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: 1220176
• 负责人: Meagen Pollock
• 金额: $ 12.69万
• 依托单位: College of Wooster
• 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=1220176&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Eyjafjallajokull喷发期间所目睹的那样，熔岩和冰之间的相互作用可能会对当地和全球产生毁灭性的影响。然而，由于这些喷发最经常发生在偏远、难以进入的地方，我们并不完全了解洪水和泥石流等迅速融化的冰可能造成冰川-火山危险的许多过程。为了更好地了解在冰内和冰下喷发期间熔岩流形成的作用，我们建议研究冰下喷发的一种产品，称为枕状熔岩。尽管枕状熔岩是海底最常见的熔岩类型之一，覆盖了地球表面的70%，但它们在冰下的形成相对较少被研究。我们将在冰岛和加拿大不列颠哥伦比亚省的冰川火山枕状熔岩异常暴露的两个地区开展工作。我们的工作将帮助其他科学家更好地了解在冰川火山喷发期间，热量是如何从熔岩转移到水和冰中的，这可能会导致更好的方法来预测熔岩-冰相互作用导致的洪水规模。通过我们的研究，我们还将更好地了解如何利用古代沉积物中的枕状熔岩来揭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海底的形成，这可能对未来的矿产和能源资源很重要。这项研究的主要目标是使用覆盖一系列玄武岩成分的枕状熔岩来测试有关冰下枕丘形成的假说，包括日益增长的枕状主导火山内熔岩运移的模型，以及爆炸性喷发和喷涌喷发风格之间突然转变的可能性。具体地说，我们将解决以下问题：i)枕状熔岩侵位的开始之前是否有爆炸阶段？ii)熔岩是如何沿山脊结构分布的？iii)冰下枕状喷发期间的渗出率是多少？iv)在单个喷发期间，多个喷发中心是否沿着裂隙段活跃？我们将通过使用现代野外和分析技术来记录两个不同枕脊的三维结构、地层和地球化学，以寻求这些问题的答案：(1)沿着冰岛西南部雷克扬尼斯半岛单一裂隙段的露天采石场；(2)不列颠哥伦比亚省北部枕脊的顶部。这两个地点具有相似的岩相，包括被岩脉切割的玻璃质凝灰岩-角砾岩的特定地层序列，这些岩脉为直接部署在凝灰岩-角砾岩之上的枕状熔岩流提供(TDP岩相组合)。我们已经建立了一个由美国、冰岛和加拿大的科学家组成的基础广泛的研究团队，与PI充分合作，以建立一个全面的冰下枕头特征数据库，以便与其他环境中生产的枕状熔岩进行比较，并可能修改现有的冰下火山以枕头为主的部分的建造模型。