Which mechanism causes felsic magma to exhibit higher explosivity during volcanic eruptions?

💡 Explanation

When felsic magma, rich in silica, ascends, its high viscosity hinders the escape of dissolved gases; this causes increasing pressure until explosive decompression occurs due to bubble nucleation. Therefore, higher viscosity determines explosivity, rather than lower solubility, crystallization or reduced water content requiring different magma properties.

• Which risk increases when rapid urbanization constricts a river channel with natural levees?
• Which change arises if arid region soils experience increased rainfall?
• Which risk increases when a large coastal levee system experiences prolonged saltwater intrusion?
• Which risk increases when rapid levee construction uses poorly compacted fill material on a floodplain lacking vegetation?
• Which mechanism significantly reduces river flow velocity immediately adjacent to a natural levee?
• Along subduction zones, which mechanism primarily controls variability in explosive volcanic eruption intensity?