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

爆炸性的火山爆发产生的灰云可以到达大气层几英里。这些烟羽是影响最深远的火山灾害。它们可能导致死亡，扰乱空中交通，全球经济和气候。火山灰的特性决定了它传播的距离以及它福尔斯何时何地落到地面。因此，量化火山灰的特征对于理解、预测和模拟火山羽流至关重要。这对于警告可能受影响的地区和减少火山爆发的影响至关重要。该研究项目旨在澄清火山灰与喷发过程之间的联系。它将结合联合收割机的传统和新技术，并使用在美国瀑布的爆发作为案例研究。灰的运输模型将整合该项目的结果。它将提高灰云预报的精度和准确性。该教育项目将提高高中生对火山爆发和沉积物的认识。它将集中在俄勒冈州和华盛顿的农村和部落地区的高中。学生将通过动手活动了解他们后院的火山沉积物。他们将通过演讲与当地社区分享他们的新知识。该项目的最终目的是提高高中生对STEM教育和科学研究的兴趣。由于火山喷发形成和扩散过程的潜在性质，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。形态和纹理的研究目前集中在有限数量的参数分析，碎屑大小，和/或采样位置，从而防止火山灰矿床的复杂性的全面捕获。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，这导致火山灰在管道中初始形成后大小和形状的变化; 2）改进火山灰运输和沉积模型; 3）简化和标准化火山灰物理特性的分析。比较火山灰的最终特征与在火山管道中的初级碎片的产物的特征，将确定在喷发期间发生的次级碎片的量及其对羽流高度的控制。火山爆发跨越数量级的体积和质量排放率之间的对比特性，将提高我们的知识之间的联系，喷发参数和喷发产品，并概述了新的战略，量化喷发源参数不可或缺的预测和建模羽流行为。解释横向变化的大小，密度和组分分布将有助于破译传输过程，如颗粒聚集和漂流。将结果直接应用到火山灰输送和沉积的现有数值模型中，将改善火山灰云和火山灰下落的预测。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值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.