Lava Dome Collapses : Their Mechanisms and Short-Term Forecasting

熔岩穹顶是成堆的粘性岩浆，本质上是在火山喷口顶部形成球状塞子。随着部分凝固的岩浆沿着火山管道向上挤压，它们生长缓慢，当从岩浆中逸出的气体试图逃逸时，它们可以承受很高的内部压力。熔岩穹顶喷发是臭名昭著的，因为它们经常突然从友好的热情洋溢变成猛烈的爆炸性。一旦内部气体压力超过岩石的抗拉强度，这些塞子的突然拆除，无论是由于垂直驱动的爆炸，还是随着桩的生长和变得不稳定而突然坍塌和自发解体，都可能造成毁灭性的后果。这些坍塌事件产生了火山学中的主要危险之一-毁灭性的火山碎屑密度流，它们以高达60米/S的速度沿着火山侧翼流动。该项目涉及到改善对熔岩穹顶坍塌的理解和预测，并对几个正在进行的火山危机的管理具有直接和实际的应用。这项工作将以蒙特塞拉特Soufrière Hills火山(SHV)喷发为基础，结合另外两个活跃熔岩穹顶喷发--美国圣海伦斯火山和危地马拉圣地亚吉托火山--的初步比较研究。这种喷发发生的频率相对较高，可能具有极强的破坏性，可能会持续数年甚至数十年。因此，当这项研究中发现的关系被有效和成功地应用于其他地方的穹顶形成喷发时，真正的优点将会得到收获。这项工作的基本目标是严格量化与熔岩穹顶破坏和坍塌有关的活动方面，包括关于落石和火山碎屑流的时间和位置的信息，以及其他前兆活动的性质。该项目将解决需要进一步注意的三个问题：区分失效模式；确定结构控制；将坍塌视为大规模浪费的连续过程的一部分，而不是离散的独立事件。通过沿着这些主题进行研究，这项工作将验证现有模型并约束当前的一些限制。这项工作的结果将为开发统计驱动模型提供基础，以构建熔岩穹顶大规模流失的短期预测模型。这项研究的新颖性和影响取决于：比较不同监测数据集的创新技术，并生成将有助于火山界的穹顶活动的重要记录；了解持续生长和浪费过程，从而能够对物理机制进行评估，同时也为测试统计模型提供基础(通过收集大型数据集，提高统计模型的质量)；融合来自数字高程模型、热成像和气体羽状图的数据，制定一种真正综合的方法来了解穹顶不稳定性。

Lava domes are piles of viscous magma that, in essence, form bulbous plugs on top of volcanic vents. They grow slowly as partially solidified magma is squeezed up the volcanic conduit, and they can host high internal pressures as gases exsolving from the magma try to escape. Lava dome eruptions are notorious for they often suddenly transformation from being benignly effusive to violently explosive. Sudden removal of these plugs, either by vertically-driven explosions, caused once the internal gas pressure exceeds the tensile strength of rock, or sudden collapse and spontaneous disintegration as the piles grow and become unstable, can have devastating consequences. These collapse events spawn one of the major hazard in volcanology; devastating pyroclastic density currents, which move down the flanks of the volcano at speeds of up to 60 m/s. This project concerns the improved understanding and forecasting of lava dome collapses and has immediate and practical applications pertaining to the management of several on-going volcanic crisis. The work will be based on the Soufrière Hills volcano (SHV) eruption, Montserrat, combined with preliminary comparative studies from two other active lava dome eruptions, Mount St Helens, USA, and Santiaguito, Guatemala. Such eruptions occur with relative frequency, are potentially extremely destructive and can continue for years-to decades. The real merits therefore, will be reaped when relationships unearthed during this study are usefully and successfully applied to dome forming eruptions elsewhere.The fundamental objective of this work is to stringently quantify aspects of activity associated with lava dome failure and collapse including information on the timing and location of rockfalls and pyroclastic flows, as well as the nature of other precursory activity. The project will address three issues that require further attention: differentiating failure modes; identifying structural controls; and treating collapses as part of a continuous process of mass wasting rather than discrete independent events. By investigating along these themes, this work will validate existing models and constrain a number of current limitations. The results of this work will provide the basis from which statistically-driven models can be developed, in order to construct a short-term forecasting model of mass wasting at lava domes. The novelty and impact of this study hinges on: Innovative techniques for comparing disparate data sets of monitoring data, and the generation of an important record of dome activity that will be useful to the volcanological community; Understanding continuous growth and wasting processes allowing assessments to be made about physical mechanisms but also providing a basis for testing statistical models (the quality of which is enhanced by collection of large data sets); The fusion of data from digital elevation models, thermal images, and gas plume maps, developing a truly integrative approach to understanding dome instability.