It extends from the southern end of Waihi Beach and from the old volcanoes of the Coromandel Peninsula that make up the northern part of the Kaimai Range, towards the Taupō Volcanic Zone.

It was the site, about 2.1 million years ago, of the large single eruption event of Waiteariki ignimbrite with DRE of 870 ± 87 km3 (209 ± 21 cu mi).

For example the Waiteariki Formation is ignimbrite whose associated tephra must almost certainly have come from a now buried super volcano event at the north eastern margins of the old Taupō Rift, and it makes up much of the southern Kaimai Range where not covered by younger rhyolite.

[2] Along with the eroded andesitic stratovolcano that resulted in the Otawa Formation at least 17 rhyolite-rhyodacite lava dome complexes contribute to what has been called the Minden rhyolite subgroup.

To add complexity, like presently found in currently active caldera complexes in the Taupō Volcanic Zone, are the distinct Papamoa ignimbrite formations (dated to 2.21 ± 0.1 million years ago)[1] and a small basalt lava flow on Matakana Island (dated to 2.7 ± 0.1 million years ago).