Poor Knights Islands

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 50 kilometres (31 mi) to the northeast of Whangārei, and 22 kilometres (14 mi) 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.

Historian John Beaglehole (1955) comments that the origin of the islands' 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.

The chain consists of two large islands (Tawhiti Rahi, the larger at 151.5 ha (374 acres), and Aorangi (101 ha (250 acres)) 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 1,000 metres (3,300 ft) tall and 25 kilometres (16 mi) in diameter.

Spring tide range for the islands is around 2 m (6.56 ft), decreasing to a neap tide of around 1 m (3.28 ft). 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 0.2 m/s (0.656 ft/s) 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 100 m (109 yd) have been observed, generating flow speeds as great as 0.5 m/s (1.64 ft/s).

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.

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.