Volcano load control on dyke propagation and vent distribution: Insights from analogue modeling
Volcano load control on dyke propagation and vent distribution: Insights from analogue modeling
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DOI：
10.1029/2008jb005653
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发表时间：
2009-03-03
影响因子：
3.9
通讯作者：
Jacobs, P.
中科院分区：
文献类型：
--
作者：
Kervyn, M.;Ernst, G. G. J.;Jacobs, P.
火山周围的喷发口的空间分布可能是复杂的，并随着火山的发展而演变。在对比火山口分布的观测，从火山渣锥到大盾，表明周边喷发口集中在靠近火山基地。我们使用模拟实验来探讨火山负荷对岩浆上升和喷口位置的控制。结果表明，如果没有建立中心通道或通道被堵塞，局部加载应力场有利于岩浆远离火山顶喷发。通过对比流变学特性，设计了两组模拟火山岩浆上升的相似性和差异性实验：（1）将金浆（岩浆模拟物）注入锥体下的砂-膏混合层（地壳模拟物）;（2）将水或空气（岩浆模拟物）注入锥体下的明胶中。上升岩墙靠近锥应力场时被荷载压应力所阻止。随着持续的侵入，岩脉超压逐渐增加;岩脉横向延伸，直到其尖端能够再次垂直上升，并在火山的侧翼或底部喷发。挤出点相对于建筑物顶峰的侧向偏移取决于基底厚度、火山坡度和岩脉超压。金糖浆侵入体的3D几何形状随实验参数而变化，从圆柱形导管到岩墙和岩床复合体。实验结果进行了比较，说明现场的情况下，与以前发表的数值模型。这种比较使应用程序和模拟模型的局限性被突出，并使我们能够提出一个概念模型的火山喷发分布的演变与火山的增长。
The spatial distribution of eruptive vents around volcanoes can be complex and evolve as a volcano grows. Observations of vent distribution at contrasting volcanoes, from scoria cones to large shields, show that peripheral eruptive vents concentrate close to the volcano base. We use analogue experiments to explore the control of volcano load on magma ascent and on vent location. Results show that the local loading stress field favors eruption of rising magma away from the volcano summit if a central conduit is not established or is blocked. Two sets of scaled experiments are developed with contrasting rheological properties to analyze similarities and differences in simulated magma rise below a volcano: (1) Golden syrup (magma analogue) is injected into a sand-plaster mixed layer (crust analogue) under a cone; ( 2) water or air (magma analogues) is injected into gelatin under a sand cone. Rising dykes approaching the cone stress field are stopped by the load compressive stress. With continued intrusion, dyke overpressure builds up; dykes extend laterally until their tips are able to rise vertically again and to erupt in the flank or at the base of the volcano. Lateral offset of the extrusion point relative to the edifice summit depends on substratum thickness, volcano slope, and dyke overpressure. The 3D geometry of Golden syrup intrusions varies with experimental parameters from cylindrical conduits to dyke and sill complexes. Experimental results are compared with illustrative field cases and with previously published numerical models. This comparison enables applications and limitations of the analogue models to be highlighted and allows us to propose a conceptual model for the evolution of vent distribution with volcano growth.