Geography of New Caledonia

An expandable bathymetric and topographic map of New Caledonia and Vanuatu, formerly the New Hebrides. Click to enlarge.

New Caledonia is made up of a main island, the Grande Terre, and several smaller islands, the Belep archipelago to the north of the Grande Terre, the Loyalty Islands to the east of the Grande Terre, the (Isle of Pines) to the south of the Grande Terre, the Chesterfield Islands and Bellona Reefs further to the west. Each of these four island groups has a different geological origin:

• The New Caledonia archipelago, which includes Grande Terre, Belep, and the Île des Pins was born as a series of folds of the earth's mantle between the Permian period (251–299 mya) and the Paleogene and Neogene periods (1.5–66 mya). This mantle obduction created large areas of peridotite and a bedrock rich in nickel.
• The Loyalty Islands, a hundred kilometers to the east, are coral and limestone islands built on top of ancient collapsed volcanoes originating due to subduction at the Vanuatu trench.
• The Chesterfield Islands, 550 kilometres (340 miles) to the northwest, are reef outcroppings of the oceanic plateau.
• The Matthew and Hunter Islands, at 450 and 520 kilometres (280 and 320 miles) east, respectively, are volcanic islands that form the southern end of the arc of the New Hebrides.

The Grande Terre is by far the largest of the islands, and the only mountainous island. It has an area of 16,372 square kilometres (6,321 square miles), and is elongated northwest–southeast, 350 kilometres (220 miles) in length and 50 to 70 kilometres (31 to 43 miles) wide. A mountain range runs the length of the island, with five peaks over 1,500 meters (4,900 feet). The highest point is Mont Panié at 1,628 meters (5,341 feet) elevation. The total area of New Caledonia is 19,060 km² (7,360 sq mi), 18,575 km² (7,172 sq mi) of those being land.

A territorial dispute exists with regard to the uninhabited Matthew and Hunter Islands, which are claimed by both France (as part of New Caledonia) and Vanuatu.

Topography of Zealandia. New Caledonia is the slender island in the top left quadrant of the image at 11 o'clock from New Zealand. The ridges running north-northeast and southwest from New Zealand are not part of the continent.[8]

The New Caledonian archipelago is a microcontinental island chain which originated as a fragment of Zealandia, a nearly submerged continent or microcontinent which was part of the southern supercontinent of Gondwana during the time of the dinosaurs. The Grande Terre group of New Caledonia, with Mont Panié at 1,628 meters (5,341 feet) as its highest point, is the most elevated part of the Norfolk Ridge, a long and mostly underwater arm of the continent.[9] While they were still one landmass, Zealandia and Australia combined broke away from Antarctica between 85 and 130 million years ago. Australia and Zealandia split apart 60–85 million years ago.[10] Although biologists consider it contrary to the evidence of surviving Gondwanan lineages, geologists consider the logical possibility that Zealandia may have been completely submerged about 23 million years ago.[11][12] While a continent like Australia consists of a large body of land surrounded by a fringe of continental shelf, Zealandia consists almost entirely of continental shelf, with the vast majority, some 93%, submerged beneath the Pacific Ocean.[9] This viewpoint is not universal. Bernard Pelletier argues that Grande Terre was completely submerged for millions of years, and hence the origin of the flora may not be local in nature, but due to long distance-dispersal.[13]

Zealandia is 3,500,000 km² (1,351,358 sq mi) in area, larger than Greenland or India, and almost half the size of Australia. It is unusually slender, stretching from New Caledonia in the north to beyond New Zealand's subantarctic islands in the south (from latitude 19° south to 56° south,[10] analogous to ranging from Haiti to Hudson Bay or from Sudan to Sweden in the Northern Hemisphere). New Zealand is the greatest part of Zealandia above sea level, followed by New Caledonia.[10]

Given its continental origin as a fragment of Zealandia, unlike many of the islands of the Pacific such as the Hawaiian chain, New Caledonia is not of geographically recent volcanic provenance. Its separation from Australia at the end of the Cretaceous (65 mya) and from New Zealand in the mid-Miocene has led to a long period of evolution in near complete isolation. New Caledonia's natural heritage significantly comprises species whose ancestors were ancient and primitive flora and fauna present on New Caledonia when it broke away from Gondwana millions of years ago, not only species but entire genera and even families are unique to the island, and survive nowhere else.

Since the age of the dinosaurs, as the island moved north due to the effects of continental drift, some geologists assert that it may have been fully submerged at various intervals. Botanists, however, argue that there must have been some areas that remained above sea level, serving as refugia for the descendants of the original flora that inhabited the island when it broke away from Gondwana. The isolation of New Caledonia was not absolute, however. New species came to New Caledonia while species of Gondwanan origin were able to penetrate further eastward into the Pacific Island region.

Upi Bay on the southern Isle of Pines

The climate of New Caledonia is tropical, modified by southeasterly trade winds. It is hot and humid. Natural hazards are posed in New Caledonia by cyclones, which occur most frequently between November and March. While rainfall in the neighboring Vanuatu islands averages two meters annually, from the north of New Caledonia to the south the rain decreases to a little over 1,000 mm (39 in). The mean annual temperature drops over the same interval from 27.5 to 24.3 °C (81.5 to 75.7 °F), and seasonality becomes more pronounced. The capital, Nouméa, located on a peninsula on the southwestern coast of the island normally has a dry season which increases in intensity from August until mid-December, ending suddenly with the coming of rain in January. The northeastern coast of the island receives the most rain, with 2,400 mm (94 in) having been recorded near sea level in Pouébo.[14]

The terrain of Grande Terre consists of coastal plains, with mountains in the interior. The lowest point is the Pacific Ocean, with an elevation of 0 m, and the highest is Mont Panie, with an elevation of 1,628 m (5,341 ft).

The Diahot River is the longest river of New Caledonia, flowing for some 60 miles (97 kilometres).[22] It has a catchment area of 620 square kilometres and opens north-westward into the Baie d'Harcourt, flowing towards the northern point of the island along the western escarpment of the Mount Panie.[22][23]

In 1993, 12% of New Caledonian land was used for permanent pasture, with 39% occupied by forests and woodland. In 1991, 160 km² (62 sq mi) of the land was irrigated. A current environmental issue is erosion caused by mining exploitation and forest fires.

The enigmatic kagu, an endemic New Caledonian bird with no close relatives. See pictures of the erected crest and of wing patterns exposed during defensive posturing at the San Diego Zoo website.

Amborella trichopoda, the world's most primitive flowering plant

Correlophus ciliatus, the not-yet-extinct crested gecko of southern Grande Terre isle

Meiolania platyceps fossil

Given its geographical isolation since the end of the Cretaceous, New Caledonia is a refugium, in effect a biological "Noah's Ark", an island home to both unique living plants and animals and also to its own special fossil endowment. Birds such as the crested and almost flightless kagu (French, cagou) Rhynochetos jubatus, whose closest relative may be the distantly related sunbittern of South America, and plants such as Amborella trichopoda, the only known member of the most basal living branch of flowering plants, make this island a treasure trove and a critical concern for biologists and conservationists. The island was home to horned fossil turtles (Meiolania mackayi) and terrestrial fossil crocodiles (Mekosuchus inexpectatus) which became extinct shortly after human arrival. There are no native amphibians, with geckos holding many of their niches. The crested gecko (Correlophus ciliatus), thought to have gone extinct, was rediscovered in 1994.[24] At 14 inches, Leach's giant gecko (Rhacodactylus leachianus), the world's largest[25] and a predator of smaller lizards is another native. The only native mammals are four species of bat including the endemic New Caledonia flying fox.[26]

New Caledonia is home to 13 of the 19 extant species of evergreens in the genus Araucaria. The island has been called "a kind of 'Jurassic Park'"[27] because of the archaic characteristics of its highly endemic vegetation. In addition to the basal angiosperm plant genus Amborella, for example, the island is home to more gymnosperm species than any other tropic landmass, with 43 of its 44 conifer species being unique to the island, which is also home to the world's only known parasitic gymnosperm, the rootless conifer Parasitaxus usta.[28]

Given their prehistoric appearance, the dry forests of western New Caledonia were chosen as the location for filming the first episode of the BBC miniseries Walking with Dinosaurs, which was set in the Arizona of the late Triassic.

After a formation discovered in Oman in the 1970s, New Caledonia has the planet's largest known outcrop of ultrabasic rock, derived not from the crust, but from an upthrust fold of the more deeply underlying mantle of the earth.[29] These mineral-rich rocks are a source of nickel, chromium, iron, cobalt, manganese, silver, gold, lead and copper. The toxicity of the mineral-rich soil has helped preserve the endemic vegetation, which has long been adapted to it, from competition from would-be colonizers which find it unsuitable.[30]

• d'Entrecasteaux Ridge
• List of islands of New Caledonia

Other microcontinental islands:

• Madagascar
• Seychelles
• Socotra

 This article incorporates public domain material from The World Factbook. CIA.

• Croixdusud.info a site in both English and French including information on the geography, geology, and biodiversity of the area