The Whangārei volcanic field (Puhipuhi-Whangarei volcanic field) is an area of intra-plate monogenetic volcanism located near the city of Whangārei,

North Island The North Island, also officially named Te Ika-a-Māui, is one of the two main islands of New Zealand, separated from the larger but much less populous South Island by the Cook Strait. The island's area is , making it the world's 14th-largest ...

, New Zealand. It was last active between 260,000 to 319,000 years ago and continues to be potentially active as a low-velocity seismic zone in the crust exists beneath Whangārei, which is interpreted to be a body of partial melt. This mantle source has been coupled to the lithosphere for about 8 million years. As the field has potentially been active at low frequency for millions of years, with 100,000 years or more between events it might best be regarded as dormant. The recent vents active in the last million years include some dacite in composition. Composition details are freely available for most of the field but many vents do not have ages.

Geology

Volcanics

These volcanoes are part of the eastern Northland volcanic belt which includes the monogenetic Kaikohe-Bay of Islands volcanic field and the volcanoes of the Whangārei Heads and the Hen of the

Hen and Chickens Islands The Hen and Chicken Islands (usually known collectively as the ''Hen and Chickens'') lie to the east of the North Auckland Peninsula off the coast of northern New Zealand. They lie east of Bream Head and south-east of Whangarei with a total ...

which are not part of the field. Rather the volcanoes of the Whangārei Heads are usually related to the now extinct predominantly andesitic Taurikura volcanic complex and its caldera, although the close proximity, overlap in time, and dacite eruptive centres possibly reflects a continuum.

Non-volcanics and tectonics

The hilly landscape to the west of Whangārei is from uplifted Waipapa Terrane greywacke deposits from ocean floor sediments first laid down several hundred millions ago off the coast of Gondwanaland. There are some coal measures, sandstone, and limestone from late Eocene and Oligocene (Te Kuiti Group) sediments laid on top of the greywacke basement. On top of these contributing to many hills are often more clay like deposits originally from the floor of the Pacific Ocean of 80-25 million years ago. About 25 million years ago these deep-sea sediments were uplifted as the

Northland Allochthon New Zealand's Northland Region is built upon a basement consisting mainly of greywacke rocks, which are exposed on the eastern side of the peninsula. In-place Eocene coal measures crop out at Kamo, near Whangarei, and Oligocene limestone crop ...

. There are no known active faults in NorthlandGNS:NZ active fault database
/ref> Historic faults are believed, due to volcanic alignment, to have been permissive to the surface volcanism of the last 25 million years, with the Whangārei Harbour fault being a prominent example.

List of volcanoes

References

{{DEFAULTSORT:Whangarei volcanic field Volcanism of New Zealand Landforms of the Northland Region Whangārei Whangarei District Volcanoes of the Northland Region