Fragmentation of a porous viscoelastic material: Implications to magma fragmentation
Fragmentation of a porous viscoelastic material: Implications to magma fragmentation
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DOI：
10.1029/2001jb000591
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发表时间：
2002-10-01
影响因子：
3.9
通讯作者：
Sturtevant, B
中科院分区：
文献类型：
--
作者：
Ichihara, M;Rittel, D;Sturtevant, B
[1] 快速减压导致的泡状岩浆破碎是最可能引发爆炸性喷发的触发因素之一。在这种现象中，减压率和岩浆的粘弹性性质被认为是关键因素。为了清楚地了解这两个因素的影响，进行了受控碎裂实验。这些实验具有三个优点。首先，样本由具有受控孔隙率和几何形状的粘弹性材料制成。其次，直接监控分片过程。最后，控制减压的幅度和速率。在不同时间尺度的相同多孔材料中都观察到脆性破碎和延性膨胀。样本的各种机械响应（弹性、流动和破碎）与在样本底部测量的压力分布相关。当减压在关键时间内超过临界值时，就会发生碎片。根据放松的物理机制讨论了两个相关的时间尺度。第一个是测量的玻璃化转变时间。第二个是粘性气泡膨胀开始的估计时间尺度。观察到的现象与自然岩浆破碎有一些相似之处。因此，目前的结果被认为是构建岩浆破碎模型的有用一步。
[1] Fragmentation of vesicular magma by rapid decompression is one of the most likely triggers for explosive eruptions. In this phenomenon the decompression rate and the viscoelastic nature of magma are considered to be key factors. In order to obtain a clear idea on the effects of these two factors, controlled fragmentation experiments have been conducted. These experiments have three advantages. First, the specimen is made of a viscoelastic material with controlled porosity and geometry. Second, the fragmentation process is directly monitored. Finally, both the magnitude and rate of decompression are controlled. Brittle fragmentation and ductile expansion were both observed in the same porous material at different timescales. The various mechanical responses of the specimen (elastic, flow, and fragmentation) were correlated with the pressure profile measured at the base of the specimen. Fragmentation was noted to occur when the decompression exceeded a critical value within a critical time. Two relevant timescales are discussed in terms of physical mechanisms of relaxation. The first is the measured glass transition time. The second is the estimated timescale for the onset of viscous bubble expansion. The observed phenomena bear several similarities with natural magma fragmentation. It is thus considered that the present results are a useful step toward constructing a model for magma fragmentation.