Abstract The catastrophic explosion of Mount Lamington volcano, Papua New Guinea on January 21, 1951 produced a devastating pyroclastic density current (PDC) that knocked down dense tropical rainforest over an area of 230 km2 and killed approximately 3000 people. We present results of a field reinvestigation of the 1951 PDC deposit combined with an analysis of the available photographs and eyewitness accounts of the eruption first published in the fundamental work of G. A. M. Taylor (1958). We have concluded that the six-days-long pre-climactic activity before the 1951 eruption (which included felt local seismicity, frequent ash-laden explosions of vulcanian type, bulging of the volcano slope accompanied with landslides) was associated with shallow-level intrusion of a highly viscous magma body (cryptodome/dome) of andesitic composition with a volume of approximately 0.01 km3. This intrusion destabilized Mount Lamington's prehistoric intra-crater lava dome. On January 21 the destabilized dome gravitationally collapsed and produced a relatively small-volume debris avalanche, the deposit of which was not recognized during Taylor's original investigation. The debris avalanche had a volume of approximately 0.02–0.04 km3, travelled a distance (L) of 8.5 km and had the ratio of vertical drop (H) to runout (L) of 0.14. The edifice collapse decompressed the intruding cryptodome and triggered its explosive fragmentation. Photographs of the climactic explosion show that the eruptive cloud initially rose vertically but subsequently collapsed upon the terrain around the vent, and formed a PDC which flowed radially outward. The enhanced northward propagation of the PDC to a maximum distance of 13 km reveals that the northern breach in the ancient crater's high walls influenced the distribution of the deposit. In the studied NE-N-NW sector of the devastated area, in the zone proximal to the volcano, the PDC emplaced a normally graded layer of coarse ash and lapilli mixed in the base with picked-up soil and plant fragments. The layer gradually becomes thinner and finer-grained with distance from the volcano. The PDC deposit has a volume of approximately 0.025 km3 and consists of approximately 80% juvenile rock fragments derived from the explosively fragmented cryptodome. The remaining 20% consists of accidental clasts derived from the old volcanic edifice. The juvenile material is crystal-rich andesite with a unimodal vesicularity distribution (4 to 36%). The reconstructed eruption sequence, the PDC tree blowdown pattern and characteristics of the PDC deposit are similar to those of catastrophic laterally-directed blasts of volcanoes Bezymianny in 1956, Mount St.Helens in 1980, and Soufriere Hills, Montserrat in 1997. In contrast to the cases of these “classic” lateral blasts, the blast cloud of Lamington was initially vertically-directed before collapsing to produce a PDC. We speculate that the climactic explosion of Mount Lamington was initially vertical because the rupture surface of the triggering sector collapse intersected the apex of the intruding cryptodome (it exposed a subhorizontal surface of the cryptodome apex), while at Bezymianny, Mount St.Helens, and Soufriere Hills the rupture intersected the main body of the cryptodome/dome, and exposed their steeply inclined surfaces.

中文翻译：

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1951 年巴布亚新几内亚拉明顿山的喷发：由小规模建筑物故障引发的毁灭性定向爆炸

摘要 1951 年 1 月 21 日，巴布亚新几内亚拉明顿火山发生灾难性爆炸，产生了毁灭性的火山碎屑密度流 (PDC)，摧毁了 230 平方公里的茂密热带雨林，造成约 3000 人死亡。我们展示了对 1951 年 PDC 矿床进行实地再调查的结果，并结合了对首次发表在 GAM Taylor (1958) 的基础工作中的喷发照片和目击者描述的分析。我们得出的结论是，在 1951 年火山喷发之前的 6 天前高潮活动（包括有感觉的局部地震活动、频繁的火山类型火山灰爆炸、伴随山体滑坡的火山斜坡膨胀）与体积约为 0.01 平方公里的安山岩组成的高粘性岩浆体（隐穹丘/穹窿）的浅层侵入有关。这次入侵破坏了拉明顿山史前火山口内熔岩穹顶的稳定。1 月 21 日，不稳定的穹顶在重力作用下坍塌，并产生了体积相对较小的碎片雪崩，在泰勒最初的调查中并未发现其沉积物。碎片雪崩的体积约为 0.02-0.04 平方公里，行进距离 (L) 为 8.5 公里，垂直落差 (H) 与跳动 (L) 之比为 0.14。大厦倒塌解压了侵入的密穹顶并引发了它的爆炸性碎裂。高潮期爆炸的照片显示，喷发云最初垂直上升，但随后在喷口周围的地形上坍塌，并形成径向向外流动的 PDC。PDC 向北传播的增强最大距离为 13 公里，这表明古陨石坑高壁的北裂口影响了沉积物的分布。在受灾地区所研究的 NE-N-NW 部分，在靠近火山的区域，PDC 放置了一个正常分级的粗灰和火山灰层，混合在基部与拾取的土壤和植物碎片。随着离火山的距离越来越远，该层逐渐变得更薄和更细。PDC 存款的体积约为 0。025 平方公里，由大约 80% 的年轻岩石碎片组成，这些碎片来自爆炸性破碎的隐穹顶。剩下的 20% 由来自古老火山建筑物的意外碎屑组成。幼年材料是富含晶体的安山岩，具有单峰气泡分布（4% 至 36%）。重建的喷发序列、PDC 树排污模式和 PDC 矿床的特征类似于 1956 年 Bezymianny 火山、1980 年圣海伦火山和 1997 年蒙特塞拉特 Soufriere Hills 火山的灾难性横向爆炸。在这些“经典”横向爆炸的情况下，Lamington 的爆炸云最初是垂直定向的，然后坍塌以产生 PDC。