Pyroclastic flows and surges generated by the 25 June 1997 dome collapse, Soufrière Hills Volcano, Montserrat
Pyroclastic flows and surges generated by the 25 June 1997 dome collapse, Soufrière Hills Volcano, Montserrat
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1997 年 6 月 25 日圆顶崩塌产生的火山碎屑流和涌流，苏弗里耶尔山火山，蒙特塞拉特
DOI：
10.1144/gsl.mem.2002.021.01.09
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
R. Watts
中科院分区：
文献类型：
--
作者：
S. Loughlin;E. Calder;A. Clarke;P. Cole;R. Luckett;M. Mangan;D. Pyle;R. Sparks;B. Voight;R. Watts
1997年6月25日，Soufrière Hills火山熔岩穹顶的一次不稳定的、倒退的部分坍塌持续了25分钟，产生了一股主要的脉动块状火山灰流、相关的火山碎屑涌流和由涌流产生的火山碎屑流，淹没了火山北侧和东北侧翼4平方公里的面积。估计有三个主脉冲涉及0.78、2.36和2.36×106m~3的碎石，并计算出相关块状和灰流脉冲锋面的平均速度分别为15ms-1、16.1ms-1和21.9ms-1。块和灰流脉冲1和2的沉积物部分填满了主排水渠道，因此第三个脉冲的物质在几个地方溢出，淹没了东部沿海平原上的村庄。主排水道中的弯曲和收缩，加上河道的沉积充填，有助于火山碎屑涌流从脉动的块状和灰流中剥离。最广泛的火山碎屑潮在早期脱离了第三次块状火山灰流脉冲，席卷了火山的北侧，然后上升了70米，然后消散。这股巨浪的快速沉积产生了高浓度的颗粒流(巨浪衍生的火山碎屑流)，向西排入一个预计不会有高风险的山谷。观察结果支持这样一种假设，即Soufrière Hills火山熔岩穹顶的内部受到了压力，随着更深、更高压力的穹顶部分被并入火山碎屑流中，火山碎屑浪涌的发育变得更加实质性。巨浪的发展有时是如此猛烈，以至于膨胀的云层在熔岩穹顶几十米范围内从块状和火山灰流动中分离出来。
Abstract On 25 June 1997, an unsteady, retrogressive, partial collapse of the lava dome at Soufrière Hills Volcano lasted 25 minutes and generated a major pulsatory block-and-ash flow, associated pyroclastic surges and a surge-derived pyroclastic flow that inundated an area of 4 km2 on the north and NE flanks of the volcano. Three main pulses are estimated to have involved 0.78, 2.36 and 2.36 x 106m3 of debris and the average velocities of the fronts of the related block-and-ash flow pulses were calculated to be 15 ms-1, 16.1 ms-1 and 21.9 ms-1 respectively. Deposits of block-and-ash flow pulses 1 and 2 partially filled the main drainage channel so that material of the third pulse spilled out of the channel at several places, inundating villages on the eastern coastal plain. Bends and constrictions in the main drainage channel, together with depositional filling of the channel, assisted detachment of pyroclastic surges from the pulsatory block-and-ash flow. The most extensive pyroclastic surge detached at an early stage from the third block-and-ash flow pulse, swept down the north flank of the volcano and then climbed 70 m in elevation before dissipating. Rapid sedimentation from this surge generated a high-concentration granular flow (surge-derived pyroclastic flow) that drained westwards into a valley not anticipated to be at high risk. Observations support the hypothesis that the interior of the Soufrière Hills Volcano lava dome was pressurized and that pyroclastic surge development became more substantial as deeper, more highly pressurized parts of the dome were incorporated into the pyroclastic flow. Surge development was at times so violent that expanded clouds detached from the block-and-ash flow within a few tens of metres of the lava dome.