Geography of Tonga

Located in Oceania, Tonga is an archipelago in the South Pacific Ocean, directly south of Samoa and about two-thirds of the way from Hawaii to New Zealand. It has 169 islands, 36 of them inhabited, are divided into three main groups – Vava'u, Ha'apai, and Tongatapu – and cover an 800-kilometre (500-mile)-long north-south line.

The largest island, Tongatapu, on which the capital city of Nukuʻalofa is located, covers 257 square kilometres (99 sq mi). Geologically the Tongan islands are of two types: most have a limestone base formed from uplifted coral formations; others consist of limestone overlaying a volcanic base.

The climate is tropical with a distinct warm period (December–April), during which the temperatures rise above 32 °C (89.6 °F), and a cooler period (May–November), with temperatures rarely rising above 27 °C (80.6 °F). The temperature increases from 23 to 27 °C (73.4 to 80.6 °F), and the annual rainfall is from 1,700 to 2,970 millimetres (66.9 to 116.9 inches) as one moves from Tongatapu in the south to the more northerly islands closer to the Equator. The average wettest period is around March with on average 263 mm (10.4 in). The average daily humidity is 80%.

Though administratively divided into the three main island groups of Tongatapu, Ha'apai, and Vava'u (excluding the outlying islands), the Tonga archipelago is actually made of two geologically different parallel chains of islands.

The western islands, such as 'Ata, Fonuafo'ou, Tofua, Kao, Lata'iki, Late, Fonualei, Toku, Niuatoputapu, and Tafahi, make up the Tongan Volcanic Arch and are all of volcanic origin. They were created from the subduction of the western-moving Pacific plate under the Australia-India plate at the Tonga Trench. The Tongan Islands sit on the Australia-India plate just west of the Tonga Trench. These volcanoes are formed when materials in the descending Pacific plate heat and rise to the surface. There is only limited coral reef development on these islands, except for Niuatoputapu.

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