Alexandra Volcanic Group

[3] The arc-type lavas of the Alexandra Volcanic Group are mainly ankaramite, a type of basalt found typically in some South Pacific Ocean Islands and not within continental crust.

[7] Pirongia has at least six edifice-forming vents separated by features including those resulting from large volume collapse events.

[2][8] The second stage was confined to Pirongia and consisted of basaltic eruptions between 1.6 and 0.9 million years ago during the period that the South Auckland volcanic field and Mangakino caldera complex were active.

[1] The arc basalt volcano remnants at Tokanui are a small mound that rises about 30 m (98 ft) within higher rolling hills of the Puketoka and Karapiro Formations.

The lineament then extends into the Hamilton Basin, a major rift-related depression bound by the Waipa Fault Zone with the arc basaltic volcanoes of Pukehoua, Kakepuku, Te Kawa, Tokanui.

This geological map, shows some features of the eastern part of the Alexandra Volcanic Group (pink) and Okete volcanic field (red). The pink areas from the left (west) are Karioi , Pirongia (this map does not distinguish separately Pukehoua and the reference map in the article is more accurate), Kakepuku and Te Kawa
Karioi behind Raglan and Whaingaroa Harbour .
View from the west of Mount Pirongia which is the largest volcano in the Alexandra Volcanic Group . To the left of this view are some of the vents of the Okete volcanic field. The foreground hills over the water of Aotea Harbour are non-volcanic in the Karioi horst block.
Kakepuku with Te Kawa behind.
View towards west of Te Kawa tuff ring , Kakepuku (middle distance) and Pirongia at horizon