Transient magma permeability and gas flow: a combined experimental and theoretical model

由于浮力，岩浆在地壳中上升-这一特性主要由气泡的存在控制。事实上，如果没有气泡的存在，岩浆不会轻易喷发;相反，可以说是气泡的存在将岩浆拖到地球表面。因此，了解气体和岩浆之间的关系是了解火山爆发的核心。当岩浆穿过地壳上升时，压力下降，这导致气泡的形成（就像打开一瓶香槟）。当气泡膨胀时，它们相互作用，形成一个可渗透的多孔网络，气体可以通过该网络逸出。如果有足够的气体逸出，气泡状的岩浆会停止或流出火山，形成熔岩流，但如果气体压力仍然被困在气泡中，岩浆可能会猛烈破碎，导致爆炸性喷发。因此，火山岩渗透性的发展控制着火山气体的释放、火山喷发的类型和火山灾害的严重程度。这项工作表明，渗透率一般增加的岩石中的孔隙的分数。然而，火山岩是固体（因为它们在喷发后冷却），他们的研究并没有为我们提供有关变形岩浆流动和喷发时的渗透性的信息。在这里，我们将使用利物浦大学最近开发的最先进的设备来复制浅火山管道中的岩浆条件。我们将进行一系列新颖的实验来测量多孔岩浆在熔融状态和变形时的渗透性。我们将测试一系列与气体冲刷（可渗透）岩浆相关的条件，并了解多孔泡沫如何随着不同压力条件的变化而变形。利用这些数据，我们将开发，测试，验证和完善一个理论模型，以解决火山条件下多孔岩浆中的流体流动。限制岩浆渗透性和压缩性的实验室结果将被整合到一个数据库中，用于未来的建模工作，开发的模型将有助于我们了解火山动荡期间监测到的气体排放。这个经过实验验证的模型将成为更好地预测火山爆发的垫脚石。

Magma ascends in the Earth's crust due to buoyancy - a property mainly controlled by the presence of gas bubbles. In fact, without the presence of gas bubbles, magma would not readily erupt; rather, it may be said that it is the presence of gas bubbles that drags magma to the Earth's surface. Understanding the relationship between gas and magma is thus central to understanding volcanic eruptions.As magma ascends through the crust, pressure decreases, which leads to the formation of gas bubbles (like uncorking a bottle of Champagne). As gas bubbles expand, they interact, creating a permeable, porous network, through which gas can escape. If sufficient gas is able to escape, the bubbly magma will either halt or will effuse out of the volcano, forming lava flows, but if gas pressure remains trapped in bubbles, the magma may fragment violently, causing an explosive eruption. Thus the development of permeability in flowing magma controls the release of gas from volcanoes, the style of volcanic eruptions and the severity of volcanic hazards.The permeability of volcanic rocks has been extensively studied in the past 3 decades. This work suggests that permeability generally increases with the fraction of pores in a rock. Yet, volcanic rocks are solids (as they cooled following eruption) and their study does not provide us with information about the permeability of deforming magma as it flows and erupts. Here, we will use state-of-the-art equipment recently developed at the University of Liverpool to replicate magmatic conditions in shallow volcanic conduits. We will conduct a series of novel experiments to measure the permeability of porous magma in its molten state and as it deforms. We will test a range of conditions relevant to gas flushing through (permeable) magma and see how the porous foam deforms as a function of different pressure conditions. Using this data we will develop, test, verify and refine a theoretical model to resolve fluid flow in porous magma subjected to volcanic conditions. The laboratory results constraining the permeability and compressibility of magma will be integrated into a database for future modelling efforts, and the model developed will be made available to help our understanding of gas emissions monitored during volcanic unrest. This experimentally validated model will be stepping-stone towards better forecasts of volcanic eruptions.