THE WEST PACIFIC GEODYNAMIC MODEL

Between the Asian and Australian continents on the western side and the general subduction of the Central Pacific on the eastern side, the west Pacific presents two types of subduction: towards the continents and towards the ocean. As a consequence, at the present day there are two main types of marginal seas-the Japan Sea and the South China Sea-and, in the geological past, two types of orogenesis-the Japanese and the Taiwanese types. These are the models of the two main orogenic belts, respectively the Circum-Pacific and Tethyan. For a long period of the past, the Alps and the Mediterranean Sea were the tectonic model of reference. However with the increase in geological studies, oceanographic research, geophysical surveying, the west Pacific gradually became an alternative model which grew more useful with each passing day. The present-day trench-island arc-marginal sea system appears to be a good model for the first stages of orogenic belts, whereas the mountains of the east Eurasian margins provide an example of the completion of formation of such belts. The coexistence of different stages of mountain building is the main reason for the increasing interest shown by earth scientists in the west Pacific. © 1990.