噴火のダイナミックス : 噴火タイプおよび噴出物・堆積物の性質の観点から(＜特集＞火山学50年間の発展と将来)

抄録

About thirty years ago Walker (1973) proposed a diagram to classify explosive volcanic eruptions producing pyroclastic falls on the basis of extensive field data. This diagram has provided us a framework to quantitatively describe explosive eruptions in terms of the characteristics of fall deposits and has also motivated us to develop theoretical models of explosive eruptions. Some of the universal relationships observed in this diagram, such as the positive correlation between the degree of tephra dispersal and the degree of magma fragmentation from sub-plinian to ultra-plinian eruptions may be useful as criteria to verify existing theoretical models. Recent progress in theoretical models of eruption columns, conduit flow, bubble nucleation and growth and magma fragmentation is reviewed from the viewpoint how these models are verified by field data of pyroclastic fall deposits.