What determines the violence of an eruption?. Composition of the magma determine the “violence” or explosiveness of a volcanic eruption. Composition of Magma . Temperature: most rock melt at 800-1200C
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Composition of the magma
determine the “violence” or explosiveness of a volcanic eruption
As amount increases, exclusivity increases
The above three factors control
the viscosity of magma
Think of Syrup & Water
Viscosity – dependent on both silica content and temperature.
• Temperature - Hotter magmas are less viscous
(Compare difference between cold & hot syrup)
• Composition - Silica (SiO 2 ) content
More silica, > viscosity : (thick & stick) gases trapped, explosive eruptions (Rhyolitic Lava)
Less silica, < viscosity : (thin & runny) flow easily, nonexplosive eruptions (Basaltic Lava )