Geologically the deep magma source and depth of basement are not usual for vents in the area.

[2] In the region of the southern Tama Lakes of the southern Taupō Rift, the tens to hundreds of metre thick Tertiary greywacke basement is shallowest at approximately sea level, being somewhat higher under the volcanoes of Mount Ruapehu and Tongariro.

[3] Lava exists nearby that has been dated to 275,000 years ago, the oldest that contributed to the present Mount Tongariro massive.

[5] The youngest tephra from the Tama Lakes vents is dated to about 11,000 years ago.

[7] Later after further activity at Half cone alone (Waihohonu member of the Mangamate formation) there was again paired activity with this vent by Tama lake area vent(s) over at least 2 months with evidence of explosive magma–groundwater interaction.