Te Kopua o Matakamokamo/Tank Farm/Tuff Crater

BY BRUCE HAYWARD (GEOLOGIST)
Accessibility: EASY
Tank Farm (Tuff Crater) explosion crater.
One of the least modified explosion craters in the Auckland Volcanic Field.
Tank Farm (Tuff Crater) explosion crater.
This is the middle of three explosion craters at Northcote to Takapuna that are in a line and may have erupted up the same fault line at depth. Eruption of this tuff (layered volcanic ash) ring dammed Wairau Valley, creating a pond and later swamp that was diverted to overflow around the north side of Pupuke volcano and flow to the sea at Milford Beach. Part of the tuff ring near The Warehouse was removed when the northern motorway from the harbour bridge was built. Houses are built inside the crest of the tuff ring. The floor of the crater is in its natural state with intertidal mangroves and salt marsh.
There is confusion over the English name for this volcano - geologists refer to it by its World War 2 title of Tank Farm because fuel tanks were to be located and hidden inside it in the large circular depressions dug along the inside of the northeastern part of the tuff ring. Some person unknown later noticed the name tuff crater beside this crater on Hochstetter's 1864 map of Auckland's volcanoes. Tuff crater was a descriptive term for a tuff ring and explosion crater back then and is written beside a number of similar craters on Hochstetter's map. So this feature was NOT named Tuff Crater by Hochstetter and is a misnomer but the local council has adopted it for the reserve and it has become well entrenched in the local community.
Depressions along the northeast inside of the crater were dug to hide fuel tanks in WW2
Look along the north east side of the tuff ring - how many large circular depressions can you see that were dug for hiding fued tanks?
Walk around the track inside the crater to Exmouth Rd and then back along the tuff ring crest on the roads to get an idea of the size and shape of this volcanic crater.
Why do you think there is no scoria cone in the centre of the crater?
Directions/Advisory

Access to tracks going most of the way around the lagoon on the inside of the crater from the end of St Peters St, Arahia St, Exmouth Rd and The Warehouse Way.

Stay on tracks. Do not attempt to circumnavigate the crater as to get across the entrance channel requires walking on the edge of the motorway bridge. This is illegal and you can be fined.

Accessibility: EASY

Tracks on north and east side are grassed and can be wet in winter. Tracks on north and west side are concreted. Main access is from St Peters St where there are information panels and a viewing terrace.

Features
Volcanic Landform
Geological Age
Probablty erupted about the same time as Onepoto and Pupuke volcanoes, 200,000 years ago.
Zealandia Evolution Sequence
Pākihi Supergoup: 5 million years ago – present
Links
Hayward, B.W. 2019. Volcanoes of Auckland: A field guide. Auckland University Press: p.83-85.. https://aucklanduniversitypress.co.nz/volcanoes-of-auckland-a-field-guide/ See Hayward;B.W.;Murdoch;G.;Maitland;G.;2011. Volcanoes of Auckland: The Essential Guide. Auckland University Press. p.113.;