We begin by describing phreatic eruptions that initiated large magmatic eruptions. Some of the most powerful eruptions ever recorded have been phreatic explosions resulting from the rise of magma into the water-soaked upper parts of volcanoes, as at Arenal, Bezymianny, and Shiveluch, next to be described, and in each case inclined blasts of immense energy blew out great volumes of lithic debris and were followed by purely magmatic explosions.