Simulating maar–diatreme volcanic systems in bench-scale experiments

Maar–diatreme eruptions are incompletely understood, and explanations for the processes involved in them have been debated
for decades. This study extends bench-scale analogue experiments previously conducted on maar–diatreme systems and attempts
to scale the results up to both field-scale experimentation and natural volcanic systems to produce a reconstructive toolkit
for maar volcanoes. These experimental runs produced via multiple mechanisms complex deposits that match many features seen
in natural maar–diatreme deposits. The runs include deeper single blasts, series of descending discrete blasts, and series
of ascending blasts. Debris-jet inception and diatreme formation are indicated by this study to involve multiple types of
granular fountains within diatreme deposits produced under varying initial conditions. It is not possible to infer the energies
of single blasts in multiple-blast series from the final deposits. The depositional record of blast sequences can be ascertained
from the proportion of fallback sedimentation versus maar ejecta rim material, the final crater size and the degree of overturning
or slumping of accessory strata. Quantitatively, deeper blasts involve a roughly equal partitioning of energy into crater
excavation energy versus mass movement of juvenile material, whereas shallower blasts expend a much greater proportion of
energy in crater excavation.

马亚-地穹喷发现象尚不完全为人所解，涉及其中的过程亦历经数十载之争论。本研究在先前对马亚-地穹系统进行的实验室尺度模拟实验基础上，力图将实验结果扩展至现场尺度实验以及自然火山系统，旨在为马亚火山构建一套重建工具。通过多种机制产生的实验运行，形成了与自然马亚-地穹沉积物中众多特征相吻合的复杂沉积物。实验运行包括更深层次的单一爆破、一系列递减的离散爆破以及一系列递增的爆破。本研究指出，碎片流的形成和地穹的形成涉及多种类型的颗粒喷泉，这些喷泉产生于不同的初始条件下的地穹沉积物中。从最终沉积物中无法推断出多爆破系列中单一爆破的能量。通过爆破序列的沉积记录，可以确定 fallback 沉积物与马亚火山弹边缘材料的比例、最终火山口的大小以及附属地层翻转或滑坡的程度。从定量角度看，深层爆破的能量大致均等地分配于火山口挖掘能量和年轻物质的移动，而浅层爆破则将大量能量消耗于火山口挖掘。