Collaborative Research/RUI: Testing Hypotheses on Pillow Lava Production During Glaciovolcanic Eruptions

合作研究/RUI：检验冰川火山喷发期间枕状熔岩产生的假设

• 批准号: 1220403
• 负责人: Benjamin Edwards
• 金额: $ 16.16万
• 依托单位: Dickinson College
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-01 至 2016-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1220403&HistoricalAwards=false
• 关键词: Collaborative; Research; RUI; Testing; Hypotheses

As recently witnessed during the 2010 Eyjafjallajokull eruption in Iceland, interactions between lava and ice can have devastating local and global implications. However, because these eruptions most frequently occur in remote, hard-to-access places, we do not fully understand many of the processes that can produce glaciovolcanic hazards from rapidly melting ice, such as floods and mudflows. In order to better understand the role of lava flow formation during eruptions within and beneath ice, we propose to study one of the products of subglacial eruptions, called 'pillow lavas'. Although pillow lavas are one of the most common types of lavas on the ocean floor, which covers about 70 percent of Earth's surface, their formation beneath ice is relatively unstudied. We are going to work in two areas with exceptionally well-exposed examples of glaciovolcanic pillow lavas in Iceland and British Columbia, Canada. Our work will help other scientists to better understand how heat is transferred from lava to water and ice during glaciovolcanic eruptions, which may lead to better methods for predicting the sizes of floods resulting from lava-ice interactions. Through our research, we will also have a better understanding of how to use pillow lavas from ancient deposits to unravel mysteries related to ice-age global climate. Finally, we hope that our data will also be useful for better understanding of the formation of the Earth's ocean floors, which may be important for future mineral and energy resources. The main goals of this research are to use pillow lavas covering a range of basaltic compositions for testing hypotheses about the formation of subglacial pillow mounds, including models for lava transport within a growing pillow-dominated volcano and the potential for sudden transitions between explosive versus effusive eruption styles. Specifically we will address the following questions:i) Is the initiation of pillow lava emplacement preceded by an explosive phase?ii) How is lava distributed along and across the ridge structure?iii) What are effusion rates during subglacial, pillow-dominated eruptions?iv) Are multiple eruptive centers active along a fissure segment during a single eruptive episode? We will pursue answers to these questions by using modern field and analytical techniques to document the three-dimensional structure, stratigraphy and geochemistry of two different pillow ridges with exceptional exposures: (1) open-pit rock quarries along a single fissure segment on the Reykjanes Peninsula in southwestern Iceland and (2) the crest of Pillow Ridge in northern British Columbia. Both locations have similar lithofacies, including a specific stratigraphic sequence of vitric tuff-breccia cut by dikes that feed pillow lava flows emplaced immediately above the tuff-breccias (TDP lithofacies association). We have established a broad-based research team, comprising US, Icelandic and Canadian scientists working in full collaboration with the PIs, to build a comprehensive database of subglacial pillow characteristics for comparison to pillow lavas produced in other environments and potentially to revise existing models for the construction of the pillow-dominated parts of subglacial volcanoes.

正如最近在2010年冰岛埃亚菲亚德拉冰盖爆发期间所目睹的那样，熔岩和冰之间的相互作用可能对当地和全球产生毁灭性影响。然而，由于这些火山爆发最常发生在偏远、难以进入的地方，我们并不完全了解许多可能因快速融化的冰而产生冰川火山灾害的过程，如洪水和泥石流。为了更好地了解熔岩流形成的作用，在冰内和冰下的喷发，我们建议研究冰下喷发的产品之一，称为“枕状熔岩”。虽然枕状熔岩是海底最常见的熔岩类型之一，覆盖了大约70%的地球表面，但它们在冰下的形成相对未被研究。我们将在冰岛和加拿大的不列颠哥伦比亚省的两个地区开展工作，这两个地区都有非常好的暴露的冰川火山枕状熔岩。我们的工作将帮助其他科学家更好地了解冰川火山爆发期间热量如何从熔岩转移到水和冰，这可能会导致更好的方法来预测熔岩-冰相互作用造成的洪水规模。通过我们的研究，我们还将更好地了解如何利用来自古代沉积物的枕状熔岩来解开与冰河时代全球气候有关的谜团。最后，我们希望我们的数据也将有助于更好地了解地球洋底的形成，这对未来的矿物和能源资源可能是重要的。 本研究的主要目标是使用枕状熔岩覆盖一系列玄武岩成分测试有关冰下枕土丘形成的假设，包括模型内的一个不断增长的枕状为主的火山和潜在的爆发与喷发风格之间的突然转变的熔岩运输。具体来说，我们将解决以下问题：i）枕状熔岩侵位的启动之前，爆炸阶段？ii）熔岩是如何沿沿着和横跨山脊结构分布的？iii）冰下枕状喷发期间的渗出率是多少？iv）在一次喷发过程中，是否有多个喷发中心沿沿着裂隙段活动？我们将寻求这些问题的答案，通过使用现代的现场和分析技术，以文件的三维结构，地层学和地球化学的两个不同的枕岭具有特殊的曝光：（1）露天采石场沿着一个单一的裂缝段的雷克雅内斯半岛在冰岛西南部和（2）枕头岭的波峰在北方不列颠哥伦比亚省。这两个地点都有相似的岩相，包括由岩脉切割的玻质凝灰岩角砾岩的特定地层序列，这些岩脉为紧邻凝灰岩角砾岩上方的枕状熔岩流提供水源（SDP岩相组合）。我们已经建立了一个基础广泛的研究团队，由美国，冰岛和加拿大的科学家与PI充分合作，建立一个全面的冰下枕特征数据库，用于与其他环境中产生的枕熔岩进行比较，并可能修改现有的模型，用于建造冰下火山枕占主导地位的部分。