Cook Islands
The Cook Islands are a remote group of 15 islands and atolls spread over 1,400 km of the south Pacific Ocean,
located between the Society Islands of French Polynesia (on the east) and
Tonga (to the west). The islands are geographically split into two groups — the Northern and Southern
groups with a total land area of 241 km² — scattered over nearly 2 million km² of ocean. The
islands lie nearly 3,400 km northeast of New Zealand, under which the Cook Islands exist as an independent
territory.
The Southern Group — Atiu (27 km²), Aitutaki (19 km²), Mangaia (52 km²), Manuae
(6.2 km²), Mauke (20.3 km²), Mitiaro (22.8 km²), Palmerston (2 km²), Rarotonga (67 km²),
and Takutea (1.2 km²) — has the Cooks Islands largest islands.
They
consist of a mix of high, rugged volcanic islands, raised coral islands and atolls. All members of the southern
Group are inhabited except Manuae and Takutea.
Located around 1,000 km to the north of the southern islands are the Northern Group — Manihiki (5.4 km²), Nassau (1.2 km²), Penrhyn (10 km²), Pukapuka (4.3 km²), Rakahanga (4.1 km²), and Suwarrow (1.7 km²) — which, with the exception of the low coral island of Nassau, are all small to medium sized atoll formations. In comparison to the Southern Cook Islands they are isolated and much less developed.
Geologically the Northern and Southern groups are two separate entities having different geological histories. The Southern Cook Islands are related to the Tubuai Islands (Austral Islands) further to the southeast, forming part of the twin overlapping chains that form the Cook-Austral chain of seamounts. With the exception of the single active submarine volcano of McDonald seamount at the Tubuai end of the chain, all of the islands that comprise the Cook-Austral chain are extinct volcanoes that rise from depths of over 5,000 m from the ocean floor. Of the southern Cook Islands, only the island of Rarotonga retains any mountainous landforms, the rest having been heavily eroded and subsided in to hilly or low coral islands and atolls.
The northern islands, with the exception of Penrhyn, emerge from a large submarine feature known as the Manihiki Plateau. Rising to around 3,000 m below the surface, and some 2,000 m above the surrounding ocean floor, the Manihiki Plateau is an example of a Large Igneous Province (LIP). It is thought to have formed by volcanic episodes sometime during the Cretaceous peroid (120 million years ago) followed by a period of carbonate sedimentation.
