<p>Globally, many long-lived stratovolcanoes experience cycles of collapse and regrowth. The influence that these cycles may have on the volcanic system and the subsequent eruptive products are recorded in the deposits of the surrounding ring plains. Taranaki Volcano in New Zealand has experienced at least fourteen major edifice failures during its <i>c</i>. 200 kyr eruptive history and provides a unique opportunity to investigate the impact that collapse/decompression events have on the magmatic system. The Poto and Paetahi tephra formations (27.3–23.1&#xa0;ka) encompass the 27.3&#xa0;ka (5.85 km³) Ngaere and the 24.8&#xa0;ka (7.5 km³) Pungarehu debris-avalanche deposits. Geochemical data show a less evolved composition of pumices produced during the early post-Ngaere collapse units becoming more evolved throughout the late Poto Formation (3.71–5.19 wt.% MgO) and subsequent Paetahi Formation (3.03–4.0 wt.% MgO). Pyroxene rim to matrix equilibrium tests show that only four out of twenty-eight studied tephras contain crystals which may be in equilibrium with the surrounding melt. These yield thermobarometric temperature ranges between 1030 and 1110 °C. Associated plagioclase-matrix hygrometry modelling yielded water contents of 2.8 to 5.8 wt.%. These intensive parameters indicate that eruptions were triggered by hot andesitic magmas moving from depth below Mt. Taranaki. Decompression following the Ngaere collapse allowed denser, more mafic magma to ascend to the surface, incorporating crystals from different levels of the plutonic system on its way. This study highlights the relationship between edifice load and melt density, where a fully loaded edifice is a critical parameter in reducing the ability of dense mafic melt to ascend.</p>