The Tauranga Volcanic Centre is a geologic region in

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

Bay of Plenty The Bay of Plenty ( mi, Te Moana-a-Toi) is a region of New Zealand, situated around a bight of the same name in the northern coast of the North Island. The bight stretches 260 km from the Coromandel Peninsula in the west to Cape Runawa ...

. It extends from the southern end of

Waihi Beach Waihi Beach is a coastal town at the western end of the Bay of Plenty in New Zealand's North Island. It lies 10 kilometres to the east of the town of Waihi, at the foot of the Coromandel Peninsula. The main beach is 10 kilometres long. The town ...

and from the old volcanoes of the

Coromandel Peninsula The Coromandel Peninsula ( mi, Te Tara-O-Te-Ika-A-Māui) on the North Island of New Zealand extends north from the western end of the Bay of Plenty, forming a natural barrier protecting the Hauraki Gulf and the Firth of Thames in the we ...

that make up the northern part of the

Kaimai Range The Kaimai Range (sometimes referred to as the ''Kaimai Ranges'') is a mountain range in the North Island of New Zealand. It is part of a series of ranges, with the Coromandel Range to the north and the Mamaku Ranges to the south. The Kaimai Ra ...

, towards the

Taupō Volcanic Zone The Taupō Volcanic Zone (TVZ) is a volcanic area in the North Island of New Zealand that has been active for the past two million years and is still highly active. Mount Ruapehu marks its south-western end and the zone runs north-eastward thro ...

. It was the site, about 2.1 million years ago, of the large single eruption event of Waiteariki ignimbrite with

DRE DRE may refer to: * ''Dre'' (album), 2010 by American rapper Soulja Boy Tell 'Em, 2010 * Dre (name) **Dr. Dre, American rapper and producer * DRE voting machine * Digital rectal examination, in medicine * Director of religious education; for exam ...

of .

Geology

The Tauranga Volcanic Centre is at the intersection of the

Hauraki Hauraki is a suburb located on the southern North Shore of Auckland, the largest metropolitan city in New Zealand. It is under the local governance of the Auckland Council. History The traditional name for the western coastline in Hauraki wa ...

and Taupō Rifts and was active during a period of tectonic transition from 2.95 to 1.9 million years ago when major volcanism moved south in

Zealandia Zealandia (pronounced ), also known as (Māori) or Tasmantis, is an almost entirely submerged mass of continental crust that subsided after breaking away from Gondwanaland 83–79 million years ago.Gurnis, M., Hall, C.E., and Lavier, L.L., ...

from the Coromandel Volcanic Zone. It thus has importance geologically as a region of transition, previously classified as part of the Central Volcanic Region, which appears to have commenced as early as 4.5 million years ago from compositional analysis of sea floor eruptives. Part of it to the north west is sometimes defined separately in the literature as the Kaimai Volcanic Centre. However this now seems an artificial distinction as the activity and volcanic rock types over lap in time and type. For example the Waiteariki Formation is

ignimbrite Ignimbrite is a type of volcanic rock, consisting of hardened tuff. Ignimbrites form from the deposits of pyroclastic flows, which are a hot suspension of particles and gases flowing rapidly from a volcano, driven by being denser than the surrou ...

whose associated

tephra Tephra is fragmental material produced by a volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, they rem ...

must almost certainly have come from a now buried super volcano event at the north eastern margins of the old Taupō Rift, and it makes up much of the southern Kaimai Range where not covered by younger rhyolite. The Omanawa Caldera is inferred by an area of

gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...

and

magnetic anomaly In geophysics, a magnetic anomaly is a local variation in the Earth's magnetic field resulting from variations in the chemistry or magnetism of the rocks. Mapping of variation over an area is valuable in detecting structures obscured by overlying ...

that exists to the north-west of the

Rotorua Caldera The Rotorua Caldera, now in filled with Lake Rotorua, is a large rhyolitic caldera. It is one of several large volcanoes located in the Taupō Volcanic Zone on the North Island of New Zealand. Geography The major regional settlement of Rotorua ...

, and this postulated feature buried perhaps under over a hundred meters of Mamaku ignimbrite from the

defines the southern portion of the Centre The Waiteariki

erupted 2.1 million years ago. but there are at least eight other large eruptions that occurred in the Tauranga Volcanic Centre in its period of activity. Along with the eroded andesitic

stratovolcano A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and per ...

that resulted in the Otawa Formation at least 17

rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral ...

rhyodacite Rhyodacite is a volcanic rock intermediate in composition between dacite and rhyolite. It is the extrusive equivalent of those plutonic rocks that are intermediate in composition between monzogranite and granodiorite. Rhyodacites form from rapid ...

lava dome complexes contribute to what has been called the Minden rhyolite subgroup. To add complexity, like presently found in currently active caldera complexes in the

, are the distinct Papamoa ignimbrite formations (dated to 2.21 ± 0.1 million years ago) and a small

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

lava flow on

Matakana Island Matakana Island is located in the western Bay of Plenty in New Zealand's North Island. A long, flat barrier island, it is in length but rarely more than wide. The island has been continuously populated for centuries by Māori tribes that ar ...

(dated to 2.7 ± 0.1 million years ago).

Mount Maunganui Mount Maunganui (, ) is a major residential, commercial and industrial suburb of the Tauranga metropolitan area, located on a peninsula to the north-east of Tauranga's city centre. It was an independent town from Tauranga until the completio ...

that forms one of the heads of the main entrance to

Tauranga Harbour Tauranga Harbour is the natural tidal harbour that surrounds Tauranga CBD and the Mount Maunganui area of Tauranga, New Zealand, and which flows into the Pacific Ocean at Mount Maunganui. The harbour is effectively two flooded river systems separ ...

erupted 2.35 ± 0.06 million years ago and is the most recognised volcano of the Centre but other volcanoes nearby have been used as

Pā The word pā (; often spelled pa in English) can refer to any Māori village or defensive settlement, but often refers to hillforts – fortified settlements with palisades and defensive terraces – and also to fortified villages. Pā sites o ...

s by the

Māori Māori or Maori can refer to: Relating to the Māori people * Māori people of New Zealand, or members of that group * Māori language, the language of the Māori people of New Zealand * Māori culture * Cook Islanders, the Māori people of the C ...

. Compositional analysis has linked the Maungatūtū/Mount Misery dome that is dated to 2.69 ± 0.03 Ma to the younger nearby undated Greenpark and Pukunui rhyolite domes. The Otawa stratovolcano erupted first as long ago as 2.95 million years ago south of

Tauranga Tauranga () is a coastal city in the Bay of Plenty region and the fifth most populous city of New Zealand, with an urban population of , or roughly 3% of the national population. It was settled by Māori late in the 13th century, colonised by ...

. It has hornblende and pyroxene basaltic andesite to dacite lavas and breccias with a present area of . The most northern Bowentown dome is assigned to the Centre tentatively which has the advantage of a possible separation of about 2 million years in known activity of the Coromandel Volcanic Zone to its north from that of the Tauranga Volcanic Centre. Minden Peak may have erupted most recently of all the volcanoes in the Centre.

Relations to other volcanic activity

At the same approximate time the Centre was active to its west in

the

Alexandra Volcanic Group The Alexandra Volcanic Group (also known as Alexandra volcanic lineament or Alexandra Volcanics) is a chain of extinct calc-alkalic basaltic stratovolcanoes that were most active between 2.74 to 1.60 million years ago but is now known to have ha ...

was active. Mount Mounganui 02 (5644342378).jpg,

from Moturiki Island Tauranga Harbour - Matakana Island.jpg,

in foreground and

in background (view towards the west) KaimaiPICT6700.jpg, At this location of the

the communication centre is close to the rhyolite Te Weraiti vent. Attack at Gate Pā.jpg, Volcanoes of the Tauranga Volcanic Centre provide the backdrop for the Gate Pā battle of the

Tauranga campaign The Tauranga campaign was a six-month-long armed conflict in New Zealand's Bay of Plenty in early 1864, and part of the New Zealand Wars that were fought over issues of land ownership and sovereignty. The campaign was a sequel to the invasion of ...

. Anzac Bay from Bowentown.jpg, Bowentown volcanic formations above the beach Tauranga Harbour and City.jpg, Essentially all the land except the foreshore in this view of

is volcanic and most is contributed to by the Tauranga Volcanic Centre with its high hills at either side except at centre where Mamaku ignimbrite from the

has flowed from the horizon down to the waters edge. View to Mount.jpg, The view from the Papamoa Hills towards

taking in the Papamoa ignimbrite formations and that includes the Upuhue and Mangatawa vents.

References

{{Reflist, 33em Rift volcanoes Taupō Volcanic Zone Supervolcanoes VEI-7 volcanoes Pleistocene calderas Calderas of New Zealand Volcanoes of the Bay of Plenty Region Stratovolcanoes of New Zealand Volcanism of New Zealand