Rangitoto, the youngest and largest volcano in New Zealand’s Auckland Volcanic Field, offers insights into polygenetic behavior within a field of monogenetic basaltic volcanoes. My research examined the eruptive history and magma ascent dynamics of Rangitoto by analyzing Fe-Mg diffusion in olivine crystals from its summit and lower lava field. Two distinct magma batches, separated by ~50 years, indicate a complex eruption history. Using back-scattered electron (BSE) imaging and diffusion modeling techniques, I analyzed zoned olivine crystals to reconstruct magma ascent durations. Normally zoned olivines in basal lavas recorded two cooling events. Summit samples revealed reverse-zoned olivines with Mg-rich rims, indicative of rapid cooling over 1–20 days, likely triggered by a mafic magma injection. This injection rejuvenated the magmatic system, forming the central scoria cone and facilitating the ascent of Fe-rich magma to create the basal lavas. These findings have significant implications for assessing future volcanic hazards in Auckland, one of New Zealand’s largest cities.

Tenerife, a volcanic island located off the northwestern coast of Africa has a complex history, with a wide range of magma compositions and diverse eruption styles from effusive to Plinian eruptions producing pyroclastic density currents. While explosive, ignimbrite forming events are well documented, significant gaps in the eruption record remain. Throughout this 4 week internship, we refined eruptive record through detailed stratigraphic logging and reconnaissance studies, particularly within the lower Diego Hernández Group exposed along the Las Cañadas Caldera wall. This work provides new insight into the frequency and distribution of explosive eruptions, improves hazard assessments for future volcanic activity, and contributes to GeoTenerife's Volcanic Readiness project.