Collaborative Research: A Self-consistent Model for Bubble Nucleation During Plinian Volcanic Eruptions

合作研究：普林尼火山喷发期间气泡成核的自洽模型

• 批准号: 1348072
• 负责人: Helge Gonnermann
• 金额: $ 24.59万
• 依托单位: William Marsh Rice University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-03-01 至 2018-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1348072&HistoricalAwards=false
• 关键词: Collaborative; Research; Self; consistent; Model

One of the large-impact natural hazards to affect humans on a decadal time scale are highly explosive Plinian volcanic eruptions, whose dynamics are thought to be intimately linked to the manner by which magmatic gases, such as water and carbon dioxide, escape from the erupting magma. Magma degassing begins with the nucleation of bubbles, which are preserved as vesicles in the erupted volcanic rock fragments. It is thought that the number and size of bubbles in a given volume of volcanic rock provide records of the forces that drive bubble nucleation and, by inference, the dynamics of the eruption. Specifically, the speed at which magma rises to the surface, thereby undergoing decompression, and the rate at which bubbles nucleate are thought to be correlated and affect the explosive intensity of an eruption. About one million bubbles may nucleate within a cubic millimeter of magma over fractions of a second to a few seconds. This transformation from dissolved gases to gaseous bubbles under high pressure is a key mechanism for explosive eruptions. Current models for the rate of bubble nucleation during explosive eruptions are based on Classical Nucleation Theory. A preliminary analysis of laboratory experiments of bubble nucleation in magmas, where conditions (pressure, rate of decompression, composition, content of dissolved gases, temperature) are well known and controlled, has shown that this classical theory fails to predict the rate at which bubbles nucleate across a wide range of conditions. A fundamental issue in this regard is the requirement for decompression rates that may be higher than physically attainable during an eruption, thus over-predicting rates of magma ascent.The objective of this project is to obtain a new formulation for the rate bubble nucleation, which will be applicable across a wide range of conditions of relevance to explosive volcanic eruptions. This will be accomplished through an integrated study that is comprised of laboratory experiments of bubble nucleation in silicate melts and detailed numerical modeling of these experiments. The result of this study, that is a new formulation for bubble nucleation in silicate melts, will be incorporated into numerical models of explosive volcanic eruptions, thereby enhancing their predictive capabilities. These models, in turn, will be used to resolve the question of what the precise relationship between magma decompression rate and the number of bubbles that nucleate within a given volume of magma is, thereby allowing a more robust integration of observationally based studies with quantitative predictions through numerical modeling and hazard assessment. Moreover, nucleation theory is of importance in a wide range of disciplines, such as for example chemical engineering and material science. Because this project will integrate recent advances in other fields where Classical Nucleation Theory has been found inadequate, it will advance the state-of-the-art and also have the potential to impact other disciplines.

在十年时间尺度上影响人类的大型自然危害之一是高度爆炸性的plinian火山喷发，其动态被认为与岩浆和二氧化碳等岩浆从爆发的岩浆中逃脱的岩浆气体（例如水和二氧化碳）的方式密切相关。岩浆脱气始于气泡的成核，这些气泡被保存为囊泡在爆发的火山岩碎片中。人们认为，在给定的一系列火山岩中气泡的数量和大小提供了驱动气泡成核的力的记录，并通过推断喷发的动力学。具体而言，岩浆升至表面的速度，从而经历了减压，而气泡成核的速度被认为是相关的并影响了喷发的爆炸性强度。在一秒钟到几秒钟的分数中，大约一百万个气泡可能会在立方毫米的岩浆中成核。从高压下，这种从溶解气体到气体气泡的转化是爆炸性喷发的关键机制。爆炸过程中气泡成核速率的当前模型基于经典成核理论。对岩浆中气泡成核实验室实验的初步分析，其中条件（压力，减压速率，成分，溶解气体的含量，温度）是众所周知的和控制的，表明该经典理论无法预测在各个条件下气泡成核的速率。在这方面的一个基本问题是，需要在喷发过程中高于物理上可达到的减压率的要求，因此过度预测的岩浆上升速率是该项目的目的是为速率泡泡成核的新配方提供新的配方，这将适用于与爆炸性火山爆发相关的广泛条件。这将通过一项综合研究来实现，该研究由硅酸盐融化中气泡成核的实验室实验以及这些实验的详细数值建模。这项研究的结果是硅酸盐融化中气泡成核的一种新配方，将纳入爆炸性火山喷发的数值模型，从而增强其预测能力。反过来，这些模型将用于解决一个问题，即岩浆减压率与给定岩浆内成核的气泡数量之间的确切关系是什么，从而允许通过数值建模和危害评估进行定量预测的基于观察性的研究和定量预测。此外，成核理论在广泛的学科中至关重要，例如化学工程和材料科学。因为该项目将在发现经典成核理论不足的其他领域中整合最新进展，因此它将推进最先进的作用，并有可能影响其他学科。