Collaborative Research: An Integrated Study of Silicic Lava Emplacement

了解熔岩流的持续时间和速度是火山灾害管理和风险评估的核心。对持续喷发的火山如基拉韦厄火山（夏威夷）和埃特纳火山（西西里）的多年观察，已经对玄武岩熔岩流有了深入的了解;然而，对其他类型的熔岩缺乏类似的了解。在地质记录中，粘性熔岩的喷发很常见，但在人类的时间尺度上却很少见。因此，对活跃的熔岩及其行为的观察非常有限。2000年代在智利发生的两次被称为流纹岩的特别粘稠的熔岩喷发，使得人们首次实时观察到流纹岩熔岩喷发。这些观察结果导致火山科学家需要重新研究熔岩流动的方式，因为它们被认为比预期的更快，流动时间更长。在这项研究中，两个非常年轻的流纹岩熔岩流在加州将是一个详细的研究，其中他们的内部和外部结构和冷却历史将被检查，以更好地了解他们如何流动，多久，多快的重点。结果将适用于未来的流纹岩熔岩在东部加州，俄勒冈州，黄石国家公园，和世界各地的其他地方的爆发。黑曜石圆顶和南古力熔岩将是重点外源和内源性的增长模式，使用结构体系结构和应变，热，流变梯度模式。研究人员将使用LiDAR数据和三维结构分析编制详细的形态图，这些分析使用了现场的宏观特征和微观应变研究。这些分析将描述和量化熔岩在喷发和就位的各个阶段不同部分的应变类型和强度。应变数据集将与球晶和差示扫描量热法的冷却速率分析结果相结合，以限制侵位时间尺度。流变学实验将量化由于晶体、气泡和溶解水含量的变化而引起的有效粘度的变化。这些数据将共同产生一个全面的结构和热流变模型，描述了火山熔岩从喷发到停止，以及从喷口到边缘的流动。

Understanding the duration and speed of lava flows is central to volcanic hazard management and risk assessment. Years of observations at persistently erupting volcanoes like Kilauea (Hawaii) and Etna (Sicily) have produced a sophisticated understanding of basaltic lava flows; however, a similar level of understanding is absent for other types of lava. Eruptions of viscous, silicic lavas are common in the geological record but are infrequent at human timescales. Observations of active silicic lavas and their behavior are thus very limited. Two eruptions of a particularly viscous lava called rhyolite in the 2000s in Chile, allowed the first real-time observations of rhyolite lava eruptions. Those observations have led to the need for volcano scientists to re-examine the ways that silicic lavas flow because they were seen to be faster and flow for longer durations than anticipated. In this study, two very young rhyolite lava flows in California will be the focus of a detailed study in which their internal and external structures and cooling history will be examined in order to better understand how they flowed, for how long, and how fast. The results will be applicable to future eruptions of rhyolite lava in eastern California, Oregon, at Yellowstone National Park, and elsewhere around the world.Obsidian Dome and South Coulee lavas will be the focus for exogenous and endogenous growth patterns using structural architecture and strain, thermal, and rheological gradient patterns. The researchers will compile a detailed morphological map using LiDAR data and three-dimensional structural analyses using macroscopic features in the field and microscopic strain studies. The analyses will characterize and quantify the types and magnitudes of strain active in different parts of the lavas throughout stages of their eruption and emplacement. Strain datasets will then be integrated with the results of cooling rate analyses from spherulites and differential scanning calorimetry to constrain the emplacement timescales. Rheological experiments will quantify the variations in effective viscosity due to variations in crystal, bubble, and dissolved water contents. Together these data will produce a comprehensive structural and thermo-rheological model that describes the evolving flow of silicic lava from eruption to cessation, and from the vent to the margins.