Collaborative Proposal: Ash Particles and the Bubbles that Make Them: Measuring Bubble Size from Ash Fragments for New Insights Regarding Eruption Dynamics

合作提案：火山灰颗粒和形成它们的气泡：测量火山灰碎片的气泡尺寸以获得有关喷发动力学的新见解

• 批准号: 0838292
• 负责人: Alexander Proussevitch
• 金额: $ 45.37万
• 依托单位: University of New Hampshire
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0838292&HistoricalAwards=false
• 关键词: Collaborative; Proposal; Ash; Particles; Bubbles

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Explosive volcanic eruptions are driven by the rapid growth of gas bubbles in magma that burst in the eruption column as they rapidly expand. By measuring the size of these bubbles just before they burst, it is possible to explore the processes that culminate in dangerous, explosive eruptions. However, it is impossible to monitor the interior of an exploding eruption column at the level of detail required, and by the time the final volcanic product of ash is observable, the bubbles that drove the eruption have already burst. Consequently, it is necessary to examine the surfaces of individual ash particles to analyze the imprints that these exploding bubbles have left on ash surfaces. This project is directed to developing a technique to determine the size distribution of these bubbles, and thus shed light on the processes of vesiculation and disruption immediately prior to fragmentation during explosion. Bubble sizes can be measured on the basis of the radius of curvature of concavities on the surfaces of ash particles. These ash particles would have been the remnants of inter-bubble films and Plateau borders that existed prior to the fragmentation of the erupting magmatic foam, so should preserve information about the bubbles that separated them. Bubble fragment curvature can be constructed using digital elevation maps for individual ash fragments derived from Stereo-Scanning Electron Microscopy (SSEM). 3D shapes and bubble volumes can then be reconstructed from the imprinted curvatures in orthogonal cross sections of bubble "craters." This way, it is possible to determine bubble size, even when the expanding bubbles have burst during eruption (fragmentation). The technique developed in this project will be applied to natural ashes from recent eruptions of Fuego, Mt. Spurr, and Mt. St. Helens volcanoes, and the relations between bubble size distributions (BSD), bubble number densities (BND), and ash particle size distributions (PSD) will be quantified. This will make it possible to test a number of scientific hypotheses that can determine the relations between magma vesiculation dynamics of energetic volcanic eruptions and their products. It is expected that this study will result in new volcanic product analysis tools available for the broader community of volcanologists for application to, among others, pre-fragmentation vesiculation in ashes from highly energetic volcanic eruptions; hazard assessment of past and future eruptions; and stratospheric ash and its climate implications.

该奖项是根据2009年《美国复苏与再投资法》（公法111-5）资助的。爆炸性的火山喷发是由岩浆中气泡快速生长的驱动的，岩浆迅速扩展时喷发柱中破裂。通过在这些气泡破裂之前测量这些气泡的大小，可以探索在危险，爆炸性喷发中达到高潮的过程。但是，不可能以所需的细节级别监视爆炸式喷发柱的内部，到可观察到的灰的最终火山产品时，驱动喷发的气泡已经破裂。因此，有必要检查单个灰分颗粒的表面，以分析这些爆炸气泡在灰烬表面上留下的烙印。该项目用于开发一种技术来确定这些气泡的尺寸分布，因此在爆炸过程中碎裂之前立即阐明了囊泡和破坏过程。可以根据灰分表面上凹入的曲率半径来测量气泡尺寸。这些灰分颗粒本来是在爆发的岩浆泡沫破裂之前存在的泡沫间膜和高原边界的残余物，因此应保留有关将它们分开的气泡的信息。可以使用来自立体扫描电子显微镜（SSEM）的单个烟灰片段的数字高程图来构建气泡碎片曲率。然后可以从气泡“陨石坑”的正交横截面中的印迹曲线中重建3D形状和气泡量。这样，即使在喷发过程中膨胀的气泡破裂（碎片），也可以确定气泡尺寸。该项目开发的技术将适用于Fuego，Spurr和St. Helens火山的最近喷发的天然灰烬，以及气泡尺寸分布（BSD），气泡数密度（BND）和Ash Ash的关系之间的关系粒度分布（PSD）将被量化。这将使可以测试许多科学假设，这些假设可以确定能量火山喷发及其产物的岩浆囊泡动力学之间的关系。可以预期，这项研究将为更广泛的火山学家社区提供新的火山产品分析工具，以应用于高能火山喷发的灰烬前裂缝前的泡沫；对过去和未来喷发的危害评估；和平流层灰及其气候的影响。