A geographic designation that includes thousands of mainly small coral and volcanic islands scattered across the Pacific Ocean from Palau in the west to Easter Island in the east. Island archipelagos off the coast of the Asian mainland, such as Japan, Philippines, and Indonesia, are not included even though they are located within the Pacific Basin. The large island constituting the mainland of Papua New Guinea and Irian Jaya is also excluded, along with the continent of Australia and the islands that make up Aotearoa or New Zealand. The latter, together with the Asian Pacific archipelagos, contain much larger landmasses, with a greater diversity of resources and ecosystems, than the oceanic islands, commonly labelled Melanesia, Micronesia, and Polynesia. See also Australia; New Zealand; Oceanic islands.
The great majority of these islands are between 4 and 4000 mi2 (10 and 10,000 km2) in land surface area. The three largest islands include the main island of New Caledonia (6220 mi2 or 16,100 km2), Viti Levu (4053 mi2 or 10,497 km2) in Fiji, and Hawaii (4031 mi2 or 10,440 km2) the big island in the Hawaiian chain. When the 80-mi (200-km) Exclusive Economic Zones are included in the calculation of surface area, some Pacific island states have very large territories. These land and sea domains, far more than the small, fragmented land areas per se, capture the essence of the island world that has meaning for Pacific peoples. See also East Indies.
Oceanic islands are often classified on the basis of the nature of their surface lithologies. A distinction is commonly made between the larger continental islands of the western Pacific, the volcanic basalt island chains and clusters of the eastern Pacific, and the scattered coral limestone atolls and reef islands of the central and northern Pacific.
It has been suggested that a more useful distinction can be drawn between plate boundary islands and intraplate islands. The former are associated with movements along the boundaries of the great tectonic plates that make up the Earth's surface. Islands of the plate boundary type form along the convergent, divergent, or tranverse plate boundaries, and they characterize most of the larger island groups in the western Pacific. These islands are often volcanically and tectonically active and form part of the Pacific so-called Ring of Fire, which extends from Antarctica in a sweeping arc through New Zealand, Vanuatu, Bougainville, and the Philippines to Japan.
The intraplate islands comprise the linear groups and clusters of islands that are thought to be associated with volcanism, either at a fixed point or along a linear fissure. Volcanic island chains such as the Hawaii, Marquesas, and Tuamotu groups are classic examples. Others, which have their volcanic origins covered by great thickness of coral, include the atoll territories of Kiribati, Tuvalu, and the Marshall Islands. Another type of intraplate island is isolated Easter Island, possibly a detached piece of a mid-ocean ridge. The various types of small islands in the Pacific are all linked geologically to much larger structures that lie below the surface of the sea. These structures contain the answers to some puzzles about island origins and locations, especially when considered in terms of the plate tectonic theory of crustal evolution. See also Marine geology; Mid-Oceanic Ridge; Plate tectonics; Seamount and guyot; Volcano.
The climate of most islands in the Pacific is dominated by two main forces: ocean circulation and atmospheric circulation. Oceanic island climates are fundamentally distinct from those of continents and islands close to continents, because of the small size of the island relative to the vastness of the ocean surrounding it. Because of oceanic influences, the climates of most small, tropical Pacific islands are characterized by little variation through the year compared with climates in continental areas.
The major natural hazards in the Pacific are associated either with seasonal climatic variability (especially cyclones and droughts) or with volcanic and tectonic activity. See also Climate history.
