Author(s): Bruce W. Hayward
For decades teachers, biologists, geographers and interested members of the public have asked for an up-to-date account of how Northland, Auckland and the Coromandel Peninsula and their landforms were formed. Here, for the first time, is an accessible account designed to be of interest to all levels of understanding.
Almost all of the older rocks were deposited as sediment or erupted as lava on the floor of the ancient Pacific Ocean. Some were plastered onto the coastal edge of Gondwana, and at least 100,000 km3 of these rocks were pushed up out of the ocean and slid onto Northland, about 20 million years ago. About the same time, 1 km-thickness of Waitemata sandstones were deposited in a deep-sea basin over Auckland.
Most of the subsequent history of northern New Zealand was dominated by fiery volcanic activity of greater diversity than any area of similar size elsewhere in the world. This included eruptions of andesite stratovolcanoes, giant caldera volcanoes, searing ignimbrite flows, viscous rhyolite domes and at least 200 small basalt volcanoes erupted in seven volcanic fields.
The present-day shape and landforms of the region reflect its more recent history with local uplift, erosion, volcanic activity, construction of New Zealand's largest sand-dune barriers and harbours, and moulding of the coast by the oscillating sea levels during the Ice Ages.
Bruce Hayward is a semi-retired research geologist, paleontologist and marine ecologist, who spent most of his career studying aspects of the natural and human history of northern NZ (as a paleontologist with the NZ Geological Survey, curator of marine invertebrates at Auckland Museum, a James Cook Fellow at Auckland University, and as selfemployed principal of Geomarine Research). He is author or co-author of over 280 peer-reviewed articles and 20 books. He is a past President of the Geological Society of NZ, a former member of the NZ and Auckland Conservation Boards and co-founder of the NZ Geopreservation Inventory and Auckland Geology Club. His work has been recognised with Fellowship of the Royal Society of NZ and Member of NZ Order of Merit.