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

MAARs是切割成喷发前景观的火山口，周围环绕着低调的喷出物或火山灰环。它们是地球上最丰富的火山之一，最常见的出现在火山田，那里可能有数十或数百个单独的火山。在人口稠密地区与火山田重叠的地方，MAAR喷发构成了重大危险。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、火山灰落下和远距离传播的细火山灰羽流、大规模下沉和火山泥石流。MAARS及其下伏的管道结构--岩浆--也可能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。Diatreme通常抵抗侵蚀，在出土的景观中，如科罗拉多高原，它们形成了醒目的突起和尖顶(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)。尽管它们具有危害性和经济重要性，但许多问题仍然存在于岩浆之下的地下过程以及这些过程与喷发现象的关系。该项目结合了对年轻岩浆的实地研究和创新实验，旨在以米级的规模模拟形成火山的过程。野外研究将集中于两个年轻的Maar，Dotsero(科罗拉多州，年龄约4150岁)和Nilahue(智利南部，1955年喷发)，在那里原始的喷发后几何结构可以得到很好的约束，Tephra矿床基本上没有硬化，因此适合进行成分和碎屑形状/结构分析，而次火山地层学受到很好的限制，使我们能够将岩屑与它们的成因深度联系起来。这些结果将与在人工分层“地质学”中使用不同形状的埋藏炸药的实验工作进行比较和解释，以便描述陨石坑的几何形状，并根据从不同深度得出的比例详细分析喷射物的成分。爆炸将用高速视频、地震仪和声学传感器进行监测，以限制动力学，实验后的挖掘将揭示为了探索它们的结构和喷射物之间的关系而产生的“方向”。总之，实地和实验研究将极大地促进我们对玛雅火山喷发及其控制其危害和潜在经济资源的因素的了解。

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.