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.

自然界中一些最具破坏性的力是一些最具破坏性的力，它们的火山碎片密度电流，火山灰和浮石的混合物（也称为pyoclasts）和气体。 40，000年前，意大利那不勒斯附近的Campi Flegrei爆发的Campanian Ignimbrite是来自地球上最年轻的真正大型碎屑密度电流之一。这些电流距离通风口80公里，摧毁了目前有超过400万人的地区。这些电流的传统型号假定它们的厚度可能为100米，但是我们过去的工作表明，坎帕尼亚电流在整个景观上移动，沿着整个景观的流动移动，高度超过了山脊，高1.5倍。这种出色的移动性使这种“扩展”的火山碎屑密度电流更加危险，损害降低了。这种稀释电流需要大量的气体，远远超过喷发前岩浆中溶解的量可以解释的。另外两个可能的来源是空气的夹带和火山中热热系统的水参与。该项目将确定电流涉及的岩浆，空气和水热系统的气体量。这些信息将用于更好地预测哪些火山可能会产生高度移动电流和设计危害图，以考虑到这一移动性。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亚利桑那大学从事该项目，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进行合作。该结果可用于危害评估和响应计划，包括那不勒斯的美国海军支援活动。最近对Campanian Ignimbrite（CI）的热磁化研究发现，即使在离通风口80 km的情况下，Emplacement的温度甚至高于580 OC。这限制了可以合并多少空气，但是，为了计算精确的数量，更好地了解岩浆温度，以及其他气体（例如岩浆气体和水热液）是否需要大量的气体。该项目将包括1）现场调查，以更好地表征CI地层以及远端和近端沉积物的链接，并定义火山事件的相对时间； 2）通过傅立叶变换红外（FTIR）光谱，离子探针和电子微型探针，通过熔融包含物和磷灰石微晶的融合物和磷灰石微晶的完整挥发性分析（H2O，CO2，S，F和CL）。在开放系统脱气过程中，反向计算的挥发性浓度是一种新技术，应该揭示有关Campanian Ignimbrite Magma历史的很多。 3）研究以不同的应变率和残留水含量的方式研究玻璃过渡温度，以更好地定义安置温度。当前的模型和数据集的解释可能需要修改，以包括水热流体在“增压”喷发中的潜在作用，因为在许多气体的质量测量中，水热水都不会出现。 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.