a major tectonic division of the earth's crust, comprising India and the Australian continent and adjacent suboceanic basins (the Tasman, South Australian, Mid-Indian, Cocos, and Australian basins); separated from the Eurasian Plate by the Java Trench, from the Pacific Plate by the Tonga-Kermadec Trench, and from the African Plate by a series of mid-ocean ridges (the Carlsberg, Mid-Indian, and Southeast Indian ridges)