What factor cause magma to be classified as basaltic, andesitic, or rhyolitic based on what factor?

The three classifications of magma are mainly identified using their silica composition. Basaltic magma has the lowest silica content of 45-55% by weight. This makes it the least viscous and least explosive. Andesitic magma has 55-65%, making it more explosive and viscous. Rhyolitic magma has 65-75% silica, and is the most viscous and catastrophic.