The Poor Knights Islands (Māori: Tawhiti Rahi) are a group of islands off the east coast of the Northland Region of the North Island of New Zealand. They lie to the northeast of Whangārei, and offshore halfway between Bream Head and Cape Brett. Uninhabited since the 1820s, they are a nature reserve and popular underwater diving spot, with boat tours typically departing from Tutukaka. The Poor Knights Islands Marine Reserve surrounds the island.
Beaglehole (1955) comments that the origin of the island name is not clear, and speculates that the name could be related to the Poor Knights of Windsor, or that the islands were named for their resemblance to Poor Knight's Pudding, a bread-based dish topped with egg and fried, popular at the time of discovery by Europeans.
Description
The chain consists of two large islands (Tawhiti Rahi, the larger at , and Aorangi () to the south), and several smaller islands. Aorangaia and Archway Island lie to the southwest of Aorangi Island, and there is also a group of smaller rocky islets between the two main islands, the largest of which is Motu Kapiti Island. Others include Bird and Kaka Rock. To the south, there is a smaller island named Ngoio Rock. The Poor Knights Islands are the eroded remnants of a 4-million-year-old rhyolitic volcano that is estimated to have been tall and in diameter.
Oceanography
Spring tide range for the islands is around , decreasing to a neap tide of around . The deep water around the island results in only moderate tidal currents. These are around the same magnitude as the prevailing shelf currents. In the general vicinity of the islands mean flows are around and run toward the southeast.
A remarkable feature of the region is the large internal tides that occur. These are a form of internal wave driven by the local tidal flow forcing the stratification against sloping areas of the shelf face. The surface manifestation of these waves can be seen from space. These waves generate brief highly localised accelerations. Internal wave amplitudes of around have been observed, generating flow speeds as great as .
Geology
The Poor Knights Islands were created in some of the earliest eruptions of the Coromandel Volcanic Zone, between 10 and 9.5 million years ago. The Poor Knights Islands vulcanism represents an early period for the Coromandel Volcanic Zone, as changes in tectonic forces caused the east belt of the Northland Arc (23 to 16 million years ago) to begin moving southwards, and eventually forming the modern Taupō Volcanic Zone.
Environment
The islands are protected as a nature reserve and a permit is required to land or tie boats up. Permits are usually granted only for scientific research. A notable native plant of the islands is the spectacularly flowering Poor Knights lily, which has become a popular garden plant.
Feral pigs, which had roamed Aorangi since the departure of Māori in the 1820s, were exterminated in 1936. The islands have been identified as an Important Bird Area, by BirdLife International because they are home to a breeding population of about 200,000 pairs of Buller's shearwaters.
The islands contain rock arches and sea caves, including Rikoriko Cave, the largest cave in the world by volume, with a cavern measuring and an opening large enough for small tour boats to enter. Rikoriko Cave measures , with a ceiling height of and extends deep below water.
Tawhiti Rahi contains the Northern Arch, Middle Arch, and Maomao Arch, the latter being a popular diving location. Aorangaia Island's east–west rock arch resembles a long tunnel, while the aptly named Archway Island is bisected by two rock arches, with the larger Cathedral Arch about tall.
History
The islands were earlier inhabited by Māori of the Ngāti Wai tribe who grew crops and fished the surrounding sea. The tribe traded with other Maori.