The Birth of a Hawaiian Fissure Eruption
The Birth of a Hawaiian Fissure Eruption
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DOI：
10.1029/2020jb020903
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发表时间：
2021-01-01
影响因子：
3.9
通讯作者：
Patrick, M. R.
中科院分区：
文献类型：
--
作者：
Houghton, B. F.;Tisdale, C. M.;Patrick, M. R.
大多数玄武质的爆炸性喷发是突然加剧的，几乎没有时间记录喷发开始时的过程。一个机会是在2018年夏威夷基拉韦厄下东裂谷带爆发期间，裂缝8（F8）开始活动。F8在四集中爆发。我们在51分钟的时间内录制了28分钟的高清视频，捕捉了5月5日第二次发作的开始。从视频中，我们能够分析以下飞行参数：爆炸的频率和持续时间;喷出物高度;火山碎屑出口速度;飞行中总质量和估计的质量喷发率;以及飞行中总粒度分布。这些视频记录了从最初的脉动放气，通过间隔，但越来越快，离散的爆炸，准持续，不稳定的喷泉过渡。这种转变伴随着蜡强度（质量流量）的F8喷发。我们推断，所有的活动都是由一个组合的上升的耦合混合物的小气泡和熔体，和浮力上升的解耦气栓和/或口袋。这两种类型的并行流动之间的平衡决定了任何时间点喷发活动的确切形式，它们相对贡献的变化推动了我们在F8早期观察到的转变。对基拉韦厄其他夏威夷喷泉的定性观察表明，这种物理模型可能适用于更普遍的情况。这项研究证明了来自高分辨率视频的飞行中参数的价值，它提供了一种快速和高度时间敏感的替代测量的基础上采样的存款postteruption。
Most basaltic explosive eruptions intensify abruptly, allowing little time to document processes at the start of eruption. One opportunity came with the initiation of activity from fissure 8 (F8) during the 2018 eruption on the lower East Rift Zone of Kilauea, Hawaii. F8 erupted in four episodes. We recorded 28 min of high-definition video during a 51-min period, capturing the onset of the second episode on 5 May. From the videos, we were able to analyze the following in-flight parameters: frequency and duration of explosions; ejecta heights; pyroclast exit velocities; in-flight total mass and estimated mass eruption rates; and the in-flight total grain size distributions. The videos record a transition from initial pulsating outgassing, via spaced, but increasingly rapid, discrete explosions, to quasisustained, unsteady fountaining. This transition accompanied waxing intensity (mass flux) of the F8 eruption. We infer that all activity was driven by a combination of the ascent of a coupled mixture of small bubbles and melt, and the buoyant rise of decoupled gas slugs and/or pockets. The balance between these two types of concurrent flow determined the exact form of the eruptive activity at any point in time, and changes to their relative contributions drove the transition we observed at early F8. Qualitative observations of other Hawaiian fountains at Kilauea suggest that this physical model may apply more generally. This study demonstrates the value of in-flight parameters derived from high-resolution videos, which offer a rapid and highly time-sensitive alternative to measurements based on sampling of deposits posteruption.