Poor Knights Islands
| Tawhiti Rahi (Māori) | |
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| Geography | |
| Location | Northland, New Zealand |
| Coordinates | 35°30′S 174°45′E / 35.500°S 174.750°E |
| Area | 24 km2 (9.3 sq mi) |
| Administration | |
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New Zealand
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The Poor Knights Islands 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 north-east of Whangarei, 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. The Poor Knights Islands Marine Reserve surrounds the island. The islands' name is said to derive from their resemblance to Poor Knight's Pudding, a bread-based dish 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))) with a group of smaller islets between the two, the largest of which is Motu Kapiti. Tawhiti Rahi is also the Māori name for the entire chain, which has a total area of 271 ha (670 acres). The islands are the eroded remnants of a 4-million-year-old rhyolitic volcano.
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 localized 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).
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