CAREER: Detailed distributions of tephra fall characteristics: insights into magma fragmentation and transport via volcanic plumes

火山爆发产生的火山灰云可以延伸到几英里外的大气层。这些羽流是影响最深远的火山灾害。它们会造成人员伤亡，扰乱空中交通、全球经济和气候。火山灰的特性控制着它的移动距离以及它落在地面上的时间和地点。因此，量化火山灰的特征对于理解、预测和模拟火山羽流是至关重要的。这对于警告可能受影响的地区和减少火山喷发的影响至关重要。这项研究项目旨在澄清火山灰和喷发过程之间的联系。它将结合传统和新的技术，并使用美国瀑布喷发作为案例研究。灰尘输送模型将综合这一项目的成果。这将提高灰云预报的精度和准确度。该教育项目将提高高中生对火山喷发和沉积的认识。它将专注于俄勒冈州和华盛顿州农村和部落地区的高中。学生们将通过动手活动了解自家后院的火山矿床。他们将通过演讲与当地社区分享他们的新知识。该项目最终旨在提高高中生对STEM教育和科学研究的兴趣。由于导致火山喷发形成和扩散的过程具有地下性质，我们对火山喷发机制的了解主要依赖于对火山喷发后收集的火山喷发特征的解释。形态和结构研究目前集中在有限数量的分析参数、碎屑大小和/或采样位置，因此无法完全捕捉到特弗拉矿床的复杂性。该项目将通过以下方式解决这些限制：1)评估二次破碎的重要性，这将导致在管道中最初形成的Tephra的大小和形状发生变化；2)改进Tephra传输和沉积模型；以及3)简化和标准化对Tephra物理特性的分析。将火山灰的最终特征与火山管道中初级破碎产物的特征进行比较，将确定喷发期间发生的次级破碎的数量及其对羽流高度的控制。对比大小数量级的喷发和质量排放率之间的特征将增强我们对喷发参数和喷发产物之间联系的了解，并勾勒出新的战略来量化喷发源参数，这是预测和模拟羽流行为所必需的。解释颗粒大小、密度和组分分布的横向变化将有助于破译颗粒聚集和漂流等传输过程。将结果直接应用到现有的火山灰输送和沉积数值模型中，将改善对火山灰云和随后的火山灰坠落的预测。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。

Explosive volcanic eruptions produce ash clouds that can reach miles into the atmosphere. These plumes are the most far reaching of volcanic hazards. They can cause fatalities and disrupt air traffic, the global economy, and the climate. The characteristics of the ash control how far it travels and when and where it falls on the ground. Quantifying ash characteristics is thus crucial to understand, predict, and model volcanic plumes. This is central to warn likely affected areas and reduce impacts from eruptions. This research project aims at clarifying the links between ash and eruptive processes. It will combine traditional and new techniques and use eruptions in the US Cascades as case studies. Models of ash transport will integrate the results of this project. It will increase the precision and accuracy of ash cloud forecasting. The educational project will raise awareness among high-schoolers of volcanic eruptions and deposits. It will focus on high schools in rural and tribal areas in Oregon and Washington. Students will learn about volcanic deposits in their backyard via hands-on activities. They will share their new knowledge with their local community via a presentation. The project ultimately aims at raising high schoolers interest in STEM education and scientific research.Because of the subterraneous nature of the processes leading up to tephra formation and dispersal, our knowledge of eruptive mechanisms mostly relies on the interpretation of tephra characteristics collected after the eruption. Morphological and textural studies currently focus on a limited number of parameters analyzed, clast sizes, and/or sampling locations, thus preventing a full capture of the complexity of tephra deposits. This project will address these limitations by 1) assessing the importance of secondary fragmentation, which leads to a change of the size and shape of tephra after their initial formation in the conduit; 2) improving Tephra Transport and Deposition Models; and 3) streamlining and standardizing the analysis of tephra physical characteristics. Comparing tephra final characteristics with those of the products of primary fragmentation in the conduit of the volcano will establish the amount of secondary fragmentation occurring during the eruption and its control on plume height. Contrasting characteristics between eruptions spanning orders of magnitude in volume and mass discharge rate will enhance our knowledge of the links between eruptive parameters and eruptive products and outline new strategies to quantify eruption source parameters indispensable to predict and model plume behavior. Interpreting lateral variations in size, density, and componentry distributions will help decipher transport processes such as particle aggregation and rafting. Direct implementation of results into existing numerical models of tephra transport and sedimentation will improve forecast of volcanic ash cloud and ensuing tephra fall.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.