Short Term Variation in Mass Flux During Basaltic Eruptions

在玄武岩喷发期间，物质通量率在日-月的长时间内发生变化。这些变化提供了对喷发机制的见解，揭示了舱室是否加压。然而，几乎没有数据可以确定质量通量在秒到小时的时间尺度上是如何变化的。这些数据将有助于深入了解火山喷发期间供应的可变性。近年来收集到的未发表的数据表明，喷发的质量通量可能在几分钟内的高通量和低通量之间变化。如果存在这样的短期周期，那么这一发现将为持续几分钟到几小时的玄武岩喷发的供应稳定性提供独特的见解。因此，本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，首次确定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：供应是稳定的还是激增的？反过来，这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，选择了两个以持续活动的不同风格为特征的火山进行分析：基拉韦厄火山（夏威夷）和维拉里卡火山（智利）。基拉韦厄火山的活动主要是由管状熔岩流形成，而维拉里卡火山则有一个持续活跃的熔岩湖。在这两座火山上，初步数据表明，喷发地点的岩浆供应可能在高水平和低水平之间循环，每次循环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秒就会在活跃主管的天窗和喷发点上方的白炽灯通风口进行一次热测量。在Villarrica，在两次野外活动期间，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，作为维拉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久性。这些多重地球物理测量数据集将允许管道对流和脱气模型适用于每个系统。这项研究将通过扩展火山喷发如何在短时间内演变的知识，推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，该模型预测并解释了可变挥发性含量和/或对流翻转方面的这种短期变化。我们将通过三种方式使用这些数据来支持教育/推广项目。(1)我们将在互联网上提供数据，供公众查阅。(2)我们将使用这些数据来支持夏威夷大学的教师课程，使他们能够使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数据来支持他们的工作。

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 Over recent years unpublished data have been gathered indicating that erupted mass fluxes may vary between high and low levels over minute-long periods.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.