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Bubble-quantitative volcanology

气泡定量火山学

基本信息

批准号：
10440127
负责人：
TORAMARU Atsushi
金额：
$ 6.98万
依托单位：
kanazawa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

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.

该项目的目的是建立从浮石或火山渣的泡状结构量化火山喷发的方法。这个目标还没有实现，但我们已经得到了几个重要的事实，这将是有价值的进一步发展这个项目如下。(1)尝试使用板状泡估计管道中的应变率：在洞屋火山的浮石流存款的案例研究中，我们发现，之间的关系的纵横比和大小的泡在火山管道中的应变率估计起着重要的作用。(2)1986年伊豆大岛火山普林尼期喷发B火山口火山渣的结构分析：研究发现，火山岩基质微粒的泡孔度与微粒数密度呈负相关，在喷发的早期和晚期以贫微粒型（A型）为主，中期以富微粒型为主。如果有效液相线的升高，由于脱气控制微晶结晶，这一事实表明，岩浆上升速度在导管从一个缓慢的变化，通过快速和缓慢的速度再次在喷发期间。(3)酵母发酵烘焙面包实验：通过比较自由膨胀发酵和玻璃管发酵实验结果，发现一维膨胀促进了气泡的聚结和伸长。这一结果已在有关托雅火山的第一次研究中得到考虑。这三项研究证实了本项目的基本思想，即泡状结构可以为火山喷发的量化提供重要信息。