A new model for the growth of basaltic shields based on deformation of Fernandina volcano, Galapagos Islands
A new model for the growth of basaltic shields based on deformation of Fernandina volcano, Galapagos Islands
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DOI：
10.1016/j.epsl.2013.07.016
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发表时间：
2013-09-01
影响因子：
5.3
通讯作者：
Poland, Michael P.
中科院分区：
文献类型：
--
作者：
Bagnardi, Marco;Amelung, Falk;Poland, Michael P.
对费尔南迪纳火山--加拉帕戈斯群岛最频繁喷发的火山--最近一次喷发造成的地表变形进行的空间大地测量表明，所有这些都是从浅层岩浆储集层的次水平岩床侵入开始的。这包括从相对于顶端火山口径向和圆周方向的裂缝喷发。合成孔径雷达(SAR)在2009年放射状裂缝喷发开始前1-2小时拍摄到的图像捕捉到了其中一个正在向地表传播的岩床。加拉帕戈斯所有方向的喷发裂缝以前都被认为是由垂直岩脉提供的，这一假设指导了喷发裂缝几何形状的起源和火山的整体发展的模型。我们的发现使我们能够重新解释加拉帕戈斯火山和类似玄武岩地盾的内部结构和演化。此外，我们注意到，为一种类型的喷发提供补给的次水平岩床所产生的应力变化可能控制随后喷发裂缝的几何形状。具体地说，环向裂缝倾向于在由基床侵入而抬升的区域内打开，这些侵入物引发了先前的放射状裂缝喷发。这一机制为所有西加拉帕戈斯火山的喷发裂缝模式以及费尔南迪纳的径向和周向裂缝喷发之间的交替提供了可能的解释。同样的模型表明，费尔南迪纳火山的下一次喷发将来自2009年底底侵入物抬升的地区的一个环状裂缝，就在火山口边缘的西南部。(C)2013爱思唯尔B.V.保留所有权利。
Space-geodetic measurements of surface deformation produced by the most recent eruptions at Fernandina - the most frequently erupting volcano in the Galapagos Archipelago - reveal that all have initiated with the intrusion of subhorizontal sills from a shallow magma reservoir. This includes eruptions from fissures that are oriented both radially and circumferentially with respect to the summit caldera. A Synthetic Aperture Radar (SAR) image acquired 1-2 h before the start of a radial fissure eruption in 2009 captures one of these sills in the midst of its propagation toward the surface. Galapagos eruptive fissures of all orientations have previously been presumed to be fed by vertical dikes, and this assumption has guided models of the origin of the eruptive fissure geometry and overall development of the volcanoes. Our findings allow us to reinterpret the internal structure and evolution of Galapagos volcanoes and of similar basaltic shields. Furthermore, we note that stress changes generated by the emplacement of subhorizontal sills feeding one type of eruption may control the geometry of subsequent eruptive fissures. Specifically, circumferential fissures tend to open within areas uplifted by sill intrusions that initiated previous radial fissure eruptions. This mechanism provides a possible explanation for the pattern of eruptive fissures that characterizes all the western Galapagos volcanoes, as well as the alternation between radial and circumferential fissure eruptions at Fernandina. The same model suggests that the next eruption of Fernandina will be from a circumferential fissure in the area uplifted by the 2009 sill intrusion, just southwest of the caldera rim. (C) 2013 Elsevier B.V. All rights reserved.