Ashmore and Cartier Islands (ăsh`mōr, cär'tē-ā`), unhabited tropical islands, 2 sq mi (5 sq km), E Indian Ocean, a dependency of Australia located 190 mi (300 km) NW of N Western Australia. Ashmore Reef is comprised of three coral islets (West, Middle, and East) enclosed by a coral reef. Cartier Island, 33 mi (53 km) to the southeast, is sandy and also surrounded by a reef. The island and the islets are each about 0.5 mi (0.8 km) wide. The group came under Australian authority in 1931. A national nature reserve, Ashmore Reef abounds with bird and ocean life. Cartier Island, once a bombing range, is now a marine reserve.