Tephra From the 3 March 2015 Sustained Column Related to Explosive Lava Fountain Activity at Volcán Villarrica (Chile)
Tephra From the 3 March 2015 Sustained Column Related to Explosive Lava Fountain Activity at Volcán Villarrica (Chile)
复制标题
来自 2015 年 3 月 3 日与维拉里卡火山（智利）爆炸熔岩喷泉活动相关的持续柱的火山灰
DOI：
10.3389/feart.2018.00098
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发表时间：
2018
影响因子：
2.9
通讯作者：
Werner Keller
中科院分区：
文献类型：
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作者：
J. E. Romero;Franco Vera;M. Polacci;D. Morgavi;F. Arzilli;M. A. Alam;J. Bustillos;A. Guevara;Jeffrey B. Johnson;J. L. Palma;M. Burton;E. Cuenca;Werner Keller
至少自 1984-85 年以来，智利安第斯山脉南部的比亚里卡火山持续持续存在开放管道活动，与动态熔岩湖相关。 2014 年 8 月地震活动和排气量增加后，斯特龙博利活动从 2015 年 2 月开始增加，并于 2015 年 3 月 3 日达到顶峰，形成 1.5 公里高的熔岩喷泉。这次喷发产生了火山灰沉降物、飞溅凝集物、碎裂熔岩和混合雪崩沉积物。 2017 年和 2018 年开展的实地工作重点关注 2015 年 3 月 3 日阵发性喷发的火山灰沉积物。这里首次描述了由熔岩喷泉产生的火山灰沉积物以及比亚里卡向持续喷发柱的快速过渡。在火山口东南部的一个狭窄、细长、近椭圆形的区域中观察到了火山灰的分散。在侧风位置观察到的最小火山灰负载估计为 80-120 g/m2，而在距通风口 7-9 公里处的最大负载估计约为 11,500 g/m2。在顺风 6-8 公里处，火山灰坠落沉积物由单个黑色熔渣层组成，坠落范围从中间距离（9-19 公里）的火山灰覆盖到远端（20-43 公里）的一些单独颗粒不等。所有样品的结构均为玻璃状，具有斜长石 (3-30%)、单斜辉石 (2-5%)、橄榄石 (1-4%) 和稀有斜方辉石 (<1%) 斑晶的矿物组合。我们估计，约 16 分钟内喷发了 1.4 x 109 千克，相当于约 2.4 x 106 立方米的玄武安山岩火山灰（52.8 至 54.7 SiO2 wt.%），喷发速率约为 1.5 x 106 千克/秒。持续喷发柱高度估计约为10.8公里，震级和强度分别为2.11和9.13。我们认为，重新焕发活力的、富含挥发物的岩浆侵入是这次火山爆发的可能触发因素。比亚里卡喷发被归类为短暂的大型熔岩喷泉，类似于历史上埃特纳火山和基拉韦厄火山的强烈熔岩喷泉。正如 20 世纪维拉里卡毁灭性的火山喷发所证明的那样，该火山喷发也产生了类似的熔岩喷泉行为，这种喷发方式应被视为频繁的，并且是未来火山灾害的潜在来源。
Villarrica Volcano in the Southern Andes of Chile has sustained persistent open conduit activity, associated with a dynamic lava lake since at least 1984-85. Increased seismic activity and degassing in August 2014 was followed by increased Strombolian activity starting in February 2015 and culminated with a 1.5 km-high lava fountain on 3 March 2015. This eruption produced tephra fallout, spatter agglutination, clastogenic lavas and mixed avalanche deposits. Field work carried out in 2017 and 2018 focused upon the tephra fallout deposits from the 3 March 2015 paroxysmal eruption. Tephra fall deposits produced by lava fountain and a rapid transition to sustained eruption column at Villarrica are here described for first time. Tephra dispersion was observed mostly southeast of the crater in a narrow, elongated, nearly-elliptic area. Minimum observed tephra loading was estimated to be 80-120 g/m2 at crosswind locations, while maximum load estimation was about 11,500 g/m2, at 7-9 km distance from the vent. At 6-8 km downwind, the tephra fall deposit consisted of a single black scoria layer, fall varied from a lapilli blanket at medial distances (9-19 km) to a few individual particles at distal sites (20-43 km). All samples are vitrophyric in texture, with a mineral assemblage of plagioclase (3-30 %), clinopyroxene (2-5 %), olivine (1-4 %) and scarce orthopyroxene (<1 %) phenocrysts. We estimate that 1.4 x 109 kg, equivalent to ~2.4 x 106 m3 of basaltic andesite tephra (52.8 to 54.7 SiO2 wt. %), were erupted within a period of about 16 minutes at a mass eruption rate of ~1.5 x 106 kg/s. The sustained eruption column height was estimated at ~10.8 km, with magnitude and intensity of 2.11 and 9.13 respectively. We propose that a rejuvenated, volatile-rich magmatic intrusion is the probable triggering factor for the paroxysm. The Villarrica eruption is classified as a short-lived, large-scale lava fountain, similar to intense historical lava fountains at Mt. Etna and Kilauea. As evident by devastating 20th century Villarrica eruptions which also developed similar lava fountain behavior, this eruption style should be considered as frequent and a potential source of volcanic hazard in the future.