Rangitoto Island

is visible here from the air Rangitoto formed during two phases of eruptions that may have lasted only 5–10 years, about 600 years ago. The first part of the eruption sequence, dated by radiocarbon methods at about years ago (= 553 ± 7 yrs BP) was initially wet and produced surges of volcanic ash that mantled neighbouring Motutapu Island from alkaline olivine basalt eruptives sourced from the north cone area. The later part of the eruption dated at about years ago (= 504 ± 5 yrs BP) was dry and built most of Rangitoto, erupting all the sub-alkaline basaltic lava flows of the shield and the southern scoria cone at the apex that mostly buried the north cone. To test this hypothesis, a deep hole was drilled through the western flank of Rangitoto in February 2014. No supporting evidence for these hypothesised small eruptions up to 1000 yrs before the main eruption of Rangitoto was found. The university scientists did, however, core a thin basalt lava flow within marine sediment dated at 6000 years old, and hypothesised that this was an even earlier eruption from Rangitoto. These headline-grabbing results were controversial and not accepted by all geologists. In 2018 many of the original group of Auckland University geologists reported on their latest research and reinterpretation of the evidence and concluded that Rangitoto only erupted once, about 600 yrs ago, possibly in two phases. The thin lava flow within 6000 yr-old sediment in the Rangitoto drillcore has exactly the same chemistry as the lowest/oldest flows of the cored shield volcano above and has recently been shown to also have the same U-Th-Ra signature and both must have been erupted and solidified at virtually the same time. The thin "flow" is therefore likely to be basalt lava that was intruded into the sediment as the shield volcano was starting to be formed. This is similar to the situation seen on the coast at Queen Victoria Rock, near the Rangitoto Lighthouse, where lava flows have ploughed into the soft seafloor sediment and intruded into it, bringing at least one sediment slab up to high tide level. Thus no evidence has been found so far to support the hypotheses of earlier eruptions of Rangitoto between 620 and 8000 yrs ago. It is possible that Rangitoto buried a smaller and much older and unrelated volcano, a view possibly supported, but certainly not proven, by recent microfossil research from the marine sediments obtained from beneath Rangitoto in the stratigraphic drillhole. Structure The southern cone of Rangitoto Volcano with its own crater likely buries a more northern explosion crater and tuff ring formed during the early wet phase of eruption in the middle of the Waitemata Harbour. ==Biology==

'' growing on Rangitoto Because there are virtually no streams on the island, plants rely on rainfall for moisture. It has the largest forest of pōhutukawa trees in the world, The island is considered especially significant because all stages from raw lava fields to scrub establishment and sparse forests are visible. As lava fields contain no soil of the typical kind, windblown matter and slow breaking-down processes of the native flora are still in the process of transforming the island into a more habitable area for most plants (an example of primary succession), which is one of the reasons why the local forests are relatively young and do not yet support a large bird population. However, the Kākā, a New Zealand-endemic parrot, is thought to have lived on the island in pre-European times. Fallow deer were introduced to Motutapu in 1862 and spread to Rangitoto, but disappeared by the 1980s. The brush-tailed rock-wallaby was introduced to Motutapu in 1873, and was common on Rangitoto by 1912, and the brushtail possum was introduced in 1931 and again in 1946. Both were eradicated in a campaign from 1990 to 1996 using 1080 and cyanide poison and dogs. The eradication campaign did not have a significant effect on bird species diversity and abundance, due to the presence of other predators. Stoats, rabbits, mice, rats, cats and hedgehogs remained a problem on the island, but the Department of Conservation (DOC) aimed to eradicate them beginning with the poisoning of black rats, brown rats and mice and in August 2011, both Rangitoto and neighbouring Motutapu Islands were officially declared pest-free with both islands now also boasting populations of newly translocated North Island saddlebacks. As the area is a DOC-administered reserve (in partnership with the tangata whenua Ngāi Tai and Ngāti Paoa), visitors may not take dogs or other animals onto the islands. ==History==

Māori association ,'' Rangitoto Island The volcano erupted within the historical memory of the local Māori iwi (tribes). The name literally means "red sky", and is linked to a traditional story of a fight between Tama-te-kapua, captain of the Arawa canoe, and Hoturoa, captain of the Tainui canoe. The name ("The days of the bleeding of Tama-te-kapua") refers to how Tama-te-kapua was injured in the fight. The peaks of the island were known by the names Ngā Pona Toru o Peretū ("The Three Knuckles of Peretū") or Ngā Tuaitara o Taikehu ("The Dorsal Fins of Taikehu"). Rangitoto is associated with many traditional stories and myths. One involves Tiriwa (the namesake of the traditional name for the Waitākere Ranges, Te Wao Nui o Tiriwa), a chief of the supernatural Tūrehu people, who uplifted Rangitoto from Karekare on the west coast, as a show of his strength. Others involve a 'tupua' couple, children of the Fire Gods. After quarreling and cursing Mahuika, the fire-goddess, they lost their home on the mainland because it was destroyed by Mataoho, god of earthquakes and eruptions, on Mahuika's behalf. Lake Pupuke on the North Shore was created in the destruction, while Rangitoto rose from the sea. The mists surrounding Rangitoto at certain times are called the tears of the tupua for their former home. It was set aside as a recreation reserve in 1890, and became a favourite spot for daytrippers. For over 30 years (from 1898 to 1930), scoria was quarried from near the shoreline on the west side of Islington Bay as building material for Auckland. , From 1925 to 1936, prison labour built roads on the island and a track to the summit. The bay is used by Auckland boat-owners as a refuge, as it is quite sheltered from the prevailing southwest winds. Military installations were built during World War II to support the Auckland harbour defences and to house U.S. troops or store mines. The most visited remains of these installations is the old observation post on the summit. The northern shore of the island was used as a wrecking ground for unwanted ships, and the remains of several wrecks are still visible at low tide. At least 13 ships were wrecked from 1887, the last being the former Wellington and, later, Waiheke ferry, Duchess, in June 1947. (built 1897 - iron deck framing remained in 2014). Other ships include Ngapuhi (1900 - her stern remained in 2014), Jubilee (1857), Arapawa (1908), Rothesay Bay (1877), Gladbrook (ex Countess of Anglesea 1877), Elinor Vernon (1876), Polly (ex Skovland 1891), Columbia (1899 - part of the keel and frame remained in 2014), Dartford (1877) and Rarawa (1903 - the bow, framing, iron plating and stern with two propeller shaft housings were visible above the low water mark in 2014). Baches (small holiday houses) were built around the island's edge in the 1920s and 1930s. The legality of their existence was doubtful from the start and the building of further baches was banned in 1937. Most have since been removed because of the ban and because the island has become a scenic reserve. However, 30 of the 140 baches remain , . The island is close to the Auckland shore. ==Access and tourism==

Regular ferry services and island tours by tractor-trailer are provided by Fullers360 from the Auckland central business district. A boardwalk with around 300 steps allows visitors to reach the summit and enjoy a view of the wooded crater. The distance to the summit is , a one–hour walk by the most direct route. An alternative to walking, a land train, coordinated with the ferry sailings, takes visitors to a short way below the summit. Sea kayak trips from the mainland to the island are also available. There are no campsites on the island, though there is camping at Home Bay on the adjacent Motutapu Island. ==See also==