Mount Erebus Volcano Observatory: Gas Emissions and Seismic Studies

该奖项由极地项目办公室的南极地质和地球物理项目提供，支持对南极洲最活跃的火山埃里伯斯火山（罗斯岛）的火山活动进行研究。埃里伯斯火山的独特之处在于，它的山顶火山口有一个由熔融二氧化硅和富含碱的声母岩岩浆组成的持久对流湖。埃里伯斯火山是世界上为数不多的几个表现出几乎连续的小型爆炸活动和内部地震活动的火山之一。它是一个理想的自然实验室，可以研究岩浆如何释放气体以及与岩浆对流管道有关的地震。该项目的主要目标是利用地震研究和气体排放率测量相结合的方法，更好地了解岩浆管道系统的性质和动力学，以及熔岩湖的喷发和脱气。气体研究的目的是：1)研究埃里伯斯作为气体和气溶胶来源对南极环境的作用；2)了解火山活动作为二氧化碳排放到大气的来源的作用，特别是对于高碱性岩浆；3)了解埃里伯斯岩浆系统中主要挥发物（水蒸气、二氧化碳、总硫、氟和氯）的演化及其在埃里伯斯喷发行为中的作用；4)将气体排放的性质与观测到的地震活动联系起来。一项高度优先的工作将是测量烟柱中的二氧化碳排放率，并确定土壤气体中的二氧化碳通量。对二氧化碳排放的测量将提供有关高碱性岩浆系统中二氧化碳脱气的第一批可用数据。将作出特别努力来测量铅排放率，以评价埃里伯斯山的铅相对于海洋气溶胶的贡献和南极东部冰盖上的雪的贡献，并相对于铅的人为起源假设来评价这些来源。埃里伯斯上现有的10个短周期地震台站网络提供每日、触发和连续的数字数据，这些数据是日常观测业务的支柱，并为研究火山系统的各个方面提供了重要的积累事件基础。该项目将采取三种具体的火山地震调查途径：1)在阵列中增加一个永久宽带地震站并更新现有的数据采集系统；2)部署一个临时宽带站网络，以增强先前试点研究的结果；3)扩大现有软件的开发，以实现地震发生的自动精确定时，从而确定精确的位置。这样就可以精确地收集地震资料，用于火山内部的计算机模型。它还将为一般火山学界提供一种工具，用于火山监测和监测火山内部活动的细微变化，并协助监测喷发危险。利用宽带数据，该项目计划a)对爆炸机制进行详细研究，并进一步调查与爆炸相关的长周期信号，b)寻找地震机制的时空变异性，更好地了解地震活动与气体排放变化的关系。

This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports research to study the volcanism at Mount Erebus (on Ross Island), Antarctica's most active volcano. Mount Erebus is unique in hosting in its summit crater a persistent convecting lake of molten silica and alkali-rich phonolitic magma. Erebus is one of only a handful of volcanoes worldwide that exhibit nearly continuous small explosive activity and internal earthquake (seismic) activity. It is an ideal natural laboratory to study how gas is given off by magma and the earthquakes associated with a convecting magma conduit. The principal objective of this project is to better understand the nature and dynamics of the magmatic plumbing system, and eruptions and degassing from the lava lake using a combination of seismic studies and gas emission rate measurements.The gas studies are designed: 1) to examine the role of Erebus as a source of gas and aerosols to the Antarctic environment; 2) to understand the role of volcanism as a source of carbon dioxide emissions to the atmosphere, especially for a highly alkalic magma; 3) to understand the evolution of the main volatiles (water vapor, carbon dioxide, total sulfur, fluorine and chlorine) in the Erebus magmatic system and their role in the eruptive behavior of Erebus; and 4) to correlate the nature of the gas emissions with the observed seismic activity. A high priority will be to measure carbon dioxide emission rates in the plume and to determine soil gas carbon dioxide fluxes. The measurements of carbon dioxide emissions will provide some of the first available data on carbon dioxide degassing from a highly alkalic magma system. A special effort to measure lead emission rates will be made to evaluate the contribution of lead from Mount Erebus, relative to contributions from marine aerosols, to snow on the East Antarctic Ice Sheet and to evaluate these sources relative to hypotheses of anthropogenic origins of lead.An existing network of ten short-period seismic stations on Erebus provides daily, triggered and continuous digital data which are the backbone of routine observatory operations and are providing an important and accumulating base of events with which to investigate various aspects of the volcanic system. This project will undertake three specific avenues of seismic investigation of the volcano: 1) add a permanent broadband seismic station to the array and update the present data acquisition system; 2) deploy a temporary network of broadband stations to augment the results of a previous pilot study; and 3) expand development of current software to allow automatic and precise timing of earthquake occurrences and thus allow precise locations to be determined. This will permit refined collection of earthquakes for use in a computer model of the interior of the volcano. It will also provide a tool for the general volcanological community to use for volcano surveillance and for monitoring subtle changes in the internal behavior of a volcano and assist with eruption hazard monitoring. Using broadband data, this project plans to a) undertake a detailed study of the explosion mechanism and further investigate the very-long-period signals associated with explosions, and b) look for temporal and spatial variability in earthquake mechanisms and better understand seismic activity with respect to variations in gas emissions.