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Hazard assessments in monogenetic volcanic fields require estimates of the runout of pyroclastic surges that result from phreatomagmatic explosive activity. Previous assessments used runout distances of 1–4 km, with large cases up to 6 km. Surge deposits at Ubehebe Crater (∼2100 y.b.p., Death Valley, California) have been traced ∼9 km from the crater center, and likely originally extended 1–3 km farther. There is no evidence that the Ubehebe Crater activity was unusually energetic; rather, its distal deposits are better preserved than those at most maar volcanoes because of its young age and the arid environment. Numerical simulations illustrate how low temperatures facilitate long runout of phreatomagmatic surges due to reduced expansion of entrained air compared to hot surges, allowing cool surges to retain higher densities than ambient air. We suggest that hazard assessments for volcanic fields with phreatomagmatic, maar‐forming eruptions should consider runout distances in the range of 10–15 km. Plain Language Summary: Assessments of volcanic hazards in areas prone to small‐volume basaltic volcanoes includes consideration of the lateral extent of devastating pyroclastic surges from eruptions that are caused by magma‐water explosions. Previous assessments considered surge distances up to 6 km, but the deposits from Ubehebe Crater (Death Valley, California, USA) have been traced to 9 km and likely originally extended farther. This was not an unusual eruption, but its deposits are exceptionally preserved due to the arid environment. Pyroclastic surges from magma‐water explosions are likely to be cooler than other volcanic flows, and this facilitates long travel distances and hence far‐reaching potential impacts if the area is inhabited. We suggest that future assessments should consider pyroclastic surge distances of 10–15 km from the vent. Key Points: Hazard assessments in monogenetic volcanic fields have considered pyroclastic surge runout up to 6 km based upon preserved deposits of previous eruptionsSurge deposits from Ubehebe Crater extend to 9 km; this may not be unusual and such surges may have long runout facilitated by their low temperaturesWe suggest that future hazard assessments in monogenetic volcanic fields consider pyroclastic surge runout up to 10–15 km [ABSTRACT FROM AUTHOR]

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]