Tuamotu Archipelago
The Tuamotu Archipelago (Archipel des Tuamotu) is the Earth's largest cluster of atolls, forming a major
portion of France's overseas department of French Polynesia. In total there are 73 true atolls, four low coral islands,
one raised coral island and one large island-barrier-reef complex; the archipelago has a total land area of
885 km². From Mataiva in the northwest to Temoe in
the far southeast the archipelago forms a series of loose chains stretching in a northwesterly to southeasterly
direction across some 2,000 km of the South Pacific.
The Tuamotu atolls exhibit a wide variety of forms, ranging from tiny circular-shaped atolls such as those of Niau and Anuanurunga to the large elongated structures of atolls such as Mururoa and Rangiroa. Some of the atolls of the Tuamotu Archipelago are amongst the largest and most impressive of atolls found anywhere on earth — with Rangiroa and Fakarava being the largest of the Tuamotu atolls. Many of the atolls here display the archetypal atoll morphology: delicate, almost perfectly circular rings of coral reefs sitting atop submerged mountains of volcanic origins. Others have more irregular shapes. One of the atolls, Makatea, has been geologically uplifted to form a cliff-lined coral island ('makatea'). While former atolls such as Nukutuvake and Tepoto Nord have lost their lagoons due to sedimentation and uplift, thus forming low coral islands.
The orientation of most of the atolls, like that of the atoll chains themselves, is from northwest to southeast although the Îles du Roi Georges group sits at right angles to the main group with its atolls orientated northeast to southwest; Amanu, Takume and Raroia also share this atypical orientation.
Geographically the archipelago can be divided into 9 unofficial groupings: (1) A North West Group: Ahe, Apataki, Arutua, Kaukura, Makatea, Manihi, Mataiva, Rangiroa, Takapoto, Takaroa, Tikehau and Tikei. Historically, some of these have been grouped further into smaller units — the Îles du Roi Georges (Ahe, Manihi, Takapoto, Takaroa, Tikei) and the Îles Palliser (which also includes some atolls of the Centre West grouping). The central region of the archipelago can be split into a (2) Centre West Group: Anaa, Aratika, Faaite, Fakarava, Haraiki, Hikueru, Hiti, Katiu, Kauehi, Makemo, Marutea Nord, Motutunga, Niau, Nihiru, Raraka, Reitoru, Taenga, Tahanea, Taiaro, Tekokota, Tepoto Nord, Toau and Tuanake; and a (3) Centre East Group: Ahunui, Akiaki, Amanu, Fakahina, Fangatau, Hao, Manuhangi, Marokau, Nengonengo, Nukutuvake, Paraoa, Pinaki, Ravahere, Rekareka, Takume, Tauere, Vahitahi and Vairaatea. Two smaller groupings lie to the east away from the NW-SE running chains of the main body of the Tuamotu's: (4) Îles du Desappointement in the extreme northeast: Napuka, Pukapuka and Tepoto Sud; and the (5) East Group: Pukarua, Reao and Tatakoto. In the far southwest corner of the archipelago are the (6) Îles de Duc de Gloucester: Anuanuraro, Anuanurunga, Hereheretue and Nukutepipi. In the south of the archipelago are (7) the South Group: Fangataufa, Marutea Sud, Morane, Mururoa, Tematangi, Tureia and Vanavana; and to the east the (8) Acteon Group: Tenararo, Vahanga, Tenarunga, and Matureivavao. Further south still are the (9) Îles Gambier: Mangareva, Maria Est and Temoe
The atolls and coral islands of the Tuamotu Archipelago represent the reef topped summits of steep-sided seamounts. These emergent seamounts, part of the Tuamotu Seamount Trail, are of small to intermediate size — typical volumes are in the range of 1,000 km³ to 8,000 km³, rising from between 1,500 m to to nearly 4,000 m above the surrounding ocean floor. The seamounts themselves rise from an extensive northwest to southeast trending ridge, known as the Tuamotu Plateau. Plate ages of 65 million years are found in the northwest around atolls such as Tikehau and Maitava. Plate ages tend to decrease towards the southeast and east, with an age of 36 million years being found at Reao, in the far eastern reaches of the archipelago.
Politically the archipelago is split into 17 communes: in the west: Rangiroa, Takaroa, Manihi, Arutua and Fakarava; in the centre: Anaa, Makemo, Hikueru, Hao; in the east, Napuka, Pukapuka, Fangatau, Tatakoto, Nukutuvake and Reao; and in the south: Tureia and Gambier.