Tying textures of bread crust bombs to their transport regime and cooling history
Tying textures of bread crust bombs to their transport regime and cooling history
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DOI：
10.1016/j.jvolgeores.2014.02.005
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发表时间：
2014-03-15
影响因子：
2.9
通讯作者：
Rader, Erika
中科院分区：
文献类型：
--
作者：
Benage, Mary C.;Dufek, Josef;Rader, Erika
火山羽流和火山碎屑密度流 (PDC) 等爆炸性喷发事件的热演化反映在它们沉积的材料的结构中。在这里，我们评估如何将面包皮炸弹的外皮用作独特的温度计来检查镁铁质到中度爆炸性喷发。这些喷发可以在 PDC 中产生面包壳炸弹，或者以接近弹道轨迹的射弹形式产生。我们开发了一个集成模型来检查气泡生长、火山碎屑冷却以及 PDC 和浮力羽流射弹的动力学。我们研究了外皮发育与传输机制（PDC 和射弹）、传输特性（初始当前温度和电流密度）和火山碎屑特性（初始含水量和半径）的关系。模型表明：1）射弹火山碎屑的外皮一般比PDC火山碎屑的外皮更厚，且孔隙较少； 2）随着初始空气夹带导致初始当前温度降低，PDC火山碎屑上的外皮厚度逐渐增加； 3)果皮厚度随着水浓度的降低和碎屑半径的减小而增加。因此，模拟的火山碎屑的形态不仅取决于初始水浓度，还取决于冷却速率，而冷却速率由传输方式决定。 (C) 2014 Elsevier B.V. 保留所有权利。
The thermal evolution of explosive eruptive events such as volcanic plumes and pyroclastic density currents (PDCs) is reflected in the textures of the material they deposit. Here we evaluate how the rinds of breadcrust bombs can be used as a unique thermometer to examine mafic to intermediate explosive eruptions. These eruptions can produce breadcrust bombs in either PDCs or as projectiles following nearly ballistic trajectories. We develop an integrated model to examine bubble growth, pyroclast cooling, and dynamics of PDCs and projectiles from buoyant plumes. We examine rind development as a function of transport regime (PDC and projectile), transport properties (initial current temperature and current density), and pyroclast properties (initial water content and radius). The model reveals that: 1) rinds of projectile pyroclasts are in general thicker and less vesicular than those of PDC pyroclasts; 2) as the initial current temperature decreases due to initial air entrainment, the rinds on PDC pyroclasts progressively increase in thickness; and 3) rind thickness increases with decreasing water concentration and decreasing clast radius. Therefore, the modeled pyroclast's morphology is dependent not only on initial water concentration but also on the cooling rate, which is determined by the transport regime. (C) 2014 Elsevier B.V. All rights reserved.