Quaternary Volcanism of the Central Volcanic Region

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Abstract
The main rock types of the Central Volcanic Region of the North Island of New Zealand are distributed in a roughly symmetrical fashion about an axis trending north-north-east from Tongariro National Park to near Maketu on the Bay of Plenty. Adjoining the outer margins of the Region are northward-div,erging greywacke ranges, between which are extensive ignimbrite plateaus. Downfaulting along the inner margins of these plateaus has produced the north-north-east-trending Taupo–Rotorua graben, notable for containing (a) a north-north-east-trending zone of recently active normal faults, which cuts across (b) two main and one minor groups of Quaternary rhyolite domes and associated pumice-breccia deposits. Basaltic rocks lie around the periphery of the rhyolite domes. In the east, Quaternary andesitic cones lie in a north-north-east-trending line along the western edge of the Kaingaroa Plateau; in the west, the cones form a north-trending line close to the eastern edge of the greywacke ranges. The generalised sequence of eruption is andesite (oldest), ignimbrite, rhyolite and dacite, and basalt, although andesite is still being erupted in Tongariro National Park. An assessment of possible future volcanism suggests that activity will probably be confined mainly to the Taupo Volcanic Zone. The main dangers are from the eruption of rhyolite, pumice breccia, and basalt in rhyolite districts and from hydrothermal eruptions in hot spring areas. Further eruptions are expected in Tongariro National Park and along the eastern margin of the Central Volcanic Region. There is a much smaller likelihood of eruption of ignimbrite and dacite. Faulting, especially in the Taupo Volcanic Zone, may continue.

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