Magmatic overpressures, volatile exsolution and potential explosivity of fissure eruptions inferred via dike aspect ratios
Magmatic overpressures, volatile exsolution and potential explosivity of fissure eruptions inferred via dike aspect ratios
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DOI：
10.1038/s41598-020-66226-z
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发表时间：
2020-06-10
影响因子：
4.6
通讯作者：
Kusumoto, Shigekazu
中科院分区：
文献类型：
--
作者：
Geshi, Nobuo;Browning, John;Kusumoto, Shigekazu
富含出溶挥发物（气泡）的浮力岩浆驱动岩浆房中的补给岩脉快速向上扩展。供给岩脉到达地表的后果可能导致火山爆发，部分取决于挥发物的保留。因此，及时检测的囊泡和超压的岩浆在馈线堤上升是至关重要的预测爆炸性的任何未来的喷发。在这项研究中，我们评估了喷发的爆炸性的基础上，现场调查的喷发产品和超压的岩浆在导管的基础上暴露的馈线堤防的尺寸。我们发现三宅岛火山最近几次裂隙喷发时，喷发的爆发性与通道中产生的岩浆超压之间存在正相关关系。由于低密度岩浆的浮力在岩脉顶部产生正超压，因此具有高度泡状岩浆的补给岩脉具有高的超压量。岩浆超压扩大了补给岩墙的开口宽度，导致更高的泡状岩浆流量，从而引起剧烈的爆炸活动。我们的研究结果表明，预测即将爆发的爆炸性的可能性，如果上升的馈线堤坝的宽度（或开口）进行实时监测，通过测量的地面变形和地震引起的堤坝。
Buoyant magmas abundant in exsolved volatiles (bubbles) drive the rapid upward-propagation of feeder dikes from magma chambers. The consequence of a feeder dike reaching the surface can result in an explosive volcanic eruption depending, partly, on the retention of volatiles. Therefore, timely detection of the vesicularity and overpressure of the magma during feeder dike ascent is critical for the prediction of the explosivity of any future eruption. In this study, we evaluated the explosivity of eruptions based on field investigations of the erupted products and the overpressure of magma in the conduit based on the dimensions of exposed feeder dikes. We found a positive correlation between the explosivity of eruptions and the magma overpressure generated in the conduit during recent fissure eruptions of Miyakejima volcano. Because the buoyancy of low-density magma produces positive overpressure at the dike's top, feeder dikes with highly-vesiculated magmas possess high amounts of overpressure. An enlargement of the opening width of a feeder dike by magmatic overpressure results in a higher flux of vesiculated magma, which causes vigorous explosive activity. Our results suggest the possibility of forecasting the explosivity of an impending eruption if the width (or opening) of an ascending feeder dike is monitored in real-time through measurements of ground deformation and seismicity induced by the dike.