In the AD 1640 eruption, the injected mafic magma is
inferred to have ascended as a dike into a silicic chamber while mingling;
the mafic material was erupted first. In the AD1694 eruption,
gray pumice occurs in addition to the other three types of ejecta and
this has whole-rock compositions intermediate between those of the
white pumice and scoria. In addition, the gray pumice contains
phenocrysts with reverse zonation, suggesting that it is a product of
mixing between the end-member magmas.