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fire-fountain A continuous spray of disrupting magma through a vent to form a persistent fountain of molten magma above the vent. The fountain, which may rise to 200 m, is supported either by the hydrostatic pressure of magma in the upper levels of the main volcanic superstructure, or by expanding gas released from the magma during the eruption. Fall-out from the column produces a spatter rampart around the vent and if the accumulation rate is high the molten spatter may coagulate to form a flow of lava (a ‘clastogenic flow’).