Reliefs
Grande Terre is crossed in its center, from north to south, by a 400 km long mountain chain. If the two big summits, Mount Panié in the north and Mount Humboldt in the south, reach 1,628 and 1,618 m, the average altitude of the chain rarely exceeds 1,000 m. The impact of these mountains on the climate and geography of both coasts is significant. You can see this for yourself by driving the transverse roads from the West to the East coast. New Caledonia is very varied in terms of relief and offers multiple possibilities. From the sea to the great plains and the mountain tops, the archipelago is a top destination. The reef barrier, 10 to 65 km from the coast of Grande Terre, reveals a magnificent lagoon dotted with islets and submerged coral patches, the kingdom of sailing, windsurfing and scuba diving enthusiasts. On the Loyalty Islands, the limestone plateau of these ancient raised coral atolls never exceeds 100 m. The lagoon, if it exists in Ouvéa, is on the other hand filled in on Maré and Lifou.
Main regions
There isNouméa, and then there is the rest of New Caledonia! This vast commune (5,000 hectares) is the nerve center of New Caledonia, in even greater proportions than Paris in relation to the province: together with the outlying communes, it concentrates more than half the population of the territory! Most of the political and economic institutions are grouped in the capital, as well as many infrastructures. Nouméa also sometimes resembles a city on the French Riviera. Outside Nouméa, the country is very different, in the bush and in the islands.
The west coast "Côte sous-le-vent" is much less watered than the east coast. As a comparison, it falls on average 1.06 m of water in Noumea for 1.70 m in Houaïlou. Grasslands and niaouli savannah occupy a large area between the shores of the sea and the foothills of the chain. Economically, livestock farming remains one of the main activities of the West Coast. In this littoral zone, mangroves proliferate on a salty and marshy soil, which shelters in particular mangrove trees which compose mangroves with a unique ecosystem. The central range has a cooler and wetter climate and dense vegetation. You will meet tribes settled in the upper valleys, accessible by tracks. Their locations are marked along the road with small signs. The rainforests are located in the massif near Bourail and in the Koghis massif in Dumbéa. Four main administrative centers follow one another once you leave Nouméa: La Foa, Bourail, Koné and Koumac. These are small towns that drain all the surrounding activity of the stations (farms) and tribes.
The magnificent East coast or "Windward coast", exposed to the trade winds, has the characteristics of a tropical zone: heat, abundant rain, dense and luxuriant vegetation. It is here that the tribes are the most numerous in the territory: 80% of the population is Melanesian. It is also a large mining area: Thio and Kouaoua in the south remain major nickel mining centers. In terms of infrastructure, the construction of new roads and the maintenance of existing roads remain expensive and some regions are sometimes difficult to access, especially the access to the tribes of the chain. The pronounced relief and torrential rains do not simplify the task. The mountainous chain, contrary to the west coast, almost plunges into the sea and overhangs the road from the top of its peaks. North of Hienghène, the rainforest covers the Mount Panié massif, as in the Thio region with the Willow forest or the Haute Combue. This primary forest testifies to the power of a nature not domesticated by man, which favors the isolated valleys and the sides of the mountains. Kaoris, beeches, anteaters and bagnans remind us what the environment owes to the trees.
The extreme North. Residents will tell you about the north of the territory, from Koumac onwards, as if it were a separate state, the most remote region of the Rock. It is the completion of the central chain that dies on a jagged coast, enigmatic and dotted with islands and islets, which are spaced out to the distant horizon for the Belep. The narrow, winding and hilly road, which leads to the northern end of the archipelago, stretches its long ribbon of asphalt in the middle of a dazzling landscape where the red of the earth competes with the green of the shrubs and niaoulis (trees), trace of the many fires that ravaged the place. Then at the end, the track will take you to Boat Pass, after Poingam. Be careful when driving on the trail and make sure your rental car can take you there. This end of the world, planted there in the heart of the Southern Hemisphere, with its forested mountains, savannah and coconut tree lined bays, seems to be shared between Australia, New Zealand and sometimes even Canada... Passing from east to west, you cross the mining maquis with its dry and airy vegetation. The "ironwood" tree symbolizes well the area. Extremely hard, it is used for the construction of the huts and more particularly for the posts of support.
The South. Provincial Road No. 3 (PR 3) crosses the region bounded by the steep and winding pass of Mouirange (255 m), the lake of the Yaté dam and the village of Yaté on one side and Unia on the other. Lovers of wide open spaces will find their account there. The largest mining massif in New Caledonia, the South immediately marks the traveler, generally hypnotized by the vivacity of a red earth rich in iron oxide. The tribes are concentrated between Unia, Yaté and Goro, on the South-East coast, and in Plum on the South-West coast. This vast area is very sparsely populated... It is nevertheless the occasion to rub shoulders with the laterite, which sticks to the road and impregnates everything. The hydrometallurgical plant of Goro, Vale, processes the low grade laterite and extracts nickel and cobalt. In the middle of these virgin and arid territories, seven botanical reserves have been established. On the ocean side, the warm waters of Prony Bay are home to humpback whales between July and September. Ouen Island and the Isle of Pines mark the extremities of this great South.
The outlying islands. The archipelago, in addition to the main island (Grande Terre), also includes smaller islands. The Loyalty Islands, located about 100 km east of Grande Terre and 30 minutes by plane from Nouméa, include Ouvéa, Lifou, Tiga and Maré. As an indication, Lifou alone is larger than Martinique, but it is only populated by 15,000 inhabitants! The Isle of Pines, south of the rock, covers 150 km². The tiny archipelago of Bélep, 50 km from the northern tip of the territory, includes the islands of Art, Pott and Dau Ac spread over 70 km². Some of the more remote islets are even uninhabited, such as Huon and Surprise, in the heart of the Entrecasteaux reefs, 300 km northwest of Grande Terre. To the west, the Chesterfield Islands and the Bellone Reefs still offer the opportunity to forget civilization. To the east, near Ouvéa, Beautemps, Beaupré and Astrolabe almost naturally stimulate the imagination. The isolated islets of Walpale, Matthews and Hunter, in the southeast are claimed by Vanuatu.
Lagoon and coral reef
In this field, superlatives are useless: the figures speak for themselves. 24,000 km² of lagoon surrounded by 1,600 km of reef! These figures give the measure of the exceptional maritime environment enjoyed by New Caledonia. In 2008, UNESCO placed part of the Caledonian reef on the World Heritage list: 2,000 species of fish with unique colors and shapes inhabit these prodigious waters, whose temperature ranges from 21 to 28°C. The growth of corals, shellfish and fish is therefore assured. Even humpback whales, which visit the South lagoon and Lifou between July and September, meet near the coast of the territory. Divers can explore caves covered with sponges and bryozoans. The terrestrial relief extends under the sea with a continental shelf submerged up to 60 km from the coastal strip. In the shallowest areas, coral reefs have been built up over a period of 10,000 years. The annual growth of corals varies from 1 to 10 cm depending on the species. Most coral reefs are fringing. Once developed on the island base, they grow until they reach the water surface (depending on the height of the tides). Specific zones distinguish the reef space. The back reef depression is located between the coast and the emerging part of the reef (the platier). You can swim in it. The reef bed, for its part, is covered with a few centimeters of water or several meters, depending on the tides. The waves break on its outer edge. It is the ideal area for palm-walking. You will be fascinated by the succession of basins and coral spats. The water can be murky (from 5 to 20 meters of visibility), due to the presence of sand or water from rivers flowing into the lagoon. The coral reef delimits the end of the lagoon with an inner slope - often superb to explore - and an outer slope facing the open sea, where the turquoise blue turns into marine blue. The outer, plunging zone is the growth zone of the reef. The profile of the slopes is subject to significant hydrodynamics: the breakers break as soon as the reef is exposed to the wind. The fringing reefs are in fact constructions fixed to the shore, while the barrier reefs are separated from the islet by the lagoon.
Hydrography
The rivers are formed in the central chain and therefore mostly flow from this transverse axis. The watersheds are very short and in case of heavy rains, the rivers swell to excess. The waterfalls, often splendid, will resound along your route in the heart of the steep valleys of the east coast. Towards the west coast, the rivers in the plain form long meanders that meander, then towards the estuaries, widen and turn into mangroves with salt meadows, swamps, mangroves are then omnipresent. Good to know: none of these rivers is navigable and cannot be travelled upstream beyond 6 or 7 km. Many Caledonians practice kayaking there. Be careful, however, when swimming in these areas, as they are hunting and breeding grounds for bulldog sharks. The government has installed artificial dams, in particular on the Dumbéa River, to supply Nouméa with water. In Yaté, the dam provides hydroelectric power. Isolated tribes are supplied with electricity by small hydroelectric power stations installed on secondary rivers. During heavy rainfall, floods are violent and can devastate everything in their path. The crossing of rivers by fords and riffles is then difficult, if not impossible, and the small roads and tracks quickly become impassable. Ask for information before you leave and check the weather forecast when you use less frequented routes. In the bush, during rainy periods, avoid drinking water that is usually drinkable. Its color, ochre, indicates quite clearly its content.
Tides
They are semi-diurnal. Two high tides and two low tides occur daily. The tide directory is on sale in the nautical stores of Noumea. It contains information about Grande Terre and the Loyalty Islands.
Currents
They are violent near the passes, these holes dug in the reef barrier, where the aquatic exchanges between the lagoon and the ocean take place. But the passes are very far from the coast. The tide can indeed oppose the wind and agitate the waves, which then break at the entrance or exit of the pass. The rise in sea level submerges the reef belt and gives rise to very strong currents from the ocean to the lagoon: the channel currents. This turbulence, due to the frontal encounter between the current and the swell, or the wind, also has a name: the tidal bore. As a general rule, when the current is incoming, the water is clearer, but the fauna less dense. When the current is outgoing, from the lagoon to the ocean, the water is murkier, full of nutrients, and attracts many fish. In the absence of swell or opposing currents, the tidal bore is practically non-existent. The emptying and filling of the channel is not always easy to anticipate. They depend on wind variations, river flow and daily meteorology. Good to know: fish of all sizes are present.
Geology
300 million years ago, New Caledonia was part of the huge Indo-Australian plate called Gondwana, which included Antarctica, South America, Africa, India and Australia. It will only break away 160 million years later at the same time as New Zealand. Then 100 million years passed before this new block split. New Zealand then headed south, while New Caledonia moved northeast. It is estimated that New Caledonia will meet the neighbouring Vanuatu within 2 million years. The Loyalty Islands should then sink under the plate supporting Vanuatu. This area of the Pacific is very sensitive to seismic effects, this is especially true for Vanuatu.
Richness of the Caledonian soil
New Caledonia's subsoil abounds in mineral wealth, but generally not industrially exploitable apart from nickel and cobalt. Lithographic limestone is mined at Nouville (Noumea) and jasper at Païta (west coast). The Prony area (south) abounds in zoïsite and the Ouen Island quarry in jade. The rivers of Thio (east) and Koumac (north) contain dunite. Through subtle geological processes, the minerals contain up to 6% nickel, whose saturation gives the stone a beautiful green color. Discovered by Jules Garnier, garnierite (from which nickel is extracted) is a good illustration of this geological phenomenon. Born in Saint-Etienne in 1839 and a graduate of the Ecole des Mines, Jules Garnier was sent on a mission to New Caledonia where he became fascinated with the country... and with nickel, of course, and discovered a process for extracting it. After registering a patent for the industrial exploitation of this precious mineral, he participated in the creation of what would become the Société Le Nickel-SLN, which still exists today. Nickel mining and metallurgy are now the mainstay of New Caledonia's industrial activity. Most of this extraction comes from the processing of laterites and mountain ores. Nickel is produced by the surface alteration of rocks due to the action of the tropical climate. It then accumulates in layers. The territory concentrates 20 to 40% of the world's known nickel resources and has become the fourth largest producer in the world. Three plants, the oldest at Doniambo at the entrance to Nouméa, the second at Goro in the south and the third at VKP (Voh-Koné-Pouembout) produce nearly 130,000 tonnes of nickel per year. While iron shot and chromium (red) were previously considered waste, the collapse of nickel prices in 1998, due to the fall in the yen (Asian crisis) and the introduction of Russian nickel on the market, changed the situation. The omnipresence of nickel on Grande Terre inevitably attracts the eye of the traveler. Huge trucks loaded with red earth rush along the roads and docks. From the road that runs along the west coast, miners are busy scraping the mountainside. The open-pit mining of nickel, which extends into the heart of the mountain, gives a red hue to the massifs, a striking contrast with the green of the forests. The Kopeto mountain, between Népoui and Pouembout (west coast), is a perfect example. The rise in nickel prices in 2018, linked to the strong demand for cobalt for electric car batteries, is giving a boost to this key sector.
