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

正如2010年冰岛埃亚菲亚德拉火山喷发所见证的那样，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，由于这些火山爆发经常发生在偏远、难以到达的地方，我们并不完全了解许多可能产生冰川火山危害的过程，比如洪水和泥石流。为了更好地理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产物之一，称为“枕状熔岩”。虽然枕状熔岩是海底最常见的熔岩之一，覆盖了地球表面的70%，但它们在冰下的形成相对来说还没有被研究过。我们将在冰岛和加拿大不列颠哥伦比亚省的两个地区进行研究，这些地区的冰川火山枕状熔岩的暴露程度非常高。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是如何从熔岩转移到水和冰的，这可能会带来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，我们也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海底的形成，这可能对未来的矿物和能源资源很重要。本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关于冰下枕丘形成的假设，包括在一个不断增长的枕状火山中熔岩运输的模型，以及爆炸性和喷涌式喷发风格之间突然转变的可能性。具体来说，我们将解决以下问题：i)枕状熔岩就位的开始是否先于爆炸阶段？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)在一次喷发期间，沿裂缝段是否有多个喷发中心活跃？我们将通过使用现代现场和分析技术来记录两个不同枕脊的三维结构、地层学和地球化学，并进行特殊暴露：(1)冰岛西南部雷克雅内斯半岛沿单个裂缝段的露天采石场，(2)不列颠哥伦比亚省北部枕脊的顶部。这两个地点都有相似的岩相，包括一个特定的玻璃凝灰岩角砾岩层序，由岩脉切割而成，这些岩脉为紧靠凝灰岩角砾岩上方的枕状熔岩流提供食物（TDP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组成，与PIs充分合作，建立一个冰下枕头特征的综合数据库，用于与其他环境中产生的枕头熔岩进行比较，并有可能修改冰下火山枕头主导部分的现有模型。

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.