The type of magma produced by the volcanoes is closely tied to its plate tectonic setting. Silica-rich magmas tend to erupt more .... Due to the high silica content, rhyolite lava is very viscous, since rhyolite magma is gas rich it can erupt explosively and when the rhyolitic magma reaches the surface, it tends to slowly pile up over vents as thick rounded lava mass. If gas pressure is high enough, rhyolitic magmas erupt explosively to form large calderas.
