New Caledonia consists of a cigar-shaped mainland (Grande Terre), the Isle of Pines, the Loyalty Group, and the small uninhabited dependencies of Walpole Island (125 hectares), the d'Entrecasteaux Reefs (64 hectares), and the more distant Chesterfield Islands (101 hectares). The d'Entrecasteaux Reefs consist of two separate lagoons centered on tiny Huon and Surprise Islands, with a deep strait 10 km wide between.
The territory's 18,575 square km are divided into three provinces: North Province (9,582 square km), South Province (7,012 square km), and Loyalty Islands Province (1,981 square km).
Grande Terre is part of the great fold in the earth's surface that runs from the central highlands of Papua New Guinea to the northern peninsula of New Zealand. The geology is complex, with metamorphic, sedimentary, and volcanic rock present.
Grande Terre is 400 km long and 50 km wide, the sixth-largest island in the Southwest Pacific (after New Guinea, the two islands of New Zealand, Tasmania, and New Britain).
Grande Terre is a fragment on the ancient continent of Gondwana of 60 million years ago. It's slowly sinking as the Indo-Australian Plate pushes under the Pacific Plate to the east; the winding, indented coastline is a result of this submergence. Ten km off both coasts is the second-longest barrier reef in the world, which marks how big the island once was. New Caledonia has a larger area of coral reefs than any other South Pacific territory.
The Loyalty Islands, on the other hand, are uplifted atolls with no rivers but many limestone caves. Maré, Tiga, Lifou, and Ouvéa form a chain 100 km east of Grande Terre. The Belep Islands and Isle of Pines are geological extensions of the main island. Walpole Island, 130 km east of the Isle of Pines, is also an uplifted limestone island three km long and 400 meters wide, with no protective reef around its 70-meter-high cliffs. Guano (fertilizer) was exploited here in 1910-36. The Huon Islands consist of four tiny coral islands 275 km northwest of Grande Terre, while the Chesterfields are 11 coral islets on a reef in the Coral Sea 550 km west-northwest of the main island. All of these dependencies are home to many species of seabirds.