Anatomy of a lava dome collapse: the 20 March 2000 event at Soufriere Hills Volcano, Montserrat
Anatomy of a lava dome collapse: the 20 March 2000 event at Soufriere Hills Volcano, Montserrat
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DOI：
10.1016/s0377-0273(03)00364-0
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发表时间：
2004-03-30
影响因子：
2.9
通讯作者：
Norton, GE
中科院分区：
文献类型：
--
作者：
Carn, SA;Watts, RB;Norton, GE
1995-2003 年蒙特塞拉特苏弗里埃尔山火山 (SHV) 目前正在进行的第二次喷发阶段于 1999 年 11 月中旬开始，此前有 19 个月没有新鲜熔岩到达地表。到 2000 年 3 月中旬，在 1995-1998 年圆顶建筑群的残余物环绕的塌陷疤痕内建造了一个新的安山岩熔岩圆顶，其估计体积约为 29+/-3 百万米 (3) (Mm(3))。 2000 年 3 月 20 日，在岛上的一场强降雨期间，随后发生了一次严重的塌陷事件，在大约 5 小时的活动期间，大约 95% 的新熔岩穹顶（大约 28+/-3 Mm(3)）被移除，产生了大约 40 次火山碎屑流和至少一次岩浆爆炸。伴随而来的火山灰云达到了约9公里的高度，并在东南部的瓜德罗普岛沉积了火山灰，在SHV侧翼的山谷中出现了许多火山泥流和泥石流。大量观测数据，包括同期现场观测和来自蒙特塞拉特宽带地震台网的连续数据，可以详细重建这一穹顶倒塌事件。与 SHV 的大多数大型穹顶塌陷相比，2000 年 3 月 20 日的事件的特点是，在熔岩穹顶下方的浅层深处缺乏短期前兆的高地震活动。事件期间记录的宽带地震振幅数据用于推断随着塌陷的进展，塌陷穹顶的累积体积。这些数据表明，在事件高潮时观察到的高速火山碎屑流以大约 2 x 10(4) m(3) s(-1) 的峰值排放速率（根据地震记录估计）清除了熔岩穹顶的最大部分（大约 68%）。 2000年3月20日塌陷后，熔岩穹顶立即重新开始生长，并持续不断地生长，直到2001年7月29日发生另一次更大的穹顶塌陷。2001年7月29日的事件也与蒙特塞拉特岛的强降雨同时发生[Matthews等人，2001年]。 (2002)地球物理学。资源。莱特。 29； DOI：10.1029/2002GL014863]并且缺乏前兆的地震活动增强。我们将 2000 年 3 月 20 日崩塌的开始归因于事件发生前和事件期间熔岩穹顶上的长时间强降雨。确切的因果机制仍然存在争议，尽管机械侵蚀和/或熔岩穹顶临界面的不稳定、加压蒸汽或水对穹顶内潜在破坏表面的作用、热熔岩的快速冷却和小型潜水爆炸的某种组合似乎是有可能的。蒙特塞拉特岛存在其他由降雨引起的活动的轶事证据，并且在其他地方的圆顶形成火山中也注意到降雨引发的爆炸或火山碎屑流活动，包括印度尼西亚默拉皮 [Voight 等人，2017]。 （2000）J.火山。地热。资源。 100, 69-138]，云仙，日本 [Yamasato 等人。 (1997) 气象学论文。地球物理学。 48]，危地马拉圣地亚哥[史密森学会全球火山网络公报。 15 (1990)] 和美国圣海伦斯山 [Mastin (1994) Geol。苏克。是。公牛。 106、175-185]。因此，气象预报和降雨监测设备的纳入将有利于圆顶火山的减灾计划，特别是在热带地区。 (C) 2003 Elsevier B.V. 保留所有权利。
A second extrusive phase of the currently ongoing 1995-2003 eruption of Soufriere Hills Volcano (SHV), Montserrat, commenced in mid-November 1999 following similar to19 months during which no fresh lava had reached the surface. By mid-March 2000, a new andesite lava dome constructed within a collapse scar girdled by remnants of the 1995-1998 dome complex had attained an estimated volume of similar to29+/-3 million m(3) (Mm(3)). On 20 March 2000, during a period of heavy rainfall on the island, a significant collapse event ensued that removed similar to95% of the new lava dome (similar to28+/-3 Mm(3)) during similar to5 hours of activity that generated similar to40 pyroclastic flows and at least one magmatic explosion. The associated ash cloud reached an altitude of similar to9 km and deposited ash on the island of Guadeloupe to the southeast, and a number of lahars and debris flows occurred in valleys on the flanks of SHV. A large quantity of observational data, including contemporaneous field observations and continuous data from the broadband seismic network on Montserrat, allow a detailed reconstruction of this dome collapse event. In contrast to most of the large dome collapses at SHV, the 20 March 2000 event is distinguished by a lack of short-term precursory elevated seismicity at shallow depths beneath the lava dome. Broadband seismic amplitude data recorded during the event are used to infer the cumulative volume of collapsed dome as the collapse progressed. These data indicate that the high-velocity pyroclastic flows observed at the climax of the event removed by far the largest portion (similar to68%) of the lava dome at peak discharge rates (estimated from the seismic record) of similar to2 x 10(4) m(3) s(-1). Following the 20 March 2000 collapse, lava dome growth recommenced immediately and continued without significant interruption until another, larger dome collapse occurred on 29 July 2001. The 29 July 2001 event also coincided with heavy rainfall on Montserrat [Matthews et al. (2002) Geophys. Res. Lett. 29; DOI: 10.1029/2002GL014863] and lacked precursory elevated seismic activity. We attribute the initiation of the 20 March 2000 collapse to a prolonged spell of heavy rainfall on the lava dome prior to and during the event. The precise causal mechanism remains controversial, though some combination of mechanical erosion and/or destabilization of a critically poised face of the lava dome, the action of pressurized steam or water on potential failure surfaces within the dome, rapid cooling of hot lava and small phreatic explosions seems likely. Anecdotal evidence exists for other rainfall-induced activity on Montserrat, and the triggering of explosive or pyroclastic flow activity by rainfall has been noted at dome-forming volcanoes elsewhere, including Merapi, Indonesia [Voight et al. (2000) J. Volcanol. Geotherm. Res. 100, 69-138], Unzen, Japan [Yamasato et al. (1997) Papers Meteorol. Geophys. 48], Santiaguito, Guatemala [Smithsonian Institution Global Volcanism Network Bull. 15 (1990)] and Mount St. Helens, USA [Mastin (1994) Geol. Soc. Am. Bull. 106, 175-185]. Hazard mitigation plans at dome-forming volcanoes would therefore benefit from the inclusion of meteorological forecasting and rain monitoring equipment, particularly in the tropics. (C) 2003 Elsevier B.V. All rights reserved.