ELECTRIC-POTENTIAL GRADIENT CHANGES DURING EXPLOSIVE ACTIVITY AT SAKURAJIMA VOLCANO, JAPAN
ELECTRIC-POTENTIAL GRADIENT CHANGES DURING EXPLOSIVE ACTIVITY AT SAKURAJIMA VOLCANO, JAPAN
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DOI：
10.1007/bf00569942
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发表时间：
1992-09-01
影响因子：
3.5
通讯作者：
GILBERT, JS
中科院分区：
文献类型：
--
作者：
LANE, SJ;GILBERT, JS
我们报告了在日本樱岛火山进行的电势梯度测量：(1)产生火山灰羽流的爆炸，(2)产生冷凝气体羽流的蒸汽爆炸，以及(3)火山灰和羽流引起的酸雨时期。在产生火山灰羽流的爆炸过程中，发生了连续的正偏差和负偏差。然而，在蒸汽爆炸期间没有发现背景偏转。在火山灰期间观察到负电位梯度，而在同一火山喷发引起的羽流引起的酸雨沉降期间观察到正电位梯度。这些结果表明，电偶极子分布在地幔柱内部，在火山气体丰富的顶部带正电荷，在地幔柱下部富火山灰的部分带负电荷。其他火山的电荷极性可能相反（Hatakeyama and Uchikawa, 1952）。我们认为电荷可能是在岩浆在喷口破碎的过程中由碎片发射（Donaldson et al. 1988）过程产生的，而不是由羽流内部的摩擦作用产生的。
We report electric potential gradient measurements carried out at Sakurajima volcano in Japan during: (1) explosions which generated ash plumes, (2) steam explosions which produced plumes of condensing gases, and (3) periods of ashfall and plume-induced acid rainfall. Sequential positive and negative deviations occurred during explosions which generated ash plumes. However, no deflections from background were found during steam explosions. During periods of ashfall negative electric potential gradients were observed, while positive potential gradients occurred during fallout of plume-induced acid rain from the same eruption. These results suggest that a dipole arrangement of charge develops within plumes such that positive charges dominate in the volcanic gas-rich top and negative charges in the following ash-rich part of the plume. The charge polarity may be reversed for other volcanoes (Hatakeyama and Uchikawa 1952). We suggest that charge is generated by fracto-emission (Donaldson et al. 1988) processes probably during magma fragmentation within the vent, rather than by frictional effects within the plume.