Western Pacific Geosynclinal Belt

a mobile region of the earth’s crust in the western Pacific and its littoral region, extending from the Aleutian Islands to New Zealand.

The belt forms part of the Pacific Geosynclinal Belt. The division of the latter into the Eastern Pacific (Cordillera) Geosynclinal Belt and the Western Pacific Geosynclinal Belt is not accepted by all researchers. The so-called andesite line serves as the eastern border of the Western Pacific Geosynclinal Zone; its western area includes Chukotka, Kamchatka, the Sikhote-Alin’ Mountains, Japan, southeast China, the Philippines, the Celebes Islands, New Guinea, eastern Australia, and Tasmania.

Plicate regions of the Mesozoic period (in the west) and the Cenozoic period (in the east) predominate in the Western Pacific Geosynclinal Belt. In China and Australia, however, the plicate regions are older. A wide belt of inner seas framed by island arcs forms the eastern part of the zone. Deep-water oceanic trenches stretch out from the outer side of the island arcs. Chains of active and recently extinct volcanoes extend across Kamchatka and along the island arcs. Many researchers consider this belt, characterized by high seismicity as well, to be a modern geosynclinal region in an active period of development. An oceanic type of earth’s crust or an intermediary type (between continental and oceanic) is characteristic of the inner seas.