The Aldermen Islands are a small group of rocky islets to the southeast of

Mercury Bay Mercury Bay is a large V-shaped bay on the eastern coast of the Coromandel Peninsula on the North Island of New Zealand. It was named by the English navigator Captain James Cook during his exploratory expeditions. It was first named ''Te-Whangan ...

in the

North Island The North Island, also officially named Te Ika-a-Māui, is one of the two main islands of New Zealand, separated from the larger but much less populous South Island by the Cook Strait. The island's area is , making it the world's 14th-largest ...

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

. They are located off the coast of the

Coromandel Peninsula The Coromandel Peninsula ( mi, Te Tara-O-Te-Ika-A-Māui) on the North Island of New Zealand extends north from the western end of the Bay of Plenty, forming a natural barrier protecting the Hauraki Gulf and the Firth of Thames in the we ...

, east of the mouth of the

Tairua River The Tairua River is located on the Coromandel Peninsula in the North Island of New Zealand. It flows north and then northeast for a total of from its source in the Coromandel Range to the west of Whangamatā, passing through the town of Hiku ...

. The islands were named 'the Court of Aldermen' by Captain Cook and his crew on 3 November 1769 after previously naming Mayor Island. The Aldermen group consists of four main islands: Hongiora, Middle, Ruamahuanui, and Ruamahuaiti. Their combined area is . The islands are a forested nature reserve hosting rare species including the

tuatara Tuatara (''Sphenodon punctatus'') are reptiles endemic to New Zealand. Despite their close resemblance to lizards, they are part of a distinct lineage, the order Rhynchocephalia. The name ''tuatara'' is derived from the Māori language and m ...

. Access is by permit only. The Aldermen Islands are the remains of eroded

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Early Pleistocene The Early Pleistocene is an unofficial sub-epoch in the international geologic timescale in chronostratigraphy, being the earliest division of the Pleistocene Epoch within the ongoing Quaternary Period. It is currently estimated to span the time ...

lava dome In volcanology, a lava dome is a circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions on ...

s that form part of the Whitianga Group. Approximately 18,000 years ago during the

Last Glacial Maximum The Last Glacial Maximum (LGM), also referred to as the Late Glacial Maximum, was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent. Ice sheets covered much of Northern North America, Northern Eur ...

when sea levels were over 100 metres lower than present day levels, the islands were hilly features surrounded by a vast coastal plain. Sea levels began to rise 7,000 years ago, after which the islands separated from the rest of New Zealand. When sea levels were lower, the

flowed south of the features, travelling eastwards towards the Pacific Ocean.

References

Uninhabited islands of New Zealand Thames-Coromandel District Islands of Waikato Volcanoes of Waikato Pliocene lava domes Pleistocene lava domes {{Waikato-geo-stub

See also

References