Millennium Atoll/Caroline Atoll

Millennium Atoll, Line Islands

Millennium (formerly known as Caroline Island) is located in the southern group of the Line Islands, being the easternmost island in the Line Islands chain. The islands of Vostok and Flint are located 232 km to the west and 230 km to the southwest, respectively; Kiritimati is situated around 1,500 km to the northwest. Millennium is an atoll formation with an elongated, slightly crescentic, shape measuring 9.7 km in length and 2.3 km in width.

On the reef rim there are 39 islets — South Island (104 ha), the 4.2 km-long Long Island (76 ha) and Nake Islet (107 ha) being the largest — with a combined area of 3.9 km². They enclose a 9 km long, shallow lagoon that is 5-7 m in depth and up to 500 m across. Within the lagoon are numerous coral heads and patch reefs — some of which form east-west barriers across the lagoon. The surrounding reef flats — averaging 500 m in width — are continuous around the perimeter of the atoll with no reef-crossing passage connecting the interior waters of the lagoon with the surrounding ocean. Instead water exchange takes place via numerous spillways as the tides rise and fall.

The major islets of Millennium Atoll are Nake Island in the north, Long Island in the northeast, and South Island in the far south. The minor islets (see photo map) can be arranged into four groupings: The South Nake Islets (7 islets located on the northwest side of the atoll) consisting of Pandanus Islet (7.2 ha), Danger Islet (2.7 ha), Booby Islet, Coral Islet (1.7 ha), Lone Palm Islet (2 ha), Motu Kota, and Motu Mouakena (1 ha); the Central Leeward Islets (11 islets located on the central west coast) consisting of Motu Mannikiba (21.5 ha), Blackfin Islet (2.6 ha), Motu Matawa (1.7 ha), Emerald Isle (8.3 ha), Shark Islet (8 ha), Scarlet Crab Islet, Motu Nautonga, Azure Isle, Reef-Flat Islet, Bird Islet (4 ha) and Fishball Islet; the Southern Leeward Islets (5 islets located on the southwestern reef rim) consisting of Motu Raurau (3.5 ha), Motu Eitei (1.4 ha), Pisonia Islet (2.4 ha), Motu Kimoa (1.8 ha) and Motu Ana-Ana (2.1 ha); the southeastern and central eastern side of the atoll is occupied by the 13 islets that comprise the Windward Islets of Tridacna Islet (9 ha), Arundel Islet (7.3 ha), North Arundel Islet, Brothers Islet (4.3 ha), North Brothers Islet (1.7 ha), Skull Islet, Pig Islet (7.2 ha), North Pig Islet (5.4 ha), Motu Atibu, Crescent Islet (3.1 ha), Windward Islet (11.4 ha) and Bosun Bird Islet. (Note that most of the islet names are of very recent origin).

Most of the islets of Millennium Atoll are flat and densely vegetated with forests of Pisonia grandis, Cordia subcordata and Heliotrope (Tournefortia argentea)— representing some of the most intact and largest forests of these species remaining in the Pacific. Other areas of the atoll have scrub-type vegetation. The islets are internationally important as major seabird breeding sites, and Millennium, together with Flint, have some of the world’s largest populations of the terrestrial Coconut Crab (Birgus latro).

Synonyms: Caroline Island

image: earth sciences and image analysis laboratory, nasa johnson space center