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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Ash aggregation during the 11 February 2010 partial dome collapse of the Soufriere Hills Volcano, Montserrat
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Ash aggregation during the 11 February 2010 partial dome collapse of the Soufriere Hills Volcano, Montserrat

机译：蒙特塞拉特Soufriere Hills火山在2010年2月11日部分穹顶塌陷期间的灰烬聚集

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On 11 February 2010, Soufriere Hills Volcano, Montserrat, underwent a partial dome collapse (similar to 50 x 10(6) m(3)) and a short-lived Vulcanian explosion towards the end. Three main pyroclastic units were identified N and NE of the volcano: dome-collapse pyroclastic density current (PDC) deposits, fountain-collapse PDC deposits formed by the Vulcanian explosion, and tephra-fallout deposits associated with elutriation from the dome-collapse and fountain-collapse PDCs (i.e. co-PDC fallout deposit). The fallout associated with the Vulcanian explosion was mostly dispersed E and SE by high altitude winds. All units N and NE of the volcano contain variable amounts and types of particle aggregates, although the co-PDC fallout deposit is associated with the largest abundance (i.e. up to 24 wt%). The size of aggregates found in the co-PDC fallout deposit increases with distance from the volcano and proximity to the sea, reaching a maximum diameter of 12 mm about 500 m from the coast. The internal grain size of all aggregates have nearly identical distributions (with Md phi approximate to 4-5), with particles in the size categories > 3 phi (i.e. < 250 mu m) being distributed in similar proportions within the aggregates but in different proportions within distinct internal layers. In fact, most aggregates are characterized by a coarse grained central core occupying the main part of the aggregate, coated by a thin layer of finer ash (single-layer aggregates), while others have one or two additional layers accreted over the core (multiple-layer aggregates). Calculated aggregate porosity and settling velocity vary between 03 and 0.5 and 11-21 ms(-1), respectively. The aggregate size shows a clear correlation with both the core size and the size of the largest particles found in the core. The large abundance of aggregates in the co-PDC fallout deposits suggests that the buoyant plumes elutriated above PDCs represent an optimal environment for the formation (particle collision) and development (aggregate layering) of particle aggregates. However, specific conditions are required, including i) a large availability of water (in this case provided by the steam plumes associated with the entrance of PDCs into the ocean), ii) presence of plume regions with different grain-size features (i.e. both median size and sorting) that allows for the development of multiple layers, iii) strong turbulence that permits both particle collision and the transition of the aggregates through different plume regions, iv) presence of hot regions (e.g. PDCs) that promote aggregate preservation (in this case also facilitated by the presence of sea salt). (c) 2017 Elsevier B.V. All rights reserved.
机译：2010年2月11日，蒙特塞拉特的Soufriere Hills Volcano经历了部分穹顶塌陷（类似于50 x 10（6）m（3）），并在生命周期结束时发生了短暂的Vulcanian爆炸。火山的N和NE被确定为三个主要的火山碎屑单元：圆顶塌陷的火山碎屑密度流（PDC）沉积物，由Vulcanian爆炸形成的喷泉塌陷的PDC沉积物以及与圆顶塌陷和喷泉的淘洗相关的Tephra沉降沉积物-崩溃PDC（即，共同PDC余尘存款）。 Vulcanian爆炸带来的尘埃落差主要是由高空风分散的E和SE。火山的所有N和NE单元都包含数量和类型不同的颗粒聚集体，尽管co-PDC沉降沉积物的丰度最大（即最高24 wt％）。在共PDC沉降沉积物中发现的聚集体的大小随与火山的距离和与海洋的距离的增加而增加，最大直径为12 mm，距海岸约500 m。所有骨料的内部晶粒尺寸具有几乎相同的分布（Md phi约为4-5），尺寸类别> 3 phi（即<250μm）的颗粒以相似的比例分布在骨料中在不同的内部层中。实际上，大多数骨料的特征是粗粒状中心核占据骨料的主要部分，并被一层薄薄的细灰覆盖（单层骨料），而其他骨料则在核上增添了一层或两层（多层层聚合）。计算出的总孔隙率和沉降速度分别在03和0.5以及11-21 ms（-1）之间变化。聚集体的大小与核的大小以及在核中发现的最大颗粒的大小都显示出明显的相关性。 co-PDC沉降沉积物中大量的聚集体表明，PDC上方淘析的浮羽代表了颗粒聚集体形成（颗粒碰撞）和发展（聚集体分层）的最佳环境。但是，需要特定的条件，包括：i）大量的水（在这种情况下，是与PDC进入海洋相关的蒸汽羽流所提供的），ii）存在具有不同粒度特征的羽流区域（即两者中值尺寸和分类），允许多层发展; iii）强湍流，允许颗粒碰撞以及聚集体通过不同羽状区域的过渡; iv）存在促进聚集体保存的高温区域（例如PDC）这种情况也因海盐的存在而变得容易。 （c）2017 Elsevier B.V.保留所有权利。

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