Puhinui Craters

West of McLaughlin Mt, Auckland's southernmost volcano, there are three small circular mounds made of volcanic ash (tuff cones) each surmounted by a shallow wide explosion crater. These tuff cones were made by a series of small explosive eruptions when magma encountered cold ground water as it rose up towards the surface. The explosions fragmented the country rock overhead and blasted it out of the ground together with some fragmented lava, creating each crater. The material blasted out fell back to the ground and built up each small tuff cone.
The first tuff cone/crater (Pond Crater) you will come across is easily recognised by the pond that now fills its crater. It is beside the access road 100 m or so inside the reserve gate. Its tuff cone mound can be best appreciated from a distance but passes north into a corner of the motorsport park next door.
Further into the park you will see a show jumping arena this is located in the crater of the second tuff cone/crater (named Arena Crater). The flat crater floor has filled with peat that accumulated in a natural swamp and more recently the floor has been drained and slightly widened for use as an arena. The tuff cone is easily recognised rising above the flat floor on the north and south sides but was breached out to the east.
The third tuff cone/crater is aptly named Eroded Crater and lies east of and adjacent to Arena Crater. It is much harder to recognise because the small overflow stream from Arena Crater has flowed right through this crater and created a small deep valley and swamp that obscures the original shape. It is readily identifiable from the detailed contour map.
The time of eruption of these craters is unknown but they may have erupted at the same time as nearby McLaughlin Mt Volcano about 50,000 years ago.

See if you can recognise all three craters and their low surrounding tuff cones.
Which crater has the flattest floor and why do you think this may be the case?
Look at the Auckland Council GIS contour map on-line and switch on contours (under legend) - now can you see the three tuff cones and their craters. You can recognise Eroded Crater by the arc portions of the tuff cone that remain.
https://geomapspublic.aucklandcouncil.govt.nz/viewer/index.html