Volcanoes. Chapter 15. Where do Volcanoes Occur. Divergent Boundaries Convergent Boundaries Hoy Spots Subduction boundaries. Eruptions of Volcanoes. Two factors that determine whether it is explosive or quiet. 1. Is the amount of water vapor and other gases that are trapped in the magma.
Basaltic magma contains less silica is very fluid and produces quiet explosives eruptions.