The author’s academic research started in 1954 as a Research Associate in the laboratory of physical volcanology of the Earthquake Research Institute, University of Tokyo. In the beginning in 1957, I published a paper titled “On the relation between the eruption of Sakurajima Volcano and the crustal movements in its neighborhood” (Mogi, 1957, in Japanese), in which I proposed a model to explain the crustal deformation caused by a volcanic eruption. However, there was no response to the paper in Japan. In the next year, I wrote a similar, but more extended paper (Mogi, 1958) in English. Immediately a number of volcanologists in the world had interest and they applied this model to similar problems at many volcanoes, which is continuing to the present. Ryan et al (1983) wrote “Mechanical models of the internal structure of active volcanic systems dates from the work of Mogi (1958)” at the beginning of the historical review in their paper. This model is quite simple and applicable to many volcanoes, and it is often called the Mogi model.