The Volcanic History of Taranaki

This booklet should be referred to as:- V.E. Neall 1974. 'The Volcanic History of Taranaki'. Published by Egmont National Park Board.

Taranaki Maunga knowen as Mount Egmont and the ranges extending towards New Plymouth have been built by volcanic activity that has lasted from early Pleistocene times (about 2 million years ago) almost to the present day (see Table 1). Prior to this Taranaki was covered by a shallow sea, (e.g., seashell deposits of eastern Taranaki) beneath which a sequence of sediments was being deposited during the Tertiary period (mainly between 12 and 60 million years ago). Oil and gas within these sediments have flowed into structures which have been subsequently drilled and commercially developed e.g. at Kapuni. The lavas which have been extruded from Mt Egmont and the other volcanoes cover a comparatively small area at high altitudes, and below the 900 m contour they merge into a thick apron of fragmentary volcanic debris called the ringplain. Because the latest activity on each volcano destroyed the previous deposits near their source, a complete geological history of the area involves investigations both within and outside the National Park. The outskirts of the Taranaki volcanic ringplains are bounded to the west by the coast and to the east by uplifted Tertiary mudstone country from Urenui south to Hawera.
With time the activity has followed a NNW to SSE trend in Taranaki along an apparent major linear fracture in the earth's crust. Progressing southwards along this fracture each volcano is seen to be associated with a progressively more recent and youthful landscape. From north to south are: (see map, p3) 1. Paritutu and the Sugar Loaves at New Plymouth,
positioned slightly to the north-east of the principal volcanic line.
2. Kaitake, a disembowelled extinct volcano.
3. Pouakai, a severely eroded and extinct volcano, and
4. Egmo nt, a classic volcanic cone of interbedded lavas
and breccias (coarse angular rock fragments set in a matrix).