Chatham Island (Moriori: Rēkohu, lit. 'Misty Sun'; ) is the largest island of the Chatham Islands group, in the south Pacific Ocean off the eastern coast of New Zealand's South Island. It is said to be "halfway between the equator and the pole, and right on the International Date Line", although that point is 173 miles WSW of the island's westernmost point. The island is called Rekohu ("misty skies") in Moriori, and Wharekauri in Māori. The island was named after the survey ship HMS Chatham which was the first European ship to locate the island in 1791. It covers an area of 920 km2. Chatham Island lies 650 km south-east of Cape Turnagain, the nearest point of mainland New Zealand to the island.

Geography

The geography of the roughly T-shaped island is dominated by three features: two bays and a lagoon. More than half of the west coast of Chatham is taken up by the deep indentation of Petre Bay. The island's main settlement of Waitangi is located in a small indentation in Petre Bay's southern coast. Other significant settlements are Kaingaroa on the northeast promontory, and Owenga on the south side of Hanson Bay. On the east coast is the even larger Hanson Bay, which stretches for the entire length of the island (35 km). Much of the area between the bays is taken up by the large Te Whanga Lagoon, which drains to the sea to the east, into the southern half of Hanson Bay. This lagoon covers about 160 km2, and drains several small rivers that rise in the hills at the south end of the island. The next largest lakes are Rangitahi and Huro, respectively northeast and southwest of Te Whanga. The central and north part of Chatham Island are mostly flat, with altitudes ranging from a few metres on the northeast and centre to 50 m on the northwest, but with a few scattered hillocks. The south part is higher, generally sloping down towards north and west; about half of it is over 150 m above sea level. The south coast of the island is mostly cliffs 100 m high or more. The highest point of the island (299 m) lies close to its southernmost point.

Climate

Chatham Island has an oceanic climate (Koppen: Cfb) characterised by a narrow temperature range and relatively frequent rainfall. Their isolated position far from any sizeable landmass renders the record high temperature for the main settlement (Waitangi) just 23.8 C. The climate is cool, wet and windy, with average high temperatures between 15 and 20 °C in summer, and between 5 and 10 °C in July (in the Southern Hemisphere winter). Snowfall is extremely rare, the fall recorded near sea level in July 2015 marking the first such reading for several decades. Under the Trewartha climate classification, Chatham Island has a humid subtropical climate (Cf) for the lack of cold weather during the winter and a daily mean temperature above 10 C for eight months or more.

Flora and fauna

Chatham Island hosts the only known breeding population of the endemic and critically endangered magenta petrel or tāiko (Pterodroma magentae). The seabird was thought to be extinct until 1978, and had a population of under 200 in 2017.

In popular culture

Chatham Island (or "Isle") is featured in the first and in the final chapter of Cloud Atlas, the 2004 novel by David Mitchell. The novel was adapted for screen in 2012.