Answer
A typical lava dome is composed of highly viscous lava, often of rhyolitic or andesitic composition. This lava is rich in silica, making it thick and sticky. Lava domes form when viscous magma is slowly extruded from a volcano, piling up and solidifying near the vent. The resulting dome is typically composed of compacted and solidified lava.
On the other hand, a typical fissure eruption is characterized by the eruption of basaltic lava. Basaltic lava has low viscosity and is more fluid compared to rhyolitic or andesitic lava. It is rich in iron and magnesium and contains less silica. Fissure eruptions occur when molten lava is released through long cracks or fissures in the Earth's crust, resulting in the outpouring of large volumes of relatively low-viscosity lava. This lava spreads out in thin sheets or flows, creating extensive lava fields or flood basalts.
In summary, lava domes are composed of highly viscous and silica-rich lava, while fissure eruptions involve the eruption of basaltic lava with lower viscosity and lower silica content.
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