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The cataclysmic basaltic eruption of Mt. Tarawera in 1886 represents a significant cultural and scientific event for New Zealand. This review utilises published and new observations, to reinterpret eruptive parameters encompassing the entirety of the eruption. The ∼17 km eruptive fissure, active for 4+ hours, extends across Mt. Tarawera to the hydrothermally active Waimangu region. Correlating published observations of bed thickness, componentry and microtextures from Mt. Tarawera to new bed descriptions and granulometry for the Rotomahana-Waimangu rift segment allows for a re-assessment of eruption variations along the length of the fissure. Variably thick pyroclastic fall sequences at Mt. Tarawera contrast with the pyroclastic surges and an eruption plume that together deposited the 'Rotomahana Mud' erupted along the Rotomahana-Waimangu segment. Providing insight into pre-eruptive conditions, new mineral chemistry from Mt. Tarawera provides the first constraints on crystallisation pressures (<2 kbar), temperatures (<1100°C), and magmatic water content (<2.8 wt%). Recalculated volumes indicate a bulk eruptive volume of 1.1–1.3 km3, and a juvenile basalt volume of up to 0.67 km3, which then lead to calculated discharge rates of 3.7 × 107–7.8 × 107 kg s−1 for the northern Mt. Tarawera segment of the fissure and 1.4–5.7 × 106 kg s−1 for the Rotomahana segment. [ABSTRACT FROM AUTHOR]

Cenozoic geological evolution of New Zealand centres around the formation of Zealandia, a new continent that became detached from the eastern margin of Gondwana around 105 Ma. Spreading opened the Tasman Sea leaving a fragment of continental lithosphere, largely submerged, in the SW Pacific. Throughout the Cenozoic history, volcanism became an integral part of Zealandia. Continental lithosphere provided the basement for the volcanism, both onshore and offshore. Monogenetic volcanism was common throughout the Cenozoic. The availability of water was ubiquitous through surface water bodies (oceans and lakes) and various other terrestrial hydrous systems provided by the humid temperate climate of Zealandia. Hydrovolcanism, both explosive and non-explosive, has played a significant role in Zealandia's volcanic history resulting in volcano mega- architecture involving edifice geology and volcanic hazards. However, hydrovolcanism has commonly been overlooked in Zealandia's monogenetic volcanism context. Cenozoic monogenetic fields of Zealandia provide a unique laboratory and comparative analogy for other volcanic fields on Earth that are associated with low-lying terrestrial settings or shallow marine environments in a humid temperate climate. [ABSTRACT FROM AUTHOR]