Rangitoto Volcano

BY BRUCE HAYWARD (GEOLOGIST)
Accessibility: MODERATE
Beside the track to the summit, the surface of the aa lava flows is rubbly. Photo Bruce Hayward
Youngest volcano in the Auckland Volcanic Field, which erupted 53 small volcanoes in the last 200,000 years.
Rangitoto erupted in two phases about 600 years ago - each phase may have been only a few years apart. Previous hypotheses that Rangitoto started erupting 6000 years ago and in numerous small eruptions since then have been shown to be incorrect.
Inside one of the Rangitoto lava caves. Photo Bruce Hayward.
Rangitoto Volcano is the largest and youngest volcano in the Auckland Volcanic Field. It is the only one known to have erupted in the sea. It consists of a large, circular shield volcano of numerous basalt lava flows with slopes of less than 10 degrees surrounding a central scoria cone complex with slopes of 30 degrees. The youngest scoria cone forms the peak of the island and has a deep central crater out of which the scoria was erupted in fire-fountains of hot frothy lava. The initial eruptions of Rangitoto were into sea water and would have been explosive (phreatomagmatic) producing base surge pyroclastic flows and ash that can now be seen mantling neighbouring Motutapu Island. Any sign of an initial explosion crater and tuff ring, if present, is buried beneath the volcano.
From the summit of Rangitoto there are panoramic views over Auckland and many of its other volcanoes.
A side track off the main track to the summit takes visitors to several lava caves formed within lava flows. As the lava flowed along, the outsides of the lava flow cooled and solidified and molten lava flowed through the centre like water inside a hose. Eventually the supply of lava stopped and the molten centre of the flow drained out leaving behind these lava caves or lava tubes.
West side of Rangitoto. Photo Bruce Hayward
Aucklands largest volcano.
Aucklands best example of a shield volcano (topped by scoria cones)
Auckland's youngest volcano
Probably erupted in at least two phases, several decades apart.
Most easily accessible lava caves in New Zealand
Best example of a'a lava flows in Auckland.
Best example of plant colonisation and succession in Auckland.
Largest pohutukawa forest in the world.
Directions/Advisory

Catch a Fullers Ferry to Rangitoto Wharf from Downtown Auckland or Devonport. Make sure you get back to the wharf in time to catch the last ferry back or else you will be stuck on the island overnight or have to call up an expensive water taxi!

Do not fall over on the track up to the summit as the fresh lava can be sharp. Wear sturdy footwear, not jandals or bare feet. Stay on the track - it is dangerous to walk over the sharp and rubbly lava flow surfaces. In summer take sun tan cream and water to drink as it can get hot crossing the lava flow fields. There is no shop on the island.
If you plan to enter the lava caves take a torch and something to protect your head from being scraped on the unforgiving lava roof.

Google Directions

Click here for Google driving directions

Accessibility: MODERATE

The lower parts of the island are accessible by wheelchair. You can buy a ticket on the tourist tractor train that will take you on a circuit around the island stopping near the top for the more able visitors to climb the stairs and boardwalk to the summit of Rangitoto. The best way to see the island is to take the walking track up to the top from the wharf but the track is a bit rough under foot for those not used to rough terrain and the ascent up the scoria cone is moderately steep.

Features
Volcanic Landform
Geological Age
All of the volcano you can see was erupted about 600 years ago, possibly in two phases a few years apart. Evidence for eruptions extending back 6000 years has now been disproved.
Zealandia Evolution Sequence
Pākihi Supergoup: 5 million years ago – present
Links
References to descriptions of Rangitoto: Hayward, B.W. 2019. Volcanoes of Auckland: A field guide. Auckland University Press, p. 48-61. https://aucklanduniversitypress.co.nz/volcanoes-of-auckland-a-field-guide/ Ballance;P.F.;Smith;I.E.M.;1982. Walks through Auckland's Geological Past: A guide to the geological formations of Rangitoto;Motutapu;and Motuihe Islands. Geological Society of NZ Guidebook 5;24 p. $13 from http://www.gsnz.org.nz/auckland-c-2_12_13.html Hayward;B.W.;Murdoch;G.;Maitland;G.;2011. Volcanoes of Auckland: The Essential Guide. Auckland University Press. pp.101-105. http://store.press.auckland.ac.nz/volcanoes-of-auckland-the-essential-guide/ Hayward, B.W.; Grenfell, H.R. 2013. Did Rangitoto erupt many times? Geoscience Society of New Zealand Newsletter 11: 5-8. https://www.researchgate.net/publication/258374103_Did_Rangitoto_erupt_many_times Hayward, B.W. 2017. Eruption sequence of Rangitoto Volcano, Auckland. Geoscience Society of New Zealand Newsletter 23: 4-10. https://www.researchgate.net/publication/321062566_Eruption_sequence_of_Rangitoto_Volcano_Auckland Homer;L.L.;Moore;P.R.;Kermode;L.O.;2000. Lava and strata: A guide to the volcanoes and rock formations of Auckland. Landscape Publications;Wellington. p.30-33.;