Degassing Dynamics that Lead to Repeated Lava Dome Growth and Collapse at Persistently Active Stratovolcanoes

导致持续活跃的成层火山熔岩穹丘反复生长和塌陷的排气动力学

• 批准号: 1358886
• 负责人: Kimberly Genareau
• 金额: $ 11.65万
• 依托单位: University of Alabama Tuscaloosa
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1358886&HistoricalAwards=false
• 关键词: Degassing; Dynamics; Lead; Repeated; Lava

The October 2010 eruption of Mt. Merapi, one of Indonesia?s most active volcanoes, demonstrates the devastation and sudden loss of human life that can result from even moderate to small eruptions of active stratovolcanic systems throughout the world. The ability to observe current activity on Merapi, and the existence of preserved erupted sequences resulting from long-lived activity, allow for a detailed examination of volatile degassing dynamics during lava dome growth and major dome collapse events. It also provides an opportunity to formulate a general model of how such systems evolve over time. Because lava dome growth and collapse is a dominant mechanism for the production of dangerous and unpredictable volcanic phenomena (e.g., pyroclastic density currents, ash fall) that have devastating effects on both local and regional populations, understanding the physical parameters that trigger dome collapse events and influence the generation of pyroclastic hazards is paramount to improving the hazard mitigation strategies at this persistently active stratovolcano. In exploring the causes of major dome collapse events at andesitic stratovolcanoes, this project seeks evidence for geochemical and textural signals for these impending events in erupted products, with the objective of determining how the dynamics of volatile degassing during lava effusion contributes to particular characteristics of resulting pyroclastic density currents and ash fall hazards. Existing samples collected from Merapi will be targeted by a focused range of analyses in order to constrain similarities or differences in particular characteristics between single eruptive events and temporal variations over the long-term course of eruptive activity, including: 1. Grain size distributions of fall and flow units and ash grain morphologies within the most efficiently fragmented portion of the tephra.2. Microlite number density and microlite morphology within lava samples, plagioclase phenocryst rim compositions, rim textures, and amphibole reaction rim thicknesses. 3) Lava vesicularity, vesicle morphology, bubble size distributions, and development of permeable networks for gas escape during dome growth. 4) Behavior of volatile elements (H2O, CO2, Li) in minerals and melts during magma ascent and dome effusion. By comparing several dome-producing events over time within a single stratovolcanic system, this study seeks to quantify the rheological parameters leading up to major dome collapse events, attempting to explain why these collapse events occur, why they occur on variable time scales, and how the behavior of volatile elements and the degassing of these elements will influence the resulting characteristics of pyroclastic hazards. Quantifying the physical parameters within volcanic conduits and understanding how these parameters vary over time to cause major dome collapse events will allow researchers to more accurately model (and ultimately, forecast) volcanic behavior. This will lead to improved hazard assessment strategies for not only Merapi, which represents a significant volcanic hazard for the nation of Indonesia, but for the other 100 active stratovolcanic centers throughout the world that display similar behavior.

2010年10月，印度尼西亚最活跃的火山之一默拉皮山（Merapi）爆发表明，人类生命的破坏和突然丧失，甚至可能是由于全世界活跃的层状电载体系统的中度到小型喷发所致。观察当前活动对梅拉皮的活性的能力，以及由于长寿活动而导致的爆发序列的存在，可以详细检查熔岩圆顶生长和主要圆顶倒塌事件期间挥发性脱气动力学的详细检查。 它还提供了一个机会，可以制定一个通用模型，以了解此类系统如何随着时间的流逝而发展。因为熔岩圆顶的生长和崩溃是生产危险和不可预测的火山现象（例如，火山碎屑密度电流，灰落）对当地和区域人口具有毁灭性影响的主要机制，了解触发圆顶事件的物理参数造成了巨大的影响，并影响了Proloclastic Heabards的产生，这是策略危险的危险。在探索安第斯山脉Stratovolcanoes的主要圆顶崩溃事件的原因时，该项目为这些即将发生的产品中这些即将发生的事件的地球化学和纹理信号寻求证据，目的是确定熔岩积液过程中挥发性脱发动力学的动力学如何有助于产生的pyroclastic密度密度水流和Ash Ash Ash Fall affer。 从梅拉皮收集的现有样品将由集中的分析范围作为目标，以限制单个喷发事件与时间变化之间特定特征的相似性或差异。熔岩样品，斜长石晶晶缘成分，边缘纹理和闪石反应边缘厚度内的微层数密度和微矿形态。 3）熔岩囊泡，囊泡形态，气泡尺寸分布以及圆顶生长过程中气体逸出的可渗透网络的发展。 4）在岩浆上升和圆顶积液过程中，矿物质和熔体中挥发性元素（H2O，CO2，LI）的行为。 By comparing several dome-producing events over time within a single stratovolcanic system, this study seeks to quantify the rheological parameters leading up to major dome collapse events, attempting to explain why these collapse events occur, why they occur on variable time scales, and how the behavior of volatile elements and the degassing of these elements will influence the resulting characteristics of pyroclastic hazards. 量化火山导管中的物理参数，并了解这些参数如何随着时间而变化以引起主要的圆顶塌陷事件，这将使研究人员更准确地建模（并最终，预测）火山行为。 这将导致改善对梅拉皮的危害评估策略，不仅是对印度尼西亚国家的重要火山危害，而且还代表了世界上其他100个活跃的Stratovolcanic中心，全世界都表现出相似的行为。