Start me up: The relationship between volcanic eruption characteristics and eruption initiation mechanisms

Understanding the processes that initiate volcanic eruptions after periods of quiescence are of paramount importance to interpreting volcano monitoring signals and mitigating volcanic hazards. However, studies of eruption initiation mechanisms are rarely systematically applied to high-risk volcanoes. Studies of erupted materials provide important insight into eruption initiation, as they provide direct insight into the physical and chemical changes that occur in magma reservoirs prior to eruptions. Petrologic and geochemical studies can also constrain the timing of processes involved in eruption initiation, and the time that might be expected to elapse between remote detection of increased activity and eventual eruption. A compilation and analysis of literature data shows that petrological evidence identifies four distinct processes of eruption initiation: mafic recharge (intrusion of mafic magma into a felsic magma storage region), mafic rejuvenation (intrusion of mafic magma into a mafic magma storage region), felsic rejuvenation (intrusion of felsic magma into a felsic magma storage region) and volatile accumulation. Other mechanisms such as roof collapse or increasing buoyant forces may also initiate eruptions but leave little petrological record in erupted material. There are also statistical differences in the composition, volume, style, and timescales between eruptions initiated by these different mechanisms, and these suggest that increasing eruption volumes, longer initiation timescales, more felsic compositions, and more explosive eruption styles occur going from mafic rejuvenation to mafic recharge, felsic rejuvenation and volatile accumulation. Knowledge of the processes that initiate eruptions at a given volcanic system may thus have significant predictive power.