of Magma: As the magma in the mantle gets heated, it becomes less dense. This is primarily because the heat causes the materials within the magma to expand, leading to a decrease in density.
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Movement of Magma: Due to the decrease in density, the heated magma tends to rise toward the earth's surface. This upward movement is part of the convection currents, where hot magma ascends, cools, and then eventually sinks back down.
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Cooling and Density Changes: As the magma rises, it may cool slightly, which can increase its density again, but generally, as long as the temperature remains higher than the surrounding cooler mantle, it will continue to rise.
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Continued Convection: Once it reaches a certain point or if it is trapped below the crust, it can either pool in magma chambers or cause volcanic activity if it makes its way through fractures in the crust.
In summary, when magma is heated within the mantle, it rises due to decreased density. Convection currents play a key role in facilitating this movement, contributing to various geological processes such as the formation of igneous rocks and volcanic eruptions.