Geological and petrological study on phreatomagmatic explosions of the Miyakejima eruption in 2000

2000年三宅岛喷发的岩浆爆发地质和岩石学研究

基本信息

批准号：
16340166
负责人：
NAKADA Setsuya
金额：
$ 8.38万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

The mechanisms of phreatomagmatic explosions that occurred during the eruption at Miyakejima in 2000 were investigated based on geological inspection of the products together with the geophysical monitoring data and video footage. Comparative study was also carried out for the eruptions in Anatahan (Northern Mariana Islands) during 2003-2005 and in the Akademy Nauk lake (Kamchatka) in 1996. In Miyakejima, tephra of every explosion events were identified in many places and the depositional times were determined using stratigraphical makers. Eruption volume of tephra of each explosion event gave the precise eruption rates. The fragmentation extents of magma and whole products of each event were estimated by grain analysis. Component analysis gave the proportion of contribution of magma to each explosion event. These data are very valuable parameters to model the explosions of hydrovolcanic eruptions, which nobody could have presented by this study.There is positive correlation between th … More e magma eruption rate and the height of ashy eruption column, and negative correlation between the extent of fragmentation and magma eruption rate. The latter means the highest extent of fragmentation in non-magmatic explosions. Such the high fragmentation may result from (1) repeated fragmentation of coarse grains within the crater, which failed to rise due to the lack of thermal energy and (2) the effect of supercritical water that breaks silicate into pieces immediately. The lines of evidence showing the most effective energy conversion from heat to fragmentation at the mgama-water ration of 0.3, proposed by Wahletz was not confirmed in the present eruption.Large contribution of groundwater into the Miyakejima eruption in 2000 is also verfied by the appearance of erupted products and the isotopic ratios of materials attached to the products. Further investigation including textural comparison of products from the Anatahan and Akadamy Nauk is needed to clarify the circumstance of phreatomagmatic explosions. Less

根据对产品的地质检查以及地球物理监测数据和视频录像，研究了2000年在Miyakejima爆发期间发生的phreatomagmagmatic爆炸机制。 1996年，在2003年至2005年的Anatahan（北玛丽安娜群岛）和Akademy Nauk Lake（Kamchatka）的爆发也进行了比较研究。在Miyakejima，使用层间培养家确定了在许多地方，在许多地方确定了每个爆炸事件的Tephra。每个爆炸事件的Tephra的喷发量给出了精确的喷发率。通过晶粒分析估算岩浆和整个产品的碎片化量。组件分析给出了岩浆对每个爆炸事件的贡献的比例。这些数据是建模水力降解爆发的非常有价值的参数，这项研究没有任何介绍。后者是指非魔术爆炸中碎片的最高程度。这样的高碎片可能是由于（1）火山口内的粗粒重复碎片引起的，由于缺乏热能，由于缺乏热能而无法上升，并且（2）超临界水的效果将硅胶立即分解成碎片。瓦赫尔茨（Wahletz）提出的最有效的能量转化为0.3的麦加马 - 水评估的能量转化，在演示喷发中尚未确认。在2000年，地下水对宫基jima爆发的贡献也通过产品的外观和材料的同位素比的外观得到证实。进一步的研究包括需要对来自Anatahan和Akadamy Nauk的产品进行质地比较，以阐明phreatomagmatic爆炸的情况。较少的