EAR-PF: Investigating the Explosive Effect of External Water on Volcanic Eruptions: Developing a Scalable Simulation of Explosion Energetics

Erin Fitch博士被授予NSF EAR博士后奖学金，以开发可扩展的、在火山喷发期间爆炸的岩浆-水相互作用的数值模拟。这项工作将在俄勒冈大学约瑟夫·杜菲克博士的指导下进行。在火山喷发期间，岩浆与外部水或冰相互作用，导致强烈的蒸汽爆炸。已知近30%的火山喷发涉及岩浆-水相互作用，而且可能在几乎没有预警的情况下发生，如2019年的白岛火山喷发和2014年的Ontake火山喷发，这就需要开发专门考虑岩浆-水相互作用的预测工具。岩浆-水相互作用的复杂性及其造成的危险条件使这一过程很难研究，特别是很难用传统的野外方法进行量化。因此，我们将开发和验证一种新的岩浆-水相互作用的数值模拟，该模拟考虑了微观热传递和破碎的过程，这些过程驱动了喷出物(固化岩浆)的宏观爆炸性膨胀、破碎和扩散。模拟将使我们能够估计岩浆-水爆炸能量，以便为火山危险评估提供信息。此外，PI将积极参与俄勒冈大学的教育活动，开发专门侧重于将现场和实验室观察与数值模拟联系起来的教育材料，这是学术教育的一个欠发达领域。这项工作的研究和教育目标直接影响到主办机构所在的以水火山作用和爆发而闻名的喀斯喀特火山弧的危险评估。为了改进火山作用危险评估，这项工作特别侧重于对岩浆-水相互作用过程的量化。以前，岩浆-水相互作用的能量学是基于矿床特征进行量化的，这可能涉及大量的不确定性，因为岩浆气体膨胀和外部水都有助于火山灰的破碎和扩散。然而，爆炸性的岩浆-水相互作用是由与熔岩-水爆炸和爆炸性融水实验相同的机制驱动的，因此我们可以利用后者来理解前者。这种机制是熔融-燃料-冷却剂相互作用(MFCI)，其中“熔融燃料”是岩浆或熔岩，而“冷却剂”是外部水。为了观察微尺度的MFCI过程并确定它们在岩浆-水相互作用过程中的进展情况，我们利用实验室实验和熔岩-水爆炸的大量新数据和现有数据，使用灵活的行业标准软件开发了第一个可扩展的熔融-水混合数值模拟。我们的预期结果解决了对自然系统仍然知之甚少的过程，即(1)影响界面混合和不稳定性的因素，特别是汽膜崩溃，(2)转化率和水/熔体质量比之间的关系，以及(3)通过快速热传递驱动爆炸的活性粒子的产生。正在进行的这一模拟将使其能够被用作了解和预测与熔岩水爆炸和火山喷发有关的危险的工具。该奖学金的教育方面包括开发教育材料，其中包括结合数值模拟使用的实验室实验。该奖学金由地球科学部的岩石学和地球化学项目共同资助。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Dr. Erin Fitch has been awarded an NSF EAR Postdoctoral Fellowship to develop a scalable, numerical simulation of explosive magma–water interaction during hydrovolcanic eruptions. This work will be pursued under the mentorship of Dr. Josef Dufek at the University of Oregon. During hydrovolcanic eruptions, magma interacts with external water or ice, resulting in vigorous steam explosions. Almost 30% of volcanic eruptions are known to involve magma–water interactions and can occur with very little warning, like at White Island in 2019 and Ontake in 2014, necessitating the development of forecasting tools that account specifically for magma–water interactions. The complexity of magma–water interactions and the hazardous conditions they create make this a difficult process to study, and especially difficult to quantify by traditional field methods. We will therefore develop and validate a new numerical simulation of magma–water interactions, which takes into account the progression of micro-scale heat transfer and fragmentation that drives macro-scale explosive expansion, fragmentation, and dispersal of ejecta (solidified magma). The simulation will allow us to estimate magma–water explosion energy to inform volcanic hazard assessments. Additionally, the PI will be actively involved in educational activities at the University of Oregon by developing educational material specifically focused on tying field and laboratory observations to numerical simulations, which is an underdeveloped area of academic education. The research and education goals of this work directly impact the hazard assessment of the Cascade Volcanic Arc, known for hydrovolcanism and explosive eruptions, where the host institution is located.In order to improve hydrovolcanism hazard assessment, this work focuses specifically on the quantification of processes occurring during magma–water interactions. Previously, the energetics of magma–water interactions was quantified based on deposit characteristics, which can involve a significant amount of uncertainty, because magmatic gas expansion and external water both contribute to the fragmentation and dispersal of tephra. However, explosive magma–water interactions are driven by the same mechanism as lava–water explosions and explosive melt–water experiments, so we can use the latter to understand the former. This mechanism is Molten-Fuel-Coolant Interaction (MFCI) where the “molten fuel” is magma or lava and the “coolant” is external water. In order to take observations of micro-scale MFCI processes and determine how they progress during magma–water interactions, we use the breadth of new and existing data on laboratory experiments and lava–water explosions to develop the first scalable numerical melt–water mixing simulation, using flexible industry-standard software. Our expected results address processes that are still poorly understood for natural systems, namely (1) the factors affecting interfacial mixing and instabilities, especially vapor film collapse, (2) the relationship between the conversion ratio and water/melt mass ratio, and (3) the production of active particles, which drive the explosion through rapid heat transfer. Ongoing development of this simulation will enable it to be used as a tool to understand and forecast hazards associated with lava–water explosions and hydrovolcanic eruptions. Educational aspects of the fellowship include developing educational materials that include laboratory experiments used in conjunction with numerical simulations. This fellowship received co-funding from the Petrology and Geochemistry program in the Earth Science division.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.