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

职业：火山灰坠落特征的详细分布：深入了解岩浆破碎和通过火山羽流的输送

• 批准号: 2240044
• 负责人: Thomas Giachetti
• 金额: $ 75.27万
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-02-01 至 2028-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2240044&HistoricalAwards=false
• 关键词: CAREER; Detailed; distributions; tephra; fall

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.

火山爆发产生的火山灰云可以到达几英里外的大气层。这些羽流是影响最深远的火山危害。它们会造成死亡，扰乱空中交通、全球经济和气候。火山灰的特性决定了它移动的距离以及何时何地落在地面上。因此，量化火山灰特征对于理解、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喷发的影响至关重要。这个研究项目的目的是澄清火山灰和喷发过程之间的联系。它将结合传统和新技术，并以美国喀斯喀特山脉的火山喷发为案例研究。灰输运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喷发和沉积物的认识。它将重点关注俄勒冈州和华盛顿州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。由于导致热毯形成和扩散过程的地下性质，我们对喷发机制的了解主要依赖于对喷发后收集的热毯特征的解释。形态学和质地研究目前集中在有限数量的分析参数、碎屑大小和/或采样位置上，因此无法完全捕捉到麻黄沉积物的复杂性。该项目将通过以下方式解决这些限制：1)评估次生破碎的重要性，次生破碎会导致管道初始形成后管道大小和形状的变化；2)改进猪瘟输运和沉积模型；(3)精简和规范对麻药物理特性的分析。将火山导管中次生破碎的最终特征与次生破碎产物的特征进行比较，可以确定喷发过程中次生破碎的数量及其对烟羽高度的控制。对比火山喷发在体积和质量排放率上跨越数量级的特征，将增强我们对喷发参数和喷发产物之间联系的认识，并勾勒出量化喷发源参数的新策略，这些参数对于预测和模拟羽流行为是必不可少的。解释大小、密度和成分分布的横向变化将有助于解释颗粒聚集和漂流等运输过程。将结果直接应用于现有的火山灰移动和沉积数值模型，将改进对火山灰云和随后的火山灰坠落的预测。该奖项反映了美国国家科学基金会的法定使命，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。