This study was conducted in a joint project on physical volcanology between Gadjah Mada University Yogyakarta, Indonesia and the Institute of Geophysics, University of Stuttgart, Federal Republic of Germany.
The question first considered by Wegener concerning the nature of the processes in the Earth bringing about continental drift and sea-floor spreading (or major displacements of the litosphere) in the last 100-200 myr, is probably the most important one in geoscience at the present time. The concept of plate tectonics has integrated the evidence for continental drift, sea-floor spreading and glo…