Experimental Pyroclastic Density Currents

人们对火山碎屑流知之甚少，它是膨胀的气体和热灰的危险混合物，可以以超过100公里/秒的速度移动数十公里。火山碎屑流的观察是危险的，而且很少与研究人员的时间一致。因此，这个项目将开始一个多学科的研究，以调查火山碎屑流是如何工作的。在实验室浇注600℃可产生火山碎屑密度电流。在被水浸湿的倾斜表面上撒灰。初步实验成功地产生了具有许多自然火山碎屑流特征的流。流动的气流有三个部分；一个富含沉积物的基底雪崩，一个覆盖的火山灰云涌流和一个对流的火山灰云。实验流动的环境条件很容易单独控制，对流动的影响也很明显。主要关注的是影响火山碎屑流流动性的因素，因为跳动在危害评估中具有明显的重要性。这样的研究结果可能会改善火山碎屑流危害的评估，这是火山学家的一项重大社会责任。

Pyroclastic flows are poorly understood, hazardous mixtures of expanding gas and hot ash that can move tens of kilometers at velocities in excess of 100 km/sec. Pyroclastic flows are dangerous to observe and rarely coincide with researchers'timing. This project, therefore, will begin a multi-disciplinary study to investigate how pyroclastic flows work. Pyroclastic density currents can be produced in the laboratory by pouring 600oC. ash down an inclined surface that is moistened with water. Preliminary experiments successfully produce flows with many of the features of natural pyroclastic flows. A moving flow has three parts; a sediment-rich basal avalanche, an overriding ash cloud surge and a convecting ash cloud. The environmental conditions of experimental flows can be easily controlled individually and the effects on the flow noted. Of principle concern are the factors that affect the mobility of pyroclastic flows because of the obvious importance of runout in hazard assesment. The results of such a study are likely to improve the assesment of hazards due to pyroclastic flows, which is a serious societal responsibility for volcanologists.