The Dynamics of Short-Duration, Unsteady Volcanic Eruptions

世界上550多座历史上活跃的火山中，约有30座得到了充分监测，尽管它们对正在侵蚀的人类人口构成威胁。更好地预测火山喷发的时间和规模对于减少对这些脆弱人群的风险至关重要。为此，科学家们正试图确定爆炸性喷发动力学中目前尚未识别的模式，并随后建立可靠的预测模型。大的、持续的(普林尼安)喷发的计算机模型，如芒特山喷发。1980年5月18日圣海伦斯或1991年6月12日菲律宾皮纳图博火山喷发，形成了我们目前理解的基础。然而，尽管脉动或不稳定的源属性被认为对喷发行为有重大影响，但通过对密度和速度等关键源属性进行时间平均，这样的模型必然会得到简化。为了应对这种明显的脱节，这项研究的目的是在不稳定的源条件和爆炸性喷发动力学之间建立牢固的关系。这项研究将侧重于小型、短暂、高度不稳定的(火山)喷发，这些喷发比普林尼亚喷发发生得更频繁，因此是加强对喷发动力学的一般了解和改进模型的宝贵和可获得的数据来源。火山喷发产生的最致命的现象之一是火山喷发柱的坍塌和由此产生的火山碎屑流(热气、块状物质和火山灰的雪崩)。火山喷发带来的复杂性和危险性促使实验室进行调查，目的是根据推动喷发的不稳定力量，确定稳定的、上升的喷发柱和不稳定的、产生火山碎屑流的柱之间的过渡。特别令人感兴趣的是，初始浮力和动量力的变化如何影响这些流动的灰分和速度分布的变化。该团队还将测试现有喷发数学模型在捕捉简单实验室实验行为方面的有效性。同时，他们将评估相同的模型是否有效地代表了真实的火山喷发。该项目的最终目标是从理论上理解由脉冲、不稳定来源产生的各种流动，包括大规模爆炸性火山喷发、工业爆炸、污染羽流、森林火灾和许多其他现象。

Approximately 30 of the more than 550 historically active volcanoes in the world are adequately monitored despite the threats they pose to encroaching human populations. Better predictions of volcanic eruption timing and scale are critical for reducing risk to these vulnerable populations. To that end, scientists are attempting to identify currently unrecognized patterns in explosive eruption dynamics and subsequently build reliable predictive models. Computer models of large, sustained (Plinian) eruptions, like the eruption of Mt. St. Helens on May 18, 1980, or the June 12, 1991 eruption of Pinatubo volcano in the Philippines, form the basis of our current understanding. However, despite the fact that pulsating or unsteady source properties are thought to have significant impact on eruption behavior, such models are necessarily simplified by time-averaging key source properties such as density and velocity. In response to this apparent disconnect, this research aims to establish robust relationships between unsteady source conditions and explosive eruption dynamics. The study will focus on small, short-lived, highly unsteady (vulcanian) eruptions, which occur much more frequently than Plinian eruptions, and are thus a valuable and accessible source of data for enhancing general understanding of eruption dynamics and improving models. Collapsing eruption columns and resulting pyroclastic flows (avalanches of hot gas, blocks and ash) are one of the deadliest phenomena produced in explosive volcanic eruptions. The complexity and danger presented by volcanic eruptions motivates the laboratory investigations that will take place with the aim to define the transition between stable, rising eruption columns and unstable, pyroclastic-flow-producing columns in terms of the unsteady forces driving the eruption. Of particular interest is how variations in the initial buoyancy and momentum forces influence changes in the ash and velocity distribution of these flows. The team will also test the effectiveness of existing mathematical models of eruptions in capturing the behavior of simple laboratory experiments. Simultaneously, they will assess whether the same models are valid representations of real volcanic eruptions. The ultimate goal of the project is to establish theoretical understanding of a wide-range of flows generated by impulsive, unsteady sources, including large-scale explosive volcanic eruptions, industrial explosions, contaminant plumes, forest fires and many other phenomena.