Relationships Between Subsurface Processes, Eruptive Products and Surface Morphology of Maar-diatreme Volcanoes

Maar-diatreme 火山地下过程、喷发产物与地表形态之间的关系

• 批准号: 1420455
• 负责人: Greg Valentine
• 金额: $ 27.52万
• 依托单位: SUNY at Buffalo
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1420455&HistoricalAwards=false
• 关键词: Relationships; Between; Subsurface; Processes; Eruptive

Maars are volcanic craters cut into a pre-eruptive landscape, surrounded by low-profile ejecta or tephra rings. They are among the most abundant volcanoes on Earth, and occur most commonly in volcanic fields where there may be tens or hundreds of individual volcanoes. Maar eruptions present a significant hazard where populated regions overlap with volcanic fields. Because they involve violent explosions caused by mixing of hot magma and groundwater, their eruptions can produce a full gamut of dangerous phenomena including blast waves, pyroclastic flows, widely dispersed ballistic blocks, ash fall and far-travelled fine ash plumes, large-scale subsidence, and volcanic mudflows. Maars and their underlying plumbing structures - diatremes - can also be of economic importance, especially when the erupted magma is diamond-bearing kimberlite. Diatremes commonly resist erosion, and in exhumed landscapes such as the Colorado Plateau they form striking buttes and pinnacles (e.g., Shiprock, New Mexico, and parts of Monument Valley, Arizona). Despite their hazards and economic importance, many questions remain about the subsurface processes beneath maar-diatremes and the relationships of those processes to eruptive phenomena.This project combines field studies at young maar-diatremes with innovative experiments that are intended to mimic, at the scale of meters, the processes that form the volcanoes. Field studies will focus on two young maars, Dotsero (Colorado, age ~4150 yrs) and Nilahue (southern Chile, erupted 1955) where original post-eruptive geometry can be well constrained, the tephra deposits are largely non-indurated and therefore amenable to component and clast shape/texture analysis, and sub-volcanic stratigraphy is well constrained, allowing us to link lithic clasts to their depths of origin. These results will be compared with and interpreted in light of experimental work that will use different configurations of buried explosives in artificial layered "geologies," allowing for characterization of crater geometry and detailed analysis of the composition of ejecta in terms of proportions derived from different depths. Explosions will be monitored with high-speed video, seismometers, and acoustic sensors in order to constrain dynamics, and post-experimental excavation will reveal the "diatremes" that are produced in order to explore the relationship between their structure and ejecta. Together, the field and experimental studies will greatly advance our understanding of maar-diatreme eruptions and the factors that control their hazards and potential economic resources.

玛尔斯火山口是在喷发前形成的火山口，周围环绕着低调的喷射物或火山灰环。 它们是地球上最丰富的火山之一，最常见于可能有数十或数百座火山的火山田。 玛珥火山喷发在人口稠密地区与火山区重叠的地方造成重大危险。 由于它们涉及热岩浆和地下水混合引起的猛烈爆炸，因此它们的喷发会产生一系列危险现象，包括冲击波、火山碎屑流、广泛分散的弹道块、火山灰落下和远行的细小火山灰羽流、大规模沉降和火山泥流。 马尔斯及其下面的管道结构（diatremes）也具有重要的经济意义，特别是当喷发的岩浆是含钻石的金伯利岩时。 Diatremes 通常能抵抗侵蚀，在科罗拉多高原等挖掘出的景观中，它们形成引人注目的山丘和尖峰（例如新墨西哥州的希普罗克和亚利桑那州纪念碑谷的部分地区）。 尽管存在危害和经济重要性，但关于 maar-diatremes 下的地下过程以及这些过程与喷发现象的关系仍然存在许多问题。该项目将年轻的 maar-diatremes 的现场研究与旨在大规模模拟的创新实验结合起来米，形成火山的过程。 实地研究将集中于两个年轻的火山，Dotsero（科罗拉多州，年龄约 4150 年）和 Nilahue（智利南部，1955 年喷发），那里原始喷发后的几何形状可以得到很好的限制，火山灰沉积物大部分是非硬结的，因此适合于成分和碎屑形状/纹理分析，并且火山下地层受到很好的约束，使我们能够将岩屑联系起来碎屑到达它们的起源深处。 这些结果将与实验工作进行比较和解释，这些实验工作将在人工层状“地质”中使用埋藏炸药的不同配置，从而能够表征弹坑的几何形状，并根据来自不同深度的比例对喷射物的成分进行详细分析。 爆炸将通过高速视频、地震仪和声学传感器进行监测，以限制动力学，实验后挖掘将揭示产生的“diatremes”，以探索其结构与喷射物之间的关系。 总之，现场研究和实验研究将极大地增进我们对玛尔迪亚特雷姆火山喷发以及控制其危害和潜在经济资源的因素的理解。