Volcanic Conduit Processes and Strombolian Eruption Cycles

火山导管过程和斯特龙堡火山喷发周期我们在这个项目中的目的是了解火山背后的驱动力，这些火山显示出持续的斯特龙堡火山活动。这种活动的特点是反复发生轻度爆炸性事件。像意大利的斯特隆博利火山（Stromboli Volcano）那样，这种重复的爆炸活动要维持几百到几千年，火山必须有稳定的岩浆和气体供应。然而，这种供应是由离散岩浆群的反复上升还是由连续的岩浆流产生的，目前还没有确定。1999年5月，我们在斯特隆博利进行的初步测量表明，浅层系统的岩浆供应确实可能在几分钟到一小时的长时间内发生变化（也就是说，它可能是批状的）。这些供应的变化可能反过来驱动已观察到的爆炸活动形式和频率的变化。这使我们提出了一个可行的假设，即新鲜的、富含气体的岩浆确实以离散脉冲的形式从深处升起，引起脱气水平的波动，因此在它们到达时发生了爆炸性活动。我们目前的项目建立在这些初步测量的基础上，增加了新的地球物理仪器，并对火山产物进行了更详细的检查。特别是，我们将使用热和次声测量，加上对喷发熔岩弹的结构的研究，来检查斯特隆博利的爆炸活动，并推断管道内岩浆水平的变化。在斯特隆波利爆炸之间发生的持续脱气过程中获得的热数据将用于表征增强气体逸出的时期。最后，我们将利用炸弹中的囊泡（气泡）和晶体大小分布来限制新到达的岩浆批和长期驻留的岩浆在浅层系统中的混合程度。

Volcanic Conduit Processes and Strombolian Eruption CyclesEAR-0207734PIs: Harris & HoughtonOur aim in this project is to understand the driving forces behind volcanoes that display persistent, strombolian activity. Such activity is characterized by repeated, mildly explosive events. For such repetitive explosive activity to be maintained over hundreds-to-thousands of years, as it has been at Stromboli Volcano (Italy), a volcano must be fed by a stable supply of magma and gas. It has not yet been determined, however, whether this supply occurs by the repeated rise of discrete magma batches or by a continuous stream.Initial measurements by us at Stromboli during May 1999 indicated that the magma supply to the shallow system may indeed be variable over minutes-to-hour long periods (i.e. it may be batch-like). These supply variations may in turn drive observed variations in the style and frequency of explosive activity. This has led us to develop a working hypothesis that fresh, gas-rich magma batches do rise from depth as discrete pulses, causing fluctuating levels of degassing and hence explosive activity upon their arrival. Our current project builds on those initial measurements by adding new geophysical instrumentation together with more detailed examination of volcanic products. In particular, we will use thermal and infrasound measurements, plus studies of the textures of the erupted lava bombs to examine explosive activity at Stromboli and infer variations in magma level within the conduit. Thermal data acquired during the persistent degassing that occurs between strombolian explosions will be used to characterize periods of enhanced gas escape. Finally, we will use vesicle (gas bubble) and crystal size distributions in the bombs to constrain the extent of mixing between newly arrived magma batches and long-resident magma within the shallow system.