EARTH SCIENCE
VOLCANOES
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Pressure is released making the melting point of the mantle rock lower.
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Water lowers the melting point of the mantle rock
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The temperature of the rock is increased.
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Pressure on the mantle rock is increased.
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Detailed explanation-1: -At convergent boundaries magma is formed where water from a subducting plate acts as a flux to lower the melting temperature of the adjacent mantle rock. At divergent boundaries magma forms because of decompression melting. Decompression melting also takes place within a mantle plume.
Detailed explanation-2: -Why does melting occur at convergent plate boundaries? The subducting plate heats up as it sinks into the mantle. Also, water is mixed in with the sediments lying on top of the subducting plate. This water lowers the melting point of the mantle material, which increases melting.
Detailed explanation-3: -At a convergent plate boundary, one plate dives or “subducts” beneath the other, resulting in a variety of earthquakes and a line of volcanoes on the overriding plate.
Detailed explanation-4: -When the plates move apart, the pressure on the rocks in the upper mantle just below the plate boundary drops. The pressure drop lowers the rock’s melting temperature, and, because these rocks are already hot, they melt, forming magma. At convergent plate boundaries two plates move toward each other.