Skip to content
Archipelago

    Mercury BayNew Zealand

    36°58′S 176°05′E

    Aldermen Islands

    Ruamahua

    The Aldermen Islands are a small group of rocky islets to the southeast of Mercury Bay in the North Island of New Zealand. They are located off the coast of the Coromandel Peninsula, 20 kilometres (12 mi) east of the mouth of the Tairua River.

    View of rocky islets at the Aldermen Islands, New Zealand. Digital copy of a photo taken around 1991.
    View of rocky islets at the Aldermen Islands, New Zealand. Digital copy of a photo taken around 1991.

    Bryndlefly / CC BY-SA 3.0

    Chart

    2 landforms

    Overview

    The Aldermen Islands are a small group of rocky islets to the southeast of Mercury Bay in the North Island of New Zealand. They are located off the coast of the Coromandel Peninsula, 20 kilometres (12 mi) east of the mouth of the Tairua River.

    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. The smaller islands include Big Hump, Little Hump, Nga Horo Island, Half Island and The Spire. Their combined area is 133.5 ha (330 acres). The islands are a forested nature reserve hosting rare species including the tuatara. Access is by permit only. The Aldermen Islands are the remains of eroded Pliocene or Early Pleistocene lava domes that form part of the Whitianga Group. Approximately 18,000 years ago during the Last Glacial Maximum 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 Tairua River flowed south of the features, travelling eastwards towards the Pacific Ocean.

    From Wikipedia, CC BY-SA 4.0

    Census, cataloged

    • Major islands2
    • Minor islands0
    • Islets0
    • Rocks & skerries0

    Major islands

    2

    Also in the area

    53

    Inside the group's outline but not confirmed as members by any source.

    • Middle Island55 m · 0.23 km²
    • Hongiora76 m · 0.16 km²
    • Nga Horo Island10 m · 0.04 km²
    • The Spire61 m · 0.02 km²
    • Unnamed island25 m · 0.02 km²
    • Half Island12 m · 0.01 km²
    • Big Hump45 m · 0.01 km²
    • Unnamed island6 m · 0.8 ha
    • Unnamed island11 m · 0.5 ha
    • Unnamed island2 m · 0.3 ha
    • Unnamed island0.3 ha
    • Unnamed island1 m · 0.2 ha

    Figures

    Comparative heights

    Sea level50 m100 m150 m200 m182 mRuamahuaiti168 mRuamahuanui76 mHongiora61 mThe Spire55 mMiddle45 mBig Hump12 mHalf10 mNga Horo
    High points by island, metres above sea level.

    Islands by area

    0.000010.00010.0010.010.11Ruamahuanui: 0.32 km²RuamahuanuiRuamahuaiti: 0.25 km²RuamahuaitiMiddle: 0.23 km²MiddleHongiora: 0.16 km²HongioraNga Horo: 0.04 km²Nga HoroThe Spire: 0.02 km²The SpireUnnamed island: 0.02 km²Unnamed islandHalf: 0.01 km²HalfBig Hump: 0.01 km²Big HumpUnnamed island: 0.8 haUnnamed islandUnnamed island: 0.5 haUnnamed islandUnnamed island: 0.3 haUnnamed islandUnnamed island: 0.3 haUnnamed islandUnnamed island: 0.2 haUnnamed islandUnnamed island: 0.2 haUnnamed islandUnnamed island: 0.1 haUnnamed islandUnnamed island: 0.1 haUnnamed islandUnnamed island: 0.1 haUnnamed islandUnnamed island: 0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed islandLittle Hump: <0.1 haLittle HumpUnnamed island: <0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed islandUnnamed island: <0.1 haUnnamed island
    km², log scale
    Ruamahuanui Island0.32 km²
    Ruamahuaiti Island0.25 km²
    Middle Island0.23 km²
    Hongiora0.16 km²
    Nga Horo Island0.04 km²
    The Spire0.02 km²
    Unnamed island0.02 km²
    Half Island0.01 km²
    Big Hump0.01 km²
    Unnamed island0.8 ha
    Unnamed island0.5 ha
    Unnamed island0.3 ha
    Unnamed island0.3 ha
    Unnamed island0.2 ha
    Unnamed island0.2 ha
    Unnamed island0.1 ha
    Unnamed island0.1 ha
    Unnamed island0.1 ha
    Unnamed island0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Little Hump<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha
    Unnamed island<0.1 ha

    Sources

    Facts

    • Geometry, areas and high points: OpenStreetMap contributors (ODbL), Copernicus GLO-30, via Talus.
    • Wikidata
    • Talus
    • Wikipedia

    Photographs