A critical magma chamber size for volcanic eruptions
A critical magma chamber size for volcanic eruptions
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DOI：
10.1130/g47045.1
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发表时间：
2020-05-01
期刊：
影响因子：
5.8
通讯作者：
Huber, Christian
中科院分区：
文献类型：
--
作者：
Townsend, Meredith;Huber, Christian
我们提出了一个耦合岩浆室-岩脉系统的模型，以研究引发火山喷发所需的条件，并确定是什么控制了喷发的规模。该模型结合了岩脉传播机制和内部洞室动力学，包括结晶、挥发分出溶，以及岩浆和周围地壳对洞室内压力变化的弹性响应。我们发现了岩脉生长和喷发的三种模式：(1)在临界岩浆室尺寸以下，由于岩浆室压力在岩浆岩到达地表之前降至止岩，所以喷发受到抑制；(2)在中等岩浆室尺寸下，喷发量小于岩墙体积(“岩墙受限”喷发区)；(3)在某一岩浆室大小以上，岩脉很容易到达地表，喷发量遵循经典的标度规律，这取决于岩浆室的属性(“洞限区”喷发区)。根据岩浆中的水分含量、洞室深度和初始超压，喷发的临界洞室体积从类似的0.01公里(3)到10公里(3)。这意味着，在火山第一次喷发之前，可能会有一段漫长的岩浆室深度增长历史，岩浆室上方的地壳可能已经捕获了几次侵入或“失败的喷发”。模型结果可以与喷发体积、压力、晶体和挥发分含量的现场观测相结合，以提供对可喷发室大小等参数的更严格限制。
We present a model for a coupled magma chamber-dike system to investigate the conditions required to initiate volcanic eruptions and to determine what controls the size of eruptions. The model combines the mechanics of dike propagation with internal chamber dynamics including crystallization, volatile exsolution, and the elastic response of the magma and surrounding crust to pressure changes within the chamber. We find three regimes for dike growth and eruptions: (1) below a critical magma chamber size, eruptions are suppressed because chamber pressure drops to lithostatic before a dike reaches the surface; (2) at an intermediate chamber size, the erupted volume is less than the dike volume ("dike-limited" eruption regime); and (3) above a certain chamber size, dikes can easily reach the surface and the erupted volume follows a classic scaling law, which depends on the attributes of the magma chamber ("chamber-limited" eruption regime). The critical chamber volume for an eruption ranges from similar to 0.01 km(3) to 10 km(3) depending on the water content in the magma, depth of the chamber, and initial overpressure. This implies that the first eruptions at a volcano likely are preceded by a protracted history of magma chamber growth at depth, and that the crust above the magma chamber may have trapped several intrusions or "failed eruptions." Model results can be combined with field observations of erupted volume, pressure, and crystal and volatile content to provide tighter constraints on parameters such as the eruptible chamber size.