Steam‐driven eruptions are explosive events that are fueled by pressurized water and steam trapped within rock and sediments. We show how rock properties modulate explosion size, dynamics, and hazard footprint based on examples from Lake Okaro (New Zealand). Laboratory decompression experiments demonstrate that fragmentation of strong/unaltered host rocks comes with a high energy cost (∼10%–11% of bulk explosion energy). Consequently a low energy fraction (∼7%–8%) remains for kinetic energy and thus particle ejection. In contrast, disaggregation of unconsolidated sediments requires little energy (<2%–7%), allowing higher outputs of kinetic energy (22%–25%), and more efficient debris dispersion. Experimental estimates of bulk explosive energies are consistent with both field observations and empirical models applied to Lake Okaro crater dimensions. This integration of experimental methods, field observations, and empirical modeling underscores the dominant role of alteration state and host rock lithology when estimating crater‐forming and ballistic hazards in volcanic/geothermal areas.

中文翻译：

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宿主岩石的可变性推动了蒸汽驱动喷发的多样性

蒸汽驱动的爆发是爆炸性事件，由压缩水和截留在岩石和沉积物中的蒸汽推动。我们以Okaro湖（新西兰）为例，说明岩石特性如何调节爆炸的大小，动力和危害足迹。实验室减压实验表明，坚硬/未改变的主体岩石碎裂会带来高昂的能源成本（约占整体爆炸能量的10％–11％）。因此，动能和粒子射出的能量分数仍然较低（约7％–8％）。相反，未固结沉积物的分解所需的能量很少（<2％–7％），因此动能输出较高（22％–25％），并且碎片分散效率更高。大块爆炸能量的实验估计与应用于Okaro湖火山口尺寸的实地观察和经验模型一致。在估算火山/地热地区的火山口形成和弹道危害时，这种实验方法，现场观察和经验模型的整合突显了蚀变状态和宿主岩石岩性的主要作用。