 These features emerged as intrusive emplacements within sedimentary blocks or as viscous extrusive flows in which the younger flows partially covered the older, lower flows.Geologic evidence suggests that the eruption of the mountain, which occurred at linear vents along regional faults, was a non-explosive event that took place during several flow sequences.Likewise, because of the high viscosity of the dacite, it is likely that the mountain formed in the short period of a few months' time.