Rapid ascent of rhyolitic magma at Chaiten volcano, Chile
Rapid ascent of rhyolitic magma at Chaiten volcano, Chile
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DOI：
10.1038/nature08458
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发表时间：
2009-10-08
期刊：
影响因子：
64.8
通讯作者：
Dingwell, Donald B.
中科院分区：
文献类型：
--
作者：
Castro, Jonathan M.;Dingwell, Donald B.
流纹岩岩浆为地球上一些最大的火山爆发提供了燃料。然而，由于之前缺乏直接观测到的喷发，我们对这些事件的理解是不完整的。2008年5月1日，智利北部巴塔哥尼亚的Chaiten火山意外爆发流纹岩岩浆（参考资料2）。柴滕镇的居民在火山灰落在他们的城镇前大约24小时感到地震，火山喷发升级为普林尼柱状火山。虽然对玄武岩大爆发的如此短暂的地震预警已有文献记载(3)，但对硅质岩浆来说，这是前所未有的。由于火山动荡前兆与岩浆从储区向地表迁移有关，因此柴滕火山爆发前的短暂预警可能反映了岩浆在次火山体系中的快速上升。在这里，我们提出了岩石学和实验数据，表明在Chaiten的含水流纹岩岩浆上升非常迅速，速度为每秒一米。如此快速的上升意味着从储存深度大于5公里到近地表的传输时间大约为4小时。这一结果对减轻危险具有启示意义，因为流纹岩上升的速度意味着未来的喷发可能几乎没有预警。
Rhyolite magma has fuelled some of the Earth's largest explosive volcanic eruptions(1). Our understanding of these events is incomplete, however, owing to the previous lack of directly observed eruptions. Chaiten volcano, in Chile's northern Patagonia, erupted rhyolite magma unexpectedly and explosively on 1 May 2008 (ref. 2). Chaiten residents felt earthquakes about 24 hours before ash fell in their town and the eruption escalated into a Plinian column. Although such brief seismic forewarning of a major explosive basaltic eruption has been documented(3), it is unprecedented for silicic magmas. As precursory volcanic unrest relates to magma migration from the storage region to the surface, the very short pre-eruptive warning at Chaiten probably reflects very rapid magma ascent through the sub-volcanic system. Here we present petrological and experimental data that indicate that the hydrous rhyolite magma at Chaiten ascended very rapidly, with velocities of the order of one metre per second. Such rapid ascent implies a transit time from storage depths greater than five kilometres to the near surface in about four hours. This result has implications for hazard mitigation because the rapidity of ascending rhyolite means that future eruptions may provide little warning.