Rhyolitic magma has the greatest silica content, with silica making up about 70 percent of the magma. Basaltic and andesitic magma have lower silica contents at 50 percent and 60 percent, respectively.
Magma with a higher silica content is more viscous, meaning it is thicker and doesn't flow as easily. The more explosive volcanic eruptions are caused by this more viscous magma, which means that rhyolitic magma causes the most explosive eruptions.
Rhyolitic magma contributes to the explosive character of siliceous lava flows and lava domes. The Vulcanian and Plinian types of volcanic eruptions feature rhyolitic magma. Eruptions involving rhyolitic magma produce obsidian and pumice rocks, and rhyolitic volcanoes are typically cinder cone volcanoes.