Investigating Submarine Basaltic Balloon Eruptions: Going to the Source

调查海底玄武岩气球喷发：追寻源头

• 批准号: 1332008
• 负责人: Steven Carey
• 金额: $ 2.56万
• 依托单位: University of Rhode Island
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-01 至 2016-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1332008&HistoricalAwards=false
• 关键词: Investigating; Submarine; Basaltic; Balloon; Eruptions

The majority of volcanic activity on Earth occurs beneath the sea yet the mechanisms of submarine eruptions remain poorly understood due to the lack of direct observations of the events and their products. One of the most peculiar and rarely observed submarine eruption styles is the production of giant gas-filled floating lava bombs from relatively shallow water eruptions of basaltic magma. These eruptions can pose hazards to ships at sea and to island and coastal communities due to the explosive release of gas and the high temperature of the magma. This research investigates shallow submarine volcanic eruptions that produce large floating scoria blocks, also known as lava balloons. The 1891 submarine eruption of Foerstner volcano off the northwest coast of Pantelleria island in the Mediterranean Sea will serve as a type example of this style of activity. High-resolution bathymetric mapping and video recording of the seafloor vent site and samples of rocks and volcanic sediments will be used in the analysis and are already in-hand from a previous oceanographic expedition. The mapping and video data will be used to create the first high-resolution geologic map of the vent area associated with this style of submarine volcanism. A major goal of the work will be to inform models of submarine explosive eruptions, which, at present, are immature compared to those for subaerial eruptions due to the lack of direct seafloor observations and paucity of studies on submarine deposits. Another objectiveis to address the fundamental problem of eruptive mechanisms via direct examination of the nature and morphology of the seafloor deposits left by the explosive Foerstner eruption. Major and trace element geochemical analyses of lava and volcaniclastic samples from the eruption will be carried out on bulk rock samples using XRF. The composition of associated quenched volcanic glass will be analyzed via electron microprobe. Data will be used to characterize the geochemical nature of the magma erupted and assess its volatile content and implications for eruptive mechanisms. Magma compositions at the vent site will be compared with samples of other submarine volcanic cones in the area to evaluate whether compositions can be used to fingerprint individual vents. Fourier transform infrared spectroscopy (FTIR) will be used to examine the composition of melt inclusions trapped in olivine and clinopyroxene crystals in order to determine pre-eruption magma gas (H2O and CO2) content and evaluate its role in driving the explosive nature of the eruption. The research will examine whether pre-concentration of volcanic gases in sub-seafloor conduits results in the build up of gas to levels that allow magma to inflate to the extent that it buoyantly rises to the sea surface. This research on the mechanisms of shallow water submarine explosive volcanism will allow for better assessment of its impacts on marine ecological disruptions and the acidification of local seawater. Broader impacts include undergraduate and graduate student support and development of educational modules used into university courses taught by the investigator, as well as support of an institution from an EPSCoR state.

地球上的大多数火山活动发生在海底，但由于缺乏对事件及其产物的直接观察，海底喷发的机制仍然知之甚少。海底喷发最奇特、最少见的喷发方式之一，是玄武岩岩浆在相对较浅的水面喷发，产生巨大的充气漂浮熔岩炸弹。由于天然气的爆炸性释放和岩浆的高温，这些喷发可能对海上船只以及岛屿和沿海社区构成危险。这项研究调查了浅层海底火山喷发，这些火山喷发产生了大型漂浮的珊瑚礁，也被称为熔岩气球。1891年地中海潘特莱里亚岛西北海岸附近的福斯特纳火山海底喷发将成为这种活动方式的典型例子。将在分析中使用海底喷口地点以及岩石和火山沉积物样本的高分辨率水深测绘和录像，并已从以前的海洋考察中获得这些资料。测绘和视频数据将用于绘制与这种类型的海底火山活动有关的喷口区域的第一张高分辨率地质图。这项工作的一个主要目标将是为海底爆炸模型提供信息，目前，由于缺乏对海底的直接观测和对海底沉积物的研究，与空中喷发相比，这一模型还不成熟。另一个目标是通过直接检查福斯特纳火山喷发留下的海底沉积物的性质和形态，解决喷发机制这一根本问题。将使用XRF对大量岩石样品进行熔岩和火山碎屑样品的常量元素和微量元素地球化学分析。将通过电子探针分析伴生的淬火火山玻璃的成分。将使用数据来描述喷发的岩浆的地球化学性质，并评估其挥发性含量和对喷发机制的影响。喷口现场的岩浆成分将与该地区其他海底火山锥的样本进行比较，以评估是否可以用岩浆成分来识别各个喷口。傅里叶变换红外光谱(FTIR)将被用来检测橄榄石和单斜辉石晶体中捕获的熔融包裹体的成分，以确定喷发前岩浆气体(H2O和CO2)的含量，并评估其在驱动喷发爆炸性方面的作用。这项研究将检验在海底管道中预先浓缩的火山气体是否会导致气体积聚到允许岩浆膨胀到浮升到海面的程度。对浅水海底爆发火山作用机理的研究将有助于更好地评估其对海洋生态破坏和当地海水酸化的影响。更广泛的影响包括本科生和研究生的支持，以及开发用于调查人员教授的大学课程的教育模块，以及来自EPSCoR州的机构的支持。