The 2011-2012 summit activity of Mount Etna: Birth, growth and products of the new SE crater
The 2011-2012 summit activity of Mount Etna: Birth, growth and products of the new SE crater
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DOI：
10.1016/j.jvolgeores.2013.11.012
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发表时间：
2014-01-15
影响因子：
2.9
通讯作者：
Proietti, Cristina
中科院分区：
文献类型：
--
作者：
Behncke, Boris;Branca, Stefano;Proietti, Cristina
2011年1月至2012年4月期间，埃特纳火山的东南火山口（SEC）发生了25次熔岩喷发，在SEC的东侧翼形成了一个新的火山碎屑锥。在这些喷发期间，熔岩溢出的长度达到43公里，面积为3.19公里，体积为28 × 106米。这个新的火山口被非正式地称为新东南火山口（NSEC），它是在2007-2009年形成的一个原有的下沉洼地（坑坑）上形成的。NSEC锥体的演变从一开始就被记录下来，包括从远处和锥体本身进行的重复GPS调查，以及获得的比较照片。这些调查表明，在2012年4月熔岩喷泉停止后，NSEC的最高点位于前锥体表面上方190 m处，而锥体体积约为19 x 106 m(3)，占2011-2012年喷发的火山产物（包括火山碎屑沉降物）总（体积）体积的38%，即50 x 106 m（3)（约33 x 106 m(3)）致密岩石当量）。新锥体的生长只发生在熔岩喷发的阵发性阶段，几乎总是相当短暂（平均2小时）。总的来说，所有25次喷发的爆发阶段代表了51小时的熔岩喷发活动，这是建造火山锥所需的时间。2011年8月20日（E11）以及2012年4月12日和24日（E24和E25）熔岩喷发期间的平均喷发速率超过500米(3)/秒（E11期间的最大喷发速率为980米(3)/秒），因此它们是埃特纳火山有记录以来最高的喷发速率之一。喷发产物的组成随时间的变化而变化，反映了岩浆进入浅层补给系统的速率不同，但对喷发现象学无显著影响。这意味着导致间歇性熔岩喷涌的动力学在很大程度上（尽管不是完全）由NSEC岩浆储层最上层泡沫层的反复形成和崩塌控制。(C) 2013 Elsevier B.V.版权所有
Between January 2011 and April 2012, the Southeast Crater (SEC) on Mount Etna was the site of 25 episodes of lava fountaining, which led to the construction of a new pyroclastic cone on the eastern flank of the SEC. During these episodes lava overflows reached 43 km in length with an area of 3.19 km(2) and a volume of 28 x 106 m(3). The new cone, informally called New Southeast Crater (NSEC), grew over a pre-existing subsidence depression (pit crater), which had been formed in 2007-2009. The evolution of the NSEC cone was documented from its start by repeated GPS surveys carried out both from a distance and on the cone itself, and by the acquisition of comparison photographs. These surveys reveal that after the cessation of the lava fountains in April 2012, the highest point of the NSEC stood 190 m above the pre-cone surface, while the cone volume was about 19 x 106 m(3), representing 38% of the total (bulk) volume of the volcanic products including pyroclastic fallout erupted in 2011-2012, which is 50 x 106 m(3) (about 33 x 106 m(3) dense-rock equivalent). Growth of the new cone took place exclusively during the paroxysmal phases of the lava fountaining episodes, which were nearly always rather brief (on the average 2 h). Overall, the paroxysmal phases of all 25 episodes represent 51 h of lava fountaining activity the time needed to build the cone. This is the fastest documented growth of a newborn volcanic cone both in terms of volume and height Mean effusion rates during the lava fountaining episodes on 20 August 2011 (E11), as well as 12 and 24 April 2012 (E24 and E25) exceeded 500 m(3)/s (with maximum rates of 980 m(3)/s during E11) and thus they are among the highest effusion rates ever recorded at Etna. The composition of the erupted products varies in time, reflecting different rates of magma supply into the shallow feeding system, but without notable effects on the eruptive phenomenology. This implies that the dynamics leading to the episodic lava fountaining was largely, though not entirely, controlled by the repeated formation and collapse of a foam layer in the uppermost portion of the magmatic reservoir of the NSEC. (C) 2013 Elsevier B.V. All rights reserved.