Groundwater drainage from fissures as a source for lahars
Groundwater drainage from fissures as a source for lahars
复制标题
从裂缝中排出的地下水是火山泥流的来源
DOI：
10.1007/s00445-018-1214-4
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发表时间：
2018
影响因子：
3.5
通讯作者：
A. Agudelo
中科院分区：
文献类型：
--
作者：
P. J. Johnson;G. Valentine;P. H. Stauffer;C. Lowry;I. Sonder;B. Pulgarín;C. C. Santacoloma;A. Agudelo
在经历动荡的火山中产生火山灰的一种机制是内部含水层的破坏。这些破坏可能会引发大量地下水的释放。2007年2月至4月期间，哥伦比亚内华多德尔维拉火山发生了这种含水层破坏的例子，当时火山顶端形成了大裂缝，并从这些裂缝中排放出岩浆。以前的工作解释说，冰川融化的积雪或降水不能解释火山灰的数量，而消除冰川融化的冰川表明，主要的水源是地下水。已经建立了栖息的承压含水层的概念模型，这些含水层在岩浆侵入作用下被加热和加压，然后在裂缝形成期间突然释放压力和水。我们考虑另一种末端构件，其中火山大裂隙的水释放是由简单的重力排水驱动的。我们应用数值模拟来量化从具有低海拔自由出口的裂隙周围的多孔介质中排放的水。如果一条高垂直范围的长裂缝(大约数百米)与高度连通的饱和多孔介质相交，可能会在几十分钟内释放大量的水(大约103立方米/米的裂缝长度)。如果裂缝周围的介质含有大量的水，并且具有很高的水平渗透率，则模型的排水速率可能足以解释内华多-德尔惠拉事件。这种简单但鲜为人知的机制本身可能会带来危险，也可能会与其他从火山释放水的过程相结合。
One mechanism for generating lahars at volcanoes experiencing unrest is the disruption of internal aquifers. These disruptions can trigger releases of large quantities of groundwater. An example of such aquifer disruption occurred at Nevado del Huila Volcano, Colombia, during February and April 2007 when large fractures formed across the summit area of the volcano and lahars were emitted from them. Previous work interpreted that lahar volumes could not be accounted for by melted glacial snow or precipitation, and by elimination suggested that the primary water source was groundwater. Conceptual models have been developed for perched, confined aquifers that have been heated and pressurized by magma intrusions, followed by sudden pressure release and water emission during fracture formation. We consider an alternative end member wherein water release from large fissures at volcanoes is driven by simple gravity drainage. We apply numerical modeling to quantify water discharge from the porous medium surrounding a fissure with a low-elevation free exit. If a long fracture with high vertical extent (on the order of hundreds of meters) intersects a highly connected saturated porous medium, large volumes (on order 103 m3/m of crack length) of water may be released within tens of minutes. The drainage rates from the model may be adequate to account for the Nevado del Huila events if the medium surrounding the crack contains a large volume of water and has high horizontal permeability. This simple but poorly understood mechanism can present a hazard on its own or compound other processes releasing water from volcanoes.