The Cook Islands are in the South Pacific Ocean, north-east of New Zealand, between French Polynesia and American Samoa. There are fifteen major islands, spread over 2.2 million square kilometres of ocean, divided into two distinct groups: the Southern Cook Islands, and the Northern Cook Islands of coral atolls. - The islands were formed by volcanic activity; the northern group is older and consists of six atolls (sunken volcanoes topped by coral growth). The climate is moderate to tropical. The 15 islands and two reefs are grouped as follows: