Mechanisms and Dynamics of Magma-Water Interactions: Case Studies From Iceland

火山喷发涉及岩浆和外部水的相互作用，通常比不涉及外部水的类似岩浆喷发更具爆炸性。这种岩浆与水的相互作用给社会、农业和经济带来了巨大的风险，因为它们会产生大量细颗粒的火山灰，覆盖附近的人口中心，威胁牲畜，危及空中交通，2010年4月和2011年5月冰岛的火山爆发就证明了这一点。因此，了解岩浆-水相互作用的爆炸性是减轻潮湿环境中火山对社会的风险的关键。拟议中的研究将利用冰岛的一系列案例研究，提高我们对爆炸性喷发中水如何增强岩浆碎裂的理解，这些案例涉及不同数量的水。这项工作的成果将通过科学出版物和报告、培训新的火山学家骨干和制作一系列教育短片广泛传播，这些短片旨在激发9至12年级学生在科学探索和发现过程中的兴奋情绪。了解爆炸性岩浆-水的相互作用是复杂的，因为岩浆中含有气体，除了外部的水外，这些气体还参与了火山喷发的爆炸性。有人建议，通过比较没有岩浆气体参与的末元喷发类型（“无根火山锥”）的爆炸产物与冰岛火山喷发产生的火山灰，其中岩浆气体参与了破碎过程，以及在受控实验室条件下实验产生的颗粒，来解开岩浆气体和外部水的竞争影响。我们的比较将涉及颗粒形状，大小和密度分析，以量化水如何影响爆炸性。计算机模拟爆炸过程，结合颗粒尺度和沉积物尺度的测量，将使我们对岩浆-水相互作用的物理理解更加完善。通过我们的案例研究验证，该模型最终将用于预测爆炸性熔岩-水相互作用产生的火山灰扩散模式。拟议的工作将能够以一种以前不可能的方式量化外部水的作用，因此，它有可能影响此类火山爆发的危害评估和缓解战略。

Phreatomagmatic volcanic eruptions involve interactions between magma and external water and are typically more explosive than otherwise similar magmatic eruptions that do not involve external water. Such magma-water interactions pose significant risks to society, agriculture, and the economy because they generate large volumes of fine-grained ash that can blanket nearby population centers, threaten livestock, and endanger air traffic, as demonstrated by the April 2010 and May 2011 eruptions in Iceland. Understanding the explosivity of magma-water interactions, therefore, is key to mitigating risk to society from volcanoes in wet environments. The proposed research will advance our understanding of how water enhances magma fragmentation in an explosive eruption, using a suite of case studies from Iceland in which varying amounts of water were involved. The results of this work will be disseminated broadly, through scientific publications and presentations, training of a new cadre of volcanologists, and the production of a series of short educational films designed to stimulate excitement in the processes of scientific inquiry and discovery in students of grades 9-12.Understanding explosive magma-water interactions is complicated by the fact that the magma contains gases, which, in addition to external water, participate in driving the explosivity of the eruption. It is proposed to untangle the competing influences of magmatic gases and external water by comparing the explosive products of an end member eruption type ('rootless volcanic cones'), in which no magmatic gases participate, with ash from Icelandic eruptions in which magmatic gases were involved in the fragmentation process, and with particles produced experimentally under controlled laboratory conditions. Our comparisons will involve particle shape, size, and density analysis to quantify how water affects explosivity. Computer modeling of the explosion process, incorporating particle-scale and deposit-scale measurements, will allow refinement of our understanding of the physics of magma-water interactions. With validation using our case studies, the model will ultimately be useful for predicting patterns of ash dispersal from explosive lava-water interactions. The proposed work will allow quantification of the role of external water in a way that has not previously been possible, and as a consequence, it has the potential to impact hazards assessment and mitigation strategies for such eruptions.