Short Time Physics During Fragmentation of Basaltic and Intermediate Magma

岩浆由连续变形向脆性破坏的转变是各类爆发性火山喷发的共同特征。但是，是什么决定了岩浆体积中的应力分布呢？持续变形和碎裂需要多少能量？为了解决这些问题，在维尔茨堡大学建立了一个实验装置，在喷发温度下驱动熔体塞从静止状态通过连续变形状态进入脆性破坏。这一过程由高速压力和力传感器以及高速视频系统记录。可以测量临界变形率以及特定的碎裂能量，并将这种能量应用于自然火山环境，以评估火山爆发所涉及的总能量。进一步的问题产生于这些实验：什么是岩浆的弹性，粘性，几何约束和泡状/孔隙度的影响？因此，上述实验必须在几个方面加以扩展。它将被称为斯塔尔（“短时间尺度加速高负荷”）实验，并将针对选定的具有众所周知特性的天然火山物质以及当前感兴趣的物质（例如来自有据可查的2010年埃亚菲亚德拉冰盖爆发的物质）进行测试。最后的结果可以缩放到自然火山的情况下，并作为大规模的实验和数值模拟的输入参数。我们希望找到这样的问题的答案：“产生火山灰需要多少能源？"

The transition from continuous deformation to brittle failure of magma is common to all types of explosive volcanic eruptions. But what determines how stress is distributed in the magma volume? How much energy is necessary for continuous deformation and for fragmentation? To address such questions an experimental apparatus was built at the Universität Würzburg driving a melt plug at eruption temperatures from rest through the continuous deformation regime into brittle failure. This process was recorded by high-speed pressure- and force sensors, and a high-speed video system. It was possible to measure the critical deformation rate as well as the specific fragmentation energy, and to apply this energy to natural volcanic settings in order to assess the overall energies involved in explosive volcanic eruptions. Further questions arise from these experiments: What is the influence of magma elasticity, -viscosity, geometrical confinement and vesicularity/porosity? Therefore the above described experiment must be extended in several points. It is intended to be called STAHL ("Short Timescale Accelerated High Load") experiment, and will be tested against selected natural volcanic materials with well known properties, as well as materials of current interest (e.g. from the well documented Eyjafjallajökull 2010 eruptions). Finally the results can be scaled to natural volcanic scenarios and serve as input parameters for large scale experiments and numerical simulations. We hope to find answers to questions like: "How much energy needs to be payed to produce volcanic ash?"