The 1131 CE Te Popo eruption was one of the two largest magnitude eruptions of Taranaki Mounga's most recent eruptive period and followed ~250 years of quiescence. The eruption involved three phases of column development that produced tephra fallout, followed by column collapse events that produced pyroclastic density current and ash deposits reflecting unsteady plumes and an intermittently stable conduit. This study focuses on the lithic clasts ejected during the eruption to understand the role of the shallow conduit and vent in the sub-Plinian eruption's multi-phase dynamics. We show how the conduit was comprised of older edifice lavas and intrusive lithologies that were continuously eroded to achieve more stable geometries during the eruption. Vent and crater excavation dominated early phases, before deeper erosion of intrusive accessory lithics around the fragmentation depth became more prevalent. Lining accumulation both below and above the fragmentation depth occurred continuously during fall phases before being eroded and incorporated into pyroclastic density currents during wall collapse. We propose conduit erosion processes played a significant role in evolving eruption dynamics. These results contrast with lithics ejected during the other large eruption in this period (Burrell Eruption), which occurred between multiple effusive events. The Te Popo episode offers the most likely scenario for re-awakening dynamics of Taranaki, due to the similar length of the pre-eruption repose period (since 1790 CE). • The sub-Plinian Te Popo eruption of Taranaki Mounga followed an extended period of repose (~250 years), similar to the current quiescence since the most recent eruption. • Mineralogy and textures of lithics ejected across the multi-phase eruption reflect conduit establishment through an established volcanic edifice. • Repeated fall episodes separated by column collapse PDCs, ashfall and periods of quiescence reflect unstable conduit walls, possibly due to alteration extent. • Comparing Te Popo lithic clasts to those ejected during the 1655 CE Burrell eruption reveals conduit lining and armouring by the interceding effusive eruptions.
Hoult et al. (Sun,) studied this question.