Lava, fountainingVolcanic eruptions are driven by expanding gas released from the magma as the confi
Lava, fountainingVolcanic eruptions are driven by expanding gas released from the magma as the confining pressure decreases when it approaches the surface. Depending on the consistency of the lava (how thick and viscous it is, various types of eruption result. Basalt has less silica and is more fluid (since the silica tetrahedra form polymers that thickens the molten rock), while rhyolite at the other end of the silica enrichment scale tends to move like slow toothpaste, but explode viciously when the pent up pressure from exsolved gas breaks through the confining rock. These are relatively fluid basaltic lava fountains, spouting out of last year’s fissure eruption on Iceland and then flowing towards the sea like rivers.LozImage credit: Orvar Atli Porgeirsson / Barcroft Media -- source link
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