Bubble-quantitative volcanology

该项目的目的是建立从浮石或碎屑的囊状结构定量火山喷发的方法。这个目标还没有实现，但我们已经得到了以下几个重要的事实，这些事实将对这个项目的进一步发展有价值。(1)利用板状囊泡估算管道内应变速率的尝试：以托雅火山浮石流沉积为例，发现囊泡宽高比与大小的关系对估算火山管道内应变速率具有重要作用。(2) 1986年伊豆大岛火山B火山口Plinian喷发岩屑的结构分析：研究发现，岩屑囊泡度与陆块微岩数量密度呈负相关，喷发早期和后期以微岩贫型（A型）为主，喷发中期以微岩富型为主。如果脱气作用下有效液相线的升高控制了微岩的结晶，这一事实表明，在喷发过程中，岩浆上升速率由慢、快、再到慢变化。(3)酵母发酵烘焙面包实验：从自由膨胀发酵与玻璃管发酵的实验结果对比来看，一维膨胀增强了气泡的聚结和伸长。这一结果已在托雅火山的首次研究中得到考虑。这三项研究证实了该项目的基本思想，即泡状结构可以为火山喷发的定量提供重要信息。

The aim of this project has been to establish the methodology for the quantification of volcanic eruptions from the vesicular texture of pumices or scoriae. This aim has not bee achieved yet but we have get several important facts that will be valuable to the further development of this project as follows. (1) Attempt to estimate the strain rate in the conduit using tabular vesicles : In the case study of pumice flow deposit in Toya volcano, we found that the relationship between aspect ratio and size of vesicles plays an important role to estimate the strain rate in the volcanic conduit. (2) The textural analysis of scoria from the B crater Plinian eruption of 1986 Izu-oshima volcano : In this research, we found that the vesicularity and the number density of groundmass microlites negatively correlate and that in the early and final stages of the eruption the microlite-poor type (A type) is dominated whereas in the middle stage the microlite-rich type is dominated. If the elevation of the effective liquidus due to the degassing controls the microlite crystallization, this fact suggests that the magma ascent rate in conduit changes from a slow, through fast and to slow rates again during the eruption. (3) The experiment of bread baking using yeast fermentation : From the comparison of experimental results between the fermentation under free expansion and that in glass tubes, the 1 dimensional expansion enhances the bubble coalescence and elongation. This result has been taken into account in the first study concerning Toya volcano. These three studies confirm the underlying idea of this project that the vesicular texture can provide the important information for the quantification of volcanic eruption.