Question

why are volcanoes always near river​

Answer 1

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As this low-viscosity magma rises within a volcano to near the surface, water vapor in the form of gas bubbles will quickly come out of solution and cause a brief fountaining effect where bits of lava are spattered around the vent, causing a "spatter cone

Answer 2

As this low-viscosity magma rises within a volcano to near the surface, water vapor in the form of gas bubbles will quickly come out of solution and cause a brief fountaining effect where bits of lava are spattered around the vent, causing a "spatter cone."