Short Term Variation in Mass Flux During Basaltic Eruptions

Harris和FlynnEAR-0106349已经证明，在喷流的玄武岩喷发期间，质量通量速率在逐个月的长时间内发生变化。这些变化提供了对喷发机制的洞察，揭示了洞穴是否被加压。然而，几乎没有数据来确定质量通量在几秒到几小时的时间尺度上是如何变化的。这样的数据将提供对火山喷发期间供应变化的洞察。近年来，收集到的未公布的数据表明，喷发的质量通量在几分钟的时间内可能在高水平和低水平之间变化。如果存在这种短期的周期性，那么这一发现将为持续的玄武岩喷发在几分钟到几个小时的长时间内供应的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，首次确定可能存在的短期质量通量的旋回性。这将为我们提供对持续喷发期间供应机制的洞察，回答主要问题：供应是稳定的还是激增的？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，我们选择了两座火山进行分析：基拉韦厄火山(夏威夷)和维拉里卡火山(智利)。虽然基拉韦厄火山的活动主要是管状熔岩流的侵位，但维拉里卡拥有一个持续活跃的熔岩湖。在这两座火山，初步数据表明，向喷发地供应的岩浆可能在高水平和低水平之间循环，每个周期持续几分钟到几个小时。在每座火山，都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，沿着活跃的主管的天窗和喷发地点上方的白炽灯喷口将每隔1-2秒进行一次温度测量。在维拉里卡，在两个现场活动期间，将同时收集热数据和气体流量和地震数据。将对结果进行关联和分析，以寻找向维拉里卡熔岩湖循环供应的证据。在这两个目标，每天收集的卫星温度数据将被用来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。这些多项地球物理测量的数据集将使管道对流和脱气模型能够适用于每个系统。这项研究将通过扩展关于火山喷发如何在短时间内演变的知识，促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，这些模型根据挥发分变化和/或对流翻转来预测和解释这种短期变化。我们将使用这些数据以三种方式支持教育/外展项目。(1)我们会把资料放在互联网上，供公众查阅。(2)我们将利用这些数据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)通过夏威夷太空助学金联盟的支持，本科生将受益于使用数据支持他们的工作。

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 Over recent years unpublished data have been gathered indicating that erupted mass fluxes may vary between high and low levels over minute-long periods.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