An eruption is classified as an explosive volcanic eruption based on the amount of which mineral found in the magma?

An eruption is classified as explosive primarily based on the amount of silica (SiO2) found in the magma. Higher silica content increases the viscosity of the magma, preventing gas from escaping easily, which leads to the buildup of pressure and ultimately results in explosive eruptions. Conversely, magma with lower silica content tends to be less viscous and allows gases to escape more readily, resulting in less explosive activity.