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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Contrasting patterns of vesiculation in low, intermediate, and high Hawaiian fountains: A case study of the 1969 Mauna Ulu eruption
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Contrasting patterns of vesiculation in low, intermediate, and high Hawaiian fountains: A case study of the 1969 Mauna Ulu eruption

机译：低，中和高夏威夷喷泉中的气泡形成对比模式：以1969年莫纳乌鲁火山喷发为例

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Hawaiian-style eruptions, or Hawaiian fountains, typically occur at basaltic volcanoes and are sustained, weakly explosive jets of gas and dominantly coarse, juvenile ejecta (dense spatter to delicate reticulite). Almost the entire range of styles and mass eruption rates within Hawaiian fountaining occurred during twelve fountaining episodes recorded at Mauna Ulu, Kllauea between May and December 1969. Such diversity in intensity and style is controlled during magma ascent by many processes that can be constrained by the size and shape of vesicles in the 1969 pyrodasts. This paper describes pyrodast vesicularity from high, intermediate, and low fountaining episodes with eruption rates from 0.05 to1.3×l0~6m~3h~(-1).As each eruptive episode progressed, magma ascent slowed in and around the vent system, offering extended time for bubbles to grow and coalesce. Late ejected pyrodasts are thus characterized by populations of fewer and larger vesicles with relaxed shapes. This progression continued in the intervals between episodes after termination of fountain activity. The time scale for this process of shallow growth, coalescence and relaxation of bubbles is typically tens of hours. Rims and cores of pumiceous pyrodasts from moderate to high fountaining episodes record a second post-fragmentation form of vesicle maturation. Partially thermally insulated pyrodasts can have internal bubble populations evolve more dynamically with continued growth and coalescence, on a time scale of only minutes, during transport in the fountains. Reticulite, which formed in a short-lived fountain 540 m in height, underwent late, short-lived bubble nucleation followed by rapid growth of a uniform bubble population in a thermally insulated fountain, and quenched at the onset of permeability before significant coalescence. These contrasting patterns of shallow degassing and outgassing were the dominant controls in determining both the form and duration of fountaining episodes at Mauna Ulu, and probably for many other Hawaiian-style eruptions.
机译：夏威夷式火山喷发或夏威夷喷泉通常发生在玄武岩火山上，是持续不断的，微弱的气体喷射流，且主要是粗大的幼体喷射（密集飞溅到细密的网状石）。 1969年5月至12月之间，在夏威夷的喷泉中，几乎所有的样式和喷发速率都发生在12个喷泉事件中，发生在Kllauea的莫纳乌鲁。在岩浆上升过程中，强度和样式的多样性受到许多过程的控制，而这些过程可能受到岩浆上升的限制。 1969年pyrodasts中囊泡的大小和形状。本文描述了高，中，低喷泉事件的吡达司德囊泡，喷发率从0.05至1.3×l0〜6m〜3h〜（-1）。随着每次爆发事件的进行，岩浆上升在通风系统内和周围逐渐减慢，为气泡的生长和聚结提供更长的时间。因此，较晚排出的酒渣酵母的特征在于具有松弛形状的越来越少的囊泡。喷泉活动终止后，发作之间的间隔持续这种进展。此浅层生长，聚结和气泡松弛过程的时间标度通常为数十小时。从中度到高喷泉期发作的霜霉病菌体的边缘和核心记录了囊泡成熟的第二种碎片后形式。在喷泉中运输的过程中，部分绝热的pyrodast可以在仅几分钟的时间范围内，使内部气泡种群随着持续增长和聚结而更加动态地演化。在高度为540 m的短寿命喷泉中形成的网状石经历了晚期，短时气泡成核，随后在隔热喷泉中迅速形成均匀的气泡群，并在渗透率开始之前淬灭，然后显着合并。这些浅层除气和除气的对比模式是确定莫纳乌鲁（Mauna Ulu）喷泉事件的形式和持续时间的主要控制因素，并且可能决定了许多其他夏威夷式喷发。

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