This event is over.
No one anticipated the startling explosivity of the Hunga Tonga eruption in 2022, despite intermittent and increasingly intense precursor eruptions. Why is it so difficult to forecast the magnitude and intensity of eruptions? Some clues are provided by the complex and protracted eruptive sequence that preceded the c. 7700ybp eruption of Mount Mazama, OR. Here preliminary work suggests that (1) early eruptions tapped isolated magma lenses and (2) eruption-induced depressurization triggered both recharge from below and amalgamation of unerupted lenses to produce the climactic event. Importantly, evidence for these processes is preserved in ash from precursor eruptions and suggests that rapid ash analysis could improve eruption forecasts.