权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

NSFGEO-NERC: Physical and Chemical Constraints on Large-volume Pyroclastic Blasts: The Campanian Ignimbrite Eruption, Italy

NSFGEO-NERC：大体积火山碎屑爆炸的物理和化学约束：意大利坎帕尼亚火熔岩喷发

基本信息

批准号：
1761713
负责人：
Michael Ort
金额：
$ 29.07万
依托单位：
Northern Arizona University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-04-01 至 2022-03-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1761713&HistoricalAwards=false
关键词：
NSFGEO NERC Physical Chemical Constraints

项目摘要

Pyroclastic density currents, mixtures of volcanic ash and pumice (also known as pyroclasts) and gas that move at high rates of speed, are some of the most destructive forces in nature. The Campanian Ignimbrite, which erupted from the Campi Flegrei near Naples, Italy, 40,000 years ago, is the deposit from one of the youngest truly large pyroclastic density currents on Earth. The currents reached over 80 km from the vent and devastated an area currently occupied by more than 4 million people. Traditional models for these currents assume they are tens to perhaps 100 meters thick, but our past work shows the Campanian current moved as a kilometer-thick flow across the landscape, overtopping ridges 1.5 times that height. This great mobility makes this sort of "expanded" pyroclastic density current much more hazardous and the damage less predictable. This dilute current required an enormous amount of gas, more than can be explained by the amount dissolved in the magma prior to eruption. Two other possible sources are the entrainment of air and the involvement of water from a hot hydrothermal system within the volcano. This project will determine the amounts of gas from the magma, air, and hydrothermal system involved in the current. This information will be used to make better predictions of which volcanoes might produce highly mobile currents and design hazards maps that take this mobility into account. Two undergraduate students, two graduate students, a post-doctoral researcher, and a professor will work on this project at Northern Arizona University and a graduate student and a professor will work at Oxford University. Three Italian researchers will also collaborate in this project. The results may be used for hazards assessments and response plans, including for the US Naval Support Activity in Naples.A recent thermal magnetization study of the Campanian Ignimbrite (CI) found the temperature of emplacement was above 580 oC even at 80 km from the vent. This limits how much air could have been incorporated, but, to calculate precise quantities, a better knowledge of the magmatic temperature and whether other sources of gas, such as magmatic gas and hydrothermal fluids, were significant, is needed. This project will include 1) field investigations to better characterize the CI stratigraphy and link distal and proximal deposits and define the relative timing of volcanic events; 2) complete volatile analysis (H2O, CO2, S, F and Cl) of melt inclusions and apatite microphenocrysts via Fourier Transform Infrared (FTIR) spectroscopy, ion probe, and electron microprobe. Back-calculating volatile concentrations during open-system degassing is a new technique that should reveal much about the Campanian Ignimbrite magma history; and 3) a study of the glass transition temperature at varying strain rates and residual water contents to better define the emplacement temperature. Current models and interpretations of datasets may need to be modified to include the potential role of hydrothermal fluids in "supercharging" an eruption, as hydrothermal water does not appear in many petrologic measurements of gases. A model for explosive eruptions that includes the potential contribution of erupted hydrothermal systems will help define volcanic hazards more accurately and may elucidate a possible cause for paroxysmal pyroclastic density current-producing eruptions.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.

火山碎屑密度流，火山灰和浮石（也称为火山碎屑）的混合物以及高速移动的气体，是自然界中最具破坏性的力量。坎帕尼亚火山灰岩，4万年前从意大利那不勒斯附近的Campi Flegrei喷发出来，是地球上最年轻的真正的大型火山碎屑密度流之一的存款。洋流到达距离喷口80多公里的地方，摧毁了目前居住着400多万人的地区。这些洋流的传统模型假设它们有几十到100米厚，但我们过去的工作表明，坎帕尼亚洋流以更厚的水流穿过地貌，超过山脊1.5倍的高度。这种巨大的流动性使得这种“扩大的”火山碎屑密度流更加危险，破坏更难以预测。这种稀释的气流需要大量的气体，超过了喷发前溶解在岩浆中的气体量。其他两个可能的来源是空气的夹带和火山内热液系统的水的参与。该项目将确定岩浆，空气和热液系统中涉及的气体量。这些信息将用于更好地预测哪些火山可能产生高度移动的电流，并设计考虑到这种流动性的危险地图。两名本科生、两名研究生、一名博士后研究员和一名教授将在北方亚利桑那大学从事这一项目，一名研究生和一名教授将在牛津大学工作。三名意大利研究人员也将在该项目中合作。研究结果可用于灾害评估和响应计划，包括美国海军在那不勒斯的支持活动。最近对坎帕尼亚火山灰岩（CI）的热磁化研究发现，即使在距离喷口80 km处，炮台温度也超过580 oC。这就限制了空气的含量，但是为了计算精确的数量，需要更好地了解岩浆温度以及其他气体来源，如岩浆气体和热液流体，是否重要。该项目将包括1）实地调查，以更好地表征CI地层，连接远端和近端沉积物，并确定火山事件的相对时间; 2）通过傅立叶变换红外（FTIR）光谱，离子探针和电子显微探针对熔融包裹体和磷灰石微斑晶进行完整的挥发性分析（H2O，CO2，S，F和Cl）。反算开放系统脱气过程中的挥发分浓度是一种新技术，应揭示更多关于坎帕尼亚火山灰岩岩浆的历史;和3）在不同的应变速率和残余水含量的玻璃化转变温度的研究，以更好地确定侵位温度。目前的模型和数据集的解释可能需要修改，以包括热液流体在“增压”喷发的潜在作用，因为热液水没有出现在许多气体的岩石学测量。爆炸性喷发的模型，包括潜在的贡献喷发的热液系统将有助于更准确地确定火山灾害，并可能阐明一个可能的原因，阵发性火山碎屑密度电流产生的eruptions.This奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。