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

Maars是被切割成喷发前景观的火山口，周围是低矮的喷出物或火山灰环。 它们是地球上最丰富的火山之一，最常出现在火山区，那里可能有数十或数百座火山。 玛珥火山的爆发对人口稠密地区和火山区重叠的地区构成了重大的危险。 由于它们涉及由热岩浆和地下水混合引起的剧烈爆炸，它们的喷发可能产生各种危险现象，包括冲击波、火山碎屑流、广泛分散的弹道块、火山灰降落和远距离移动的细灰羽流、大规模沉降和火山泥流。 Maars和它们下面的管道结构- diatremes -也可能具有经济重要性，特别是当喷发的岩浆是含钻石的金伯利岩时。 Diatremes通常抵抗侵蚀，并在挖掘景观，如科罗拉多高原，他们形成惊人的孤峰和尖塔（例如，新墨西哥州希普洛克和亚利桑那州纪念碑谷的部分地区）。 尽管它们具有危险性和经济重要性，但关于火山口下的地下过程以及这些过程与喷发现象的关系仍存在许多问题，该项目将年轻火山口的实地研究与旨在以米为尺度模拟火山形成过程的创新实验相结合。 实地研究将集中在两个年轻的玛珥，Dotsero（科罗拉多，年龄~4150岁）和Nilahue（智利南部，1955年喷发），原始的喷发后的几何形状可以很好地约束，火山灰沉积物主要是非硬结，因此可以进行成分和碎屑形状/纹理分析，次火山地层受到很好的约束，使我们能够将岩屑碎屑与其起源深度联系起来。 这些结果将与实验工作进行比较和解释，实验工作将使用人工分层“地质学”中的不同埋置爆炸物配置，从而可以确定陨石坑几何形状的特征，并详细分析不同深度喷出物的组成比例。 将用高速视频、地震仪和声学传感器监测爆炸，以限制动力学，实验后的挖掘将揭示产生的“diatremes”，以探索其结构和喷出物之间的关系。 实地和实验研究将极大地促进我们对火山爆发以及控制其危害和潜在经济资源的因素的理解。

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.