Short Term Variation in Mass Flux During Basaltic Eruptions

玄武岩喷发期间质量通量的短期变化

• 批准号: 0106349
• 负责人: Andrew J. Harris
• 金额: $ 14.89万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-07-01 至 2005-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0106349&HistoricalAwards=false
• 关键词: Short; Term; Variation; Mass; Flux

Harris and FlynnEAR-0106349Mass flux rates have been shown to vary over day-to-month long periods during effusive basaltic eruptions. These variations provide insights into eruption mechanisms, revealing whether or not the chamber was pressurized. Little data exist, however, to determine how mass fluxes vary over time scales of seconds to hours. Such data would provide insight into the variability of supply during an eruption. Over recent years unpublished data have been gathered indicating that erupted mass fluxes may vary between high and low levels over minute-long periods. If such short term cyclicity exists, then this finding will provide unique insights into the stability of supply to persistent basaltic eruptions over minute to hour long periods. The objective of this research is thus to search for and examine short term mass flux variations during ongoing basaltic eruptions defining, for the first time, any cyclicity in the short term mass flux that may exist. This will provide us insights into the supply mechanism during persistent effusive eruptions, answering the prime question: is supply steady or surging? This in turn will allow us to apply conduit convection models that explain the relevant supply mode.To achieve these objectives, two volcanoes characterized by contrasting styles of persistent activity have been selected for analysis: Kilauea (Hawai'i) and Villarrica (Chile). While activity at Kilauea is dominated by the emplacement of tube-fed lava flows, Villarrica hosts a persistently active lava lake. At both of these volcanoes, preliminary data indicate that magma supply to the eruption site may cycle between high and low levels, with each cycle lasting minutes to hours. At each volcano data sets capable of revealing short term mass flux variation will be collected. At Kilauea, thermal measurements will be made every 1-2 seconds at skylights along the active master tube and at incandescent vents over the eruption site. At Villarrica, during two field campaigns, thermal data will be collected simultaneously with gas flux and seismic data. Results will be correlated and analyzed for evidence of cyclic supply to Villarrica's lava lake. At both targets, satellite thermal data collected on a daily basis will be used to construct longer mass flux time series allowing the persistence of any cyclic behavior to be examined. These data sets of multiple geophysical measurements will allow conduit convection and degassing models to be fitted to each system. This research will advance our scientific understanding of persistently erupting systems by extending knowledge of how volcanic eruptions evolve over short time periods. We will also assess the validity of popular gas-based conduit convection models that predict and explain such short term variation in terms of variable volatile content and/or convective overturn. We will use these data to support educational/outreach projects in 3 ways. (1) We will make the data available on the Internet for public access. (2) We will use these data to support University of Hawai'i courses for teachers, allowing them to develop exciting high school lesson plans using real-time data. (3) Through the support of Hawai'i Space Grant Consortium undergraduate students will benefit by using the data to support their work.

Harris 和 FlynnEAR-0106349 已证明，在玄武岩喷发期间，质量通量率会逐日变化。 这些变化提供了对喷发机制的深入了解，揭示了火山室是否加压。 然而，很少有数据可以确定质量通量如何随秒到小时的时间尺度变化。 这些数据将有助于深入了解火山喷发期间的供应变化。 近年来，收集到的未发表的数据表明，在长达一分钟的时间内，喷发的质量通量可能在高水平和低水平之间变化。 如果存在这种短期周期性，那么这一发现将为了解持续玄武岩喷发在几分钟到几小时的长时间内的供应稳定性提供独特的见解。 因此，这项研究的目的是寻找和检查正在进行的玄武岩喷发期间的短期质量通量变化，首次定义可能存在的短期质量通量的任何周期性。 这将使我们深入了解持续喷发期间的供应机制，回答首要问题：供应是稳定还是激增？ 这反过来将使我们能够应用管道对流模型来解释相关的供应模式。为了实现这些目标，选择了两座具有对比鲜明的持续活动风格的火山进行分析：基拉韦厄火山（夏威夷）和比亚里卡（智利）。基拉韦厄火山的活动主要是管式熔岩流的形成，而比亚里卡则拥有一个持续活跃的熔岩湖。 在这两座火山中，初步数据表明，喷发地点的岩浆供应可能会在高水平和低水平之间循环，每个周期持续几分钟到几小时。 在每个火山，将收集能够揭示短期质量通量变化的数据集。 在基拉韦厄火山，每隔 1-2 秒就会在活动主管沿线的天窗和喷发地点上方的白炽通风口进行热测量。在比亚里卡，在两次现场活动中，热数据将与气体通量和地震数据同时收集。 结果将被关联和分析，以作为比亚里卡熔岩湖循环供应的证据。 在这两个目标上，每天收集的卫星热数据将用于构建更长的质量通量时间序列，以便检查任何循环行为的持续性。 这些多个地球物理测量的数据集将允许管道对流和脱气模型适合每个系统。这项研究将通过扩展对火山喷发在短时间内如何演变的了解，增进我们对持续喷发系统的科学理解。 我们还将评估流行的基于气体的管道对流模型的有效性，该模型可以预测和解释可变挥发物含量和/或对流翻转方面的短期变化。 我们将使用这些数据以三种方式支持教育/推广项目。 (1) 我们将在互联网上提供数据以供公众访问。 (2) 我们将使用这些数据来支持夏威夷大学的教师课程，使他们能够利用实时数据制定令人兴奋的高中课程计划。 (3) 通过夏威夷太空资助联盟的支持，本科生将受益于使用这些数据来支持他们的工作。