Deposits from dome-collapse and fountain-collapse pyroclastic flows at Soufriere Hills Volcano, Montserrat
Deposits from dome-collapse and fountain-collapse pyroclastic flows at Soufriere Hills Volcano, Montserrat
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DOI：
10.1144/gsl.mem.2002.021.01.11
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发表时间：
2002-01-01
期刊：
影响因子：
--
通讯作者：
Norton, GE
中科院分区：
文献类型：
--
作者：
Cole, PD;Calder, ES;Norton, GE
苏弗里耶尔火山的火山碎屑流是由熔岩穹顶塌陷和与火神爆炸相关的喷泉塌陷形成的。穹顶塌陷的主要事件持续数十分钟到几个小时，随后出现逐渐增大的流量和较长的跳动的升级模式。块灰流沉积体积范围为 < 0.1 至 25 x 10 6 m 3 ，径流为 1-7 km。这些流形成了粗粒块状和灰流沉积物，以及相关的细粒火山碎屑涌沉积物和灰烬沉积物。小流量通常形成叶状渠道化沉积物。无约束区域中的大量块体和灰烬流产生了边缘逐渐变细的片状沉积物。火山碎屑流的发展因地形和穹顶孔隙压力而异。火山碎屑涌动沉积物通常具有在当前锋面形成的缺乏细灰的下层和富含细灰的上层。块状和灰烬流具有侵蚀性，在早期沉积物中产生条纹和冲刷基岩表面，并形成数米深的通道。融入了大量偶然材料。喷泉塌陷形成的火山碎屑流沉积物为浮石质，具有狭窄的蜿蜒、叶状形态和发育良好的堤坝和口部。火山碎屑流进入大海的地方形成了两个沿海扇。它们向海的范围受到海底坡折的限制。
Pyroclastic flows were formed at Soufrière Hills Volcano by lava-dome collapse and by fountain collapse associated with Vulcanian explosions. Major episodes of dome collapse, lasting tens of minutes to a few hours, followed escalating patterns of progressively larger flows with longer runouts. Block-and-ash flow deposit volumes range from< 0.1 to 25 x 10 6 m 3 with runouts of 1-7 km. The flows formed coarse-grained block-and-ash flow deposits, with associated fine-grained pyroclastic surge deposits and ashfall deposits. Small flows commonly formed lobate channelized deposits. Large block-and-ash flows in unconfined areas produced sheet-like deposits with tapering margins. the development of pyroclastic surges was variable depending on topography and dome pore pressure. Pyroclastic surge deposits commonly had a lower layer poor in fine ash that was formed at the current front and an upper layer rich in fine ash. Block-and-ash flows were erosive, producing striated and scoured bedrock surfaces and forming channels, many metres deep, in earlier deposits. Abundant accidental material was incorporated. Pyroclastic flow deposits formed by fountain collapse were pumiceous, with narrow sinuous, lobate morphologies and well developed levees and snouts. Two coastal fans formed where pyroclastic flows entered the sea. Their seaward extent was limited by a submarine slope break.