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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Transport and sedimentation dynamics of transitional explosive eruption columns: The example of the 800 BP Quilotoa plinian eruption (Ecuador)
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Transport and sedimentation dynamics of transitional explosive eruption columns: The example of the 800 BP Quilotoa plinian eruption (Ecuador)

机译：过渡炸药爆发柱的输运和沉积动力学：以800 BP Quilotoa plinian爆发为例（厄瓜多尔）

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摘要

Impact of large-scale explosive eruptions largely depends on the dynamics of transport, dispersal and deposition of ash by the convective system. In fully convective eruptive columns, ejected gases and particles emitted at the vent are vertically injected into the atmosphere by a narrow, buoyant column and then dispersed by atmosphere dynamics on a regional scale. In fully collapsing explosive eruptions, ash partly generated by secondary fragmentation is carried and dispersed by broad co-ignimbrite columns ascending above pyroclastic currents. In this paper, we investigate the transport and dispersion dynamics of ash and lapillis during a transitional plinian eruption in which both plinian and co-ignimbrite columns coexisted and interacted. The 800 BP eruptive cycle of Quilotoa volcano (Ecuador) produced a well-exposed tephra sequence. Our study shows that the sequence was accumulated by a variety of eruptive dynamics, ranging from early small phreatic explosions, to sustained magmatic plinian eruptions, to late phreatomagmatic explosive pulses. The eruptive style of the main 800 BP plinian eruption (U1) progressively evolved from an early fully convective column (plinian fall bed), to a late fully collapsing fountain (dense density currents) passing through an intermediate transitional eruptive phase (fall+syn-plinian dilute density currents). In the transitional U1 regime, height of the convective plinian column and volume and runout of the contemporaneous pyroclastic density currents generated by partial collapses were inversely correlated. The convective system originated from merging of co-plinian and co-surge contributions. This hybrid column dispersed a bimodal lapilli and ash-fall bed whose grain size markedly differs from that of classic fall deposits accumulated by fully convective plinian columns. Sedimentological analysis suggests that ash dispersion during transitional eruptions is affected by early aggregation of dry particle clusters.
机译：大规模爆炸爆发的影响在很大程度上取决于对流系统对灰分的传输，扩散和沉积的动力学。在完全对流的喷发塔中，排放口处排放的气体和颗粒通过狭窄的浮力塔垂直注入大气，然后通过大气动力学在区域范围内扩散。在完全坍塌的爆炸喷发中，部分由二次破碎产生的灰烬被宽泛的共燃柱携带并散布，这些柱子在火碎屑流上方上升。在本文中，我们研究了在过渡的普林期喷发中灰烬和青金石的迁移和扩散动力学，在该过渡期的普林期和共生石柱共存并相互作用。 Quilotoa火山（厄瓜多尔）的800 BP爆发周期产生了暴露良好的特非拉序列。我们的研究表明，该序列是由各种喷发动力积累的，从早期的小型潜水爆炸到持续的岩浆性普利尼山喷发，再到晚期的岩浆爆发脉冲。主要的800 BP普利尼山喷发（U1）的喷发样式逐渐从早期的完全对流柱（普利尼陷落床）演变为经过中间过渡喷发阶段（fall + syn-普林尼稀密度电流）。在过渡的U1阶段，对流夹层柱的高度与部分塌陷产生的同时热碎屑密度流的体积和跳动成反比。对流系统起源于共普林尼和共浪涌贡献的合并。这种混合柱分散了双峰拉皮利和灰烬沉降床，其粒径明显不同于完全对流的普林尼雅柱所累积的经典秋天沉积物。沉积学分析表明，过渡喷发过程中的灰分扩散受到干颗粒团簇的早期聚集的影响。

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