Every known type of eruption (Hawaiian, Strombolian, Plinian, subplinian, phreatic, phreatomagmatic, and Vulcanian) has occurred at some point in the range. Cerro Azul itself has experienced phreatic, Strombolian, and Plinian activity in human history. The type of eruption tends to correspond with lava composition. Strombolian eruptions at Llaima, Antuco, Villarrica, and elsewhere have been produced by basaltic to basaltic-andesitic activity. Dacitic to rhyolitic lavas have been linked to subplinian and Plinian eruptions, such as those at Quizapu (1932) and Hudson (1991). Because of this variability, volcanic hazards from Cerro Azul and the surrounding region could come in many different forms. Historical eruptions typically have produced lahars, lava flows, and ashfalls. Lava flows and lahars could wipe out entire cities or towns. Ashfall produced by explosive eruptions could interfere with air traffic. Most threatening of all is the risk of pyroclastic flows or avalanches, which have historically traversed as far as in the region.