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56-567: The Puhipuhi Embayment (also Puhipuhi Basin ) is a volcanic feature in Taupo Volcanic Zone of New Zealand associated with the collapse of the Ōkataina Caldera wall to its west. Its latest significant volcanic eruption was about 31,500 years ago and this dating required a reassessment of recent activity at the Eastern extension of the Tarawera vent alignment. The Puhipuhi Embayment extends from

112-436: A section. The samples are analyzed to determine their detrital remanent magnetism (DRM), that is, the polarity of Earth's magnetic field at the time a stratum was deposited. For sedimentary rocks this is possible because, as they fall through the water column, very fine-grained magnetic minerals (< 17  μm ) behave like tiny compasses , orienting themselves with Earth's magnetic field . Upon burial, that orientation

168-670: A total volume of 78 km (19 cu mi). The central part of the zone is composed of eight caldera centres the oldest of which is the Mangakino caldera which was active more than a million years ago (1.62–0.91 Ma). This produced ignimbrite that 170 km (110 mi) away in Auckland is up to 9 m (30 ft) thick. Other than the now buried Kapenga caldera there are five caldera centres, Rotorua, Ohakuri, Reporoa, Ōkataina and Taupō. These have resulted from massive infrequent eruptions of gaseous very viscous rhyolite magma which

224-813: A zone known as the Taupō Rift. Volcanic activity continues to the north-northeast, along the line of the Taupō Volcanic Zone, through several undersea volcanoes in the South Kermadec Ridge Seamounts , then shifts eastward to the parallel volcanic arc of the Kermadec Islands and Tonga . Although the back-arc basin continues to propagate to the south-west, with the South Wanganui Basin forming an initial back-arc basin, volcanic activity has not yet begun in this region. South of Kaikōura

280-464: Is a long eruptive history with the likelihood that some of the 13 Mangaone Subgroup eruptions were from vents in the embayment and the only dacite eruptives from this centre occur in the south of the embayment. Volcanism within and near such collapse structure embayments associated with the volcanic centre is predominately rhyolitic and Matahina ignimbrite is exposed north of the Tarawera River in

336-431: Is also commonly used to delineate the nature and extent of hydrocarbon -bearing reservoir rocks, seals, and traps of petroleum geology . Chronostratigraphy is the branch of stratigraphy that places an absolute age, rather than a relative age on rock strata . The branch is concerned with deriving geochronological data for rock units, both directly and inferentially, so that a sequence of time-relative events that created

392-548: Is considered its northeastern limit. It forms a southern portion of the active Lau-Havre-Taupō back-arc basin , which lies behind the Kermadec-Tonga Subduction Zone . Mayor Island and Mount Taranaki are recently active back arc volcanoes on the New Zealand extension of this arc. Mayor Island / Tūhua is the northern-most shield volcano adjacent to the New Zealand coast, and is believed to have been active in

448-490: Is estimated to have been ejected in just a few minutes. The date of this activity was previously thought to be 186 AD as the ash expulsion was thought to be sufficiently large to turn the sky red over Rome and China (as documented in Hou Han Shu ), but this has since been disproven. Whakaari / White Island had a major, edifice failure collapse of its volcano dated to 946 BCE ± 52 years. It has been suggested that this

504-510: Is formed from numerous volcanic deposits created by slope failure, eruptions, or lahars . Northwest of Ruapehu is Hauhungatahi , the oldest recorded volcano in the south of the plateau, with to the north the two prominent volcanic mountains in the Tongariro volcanic centre being Tongariro and Ngauruhoe which are part of a single composite stratovolcano . The most likely risk is earthquake associated with multiple active faults, such as within

560-528: Is found in a small cone and lavas that were intruded in to lake sediments and are usually overlain by Mangaone Subgroup tephras and assigned about 1000 years before the Rotoiti eruption as they are overlaid by this as well. Utu ignimbrites are exposed in small outcrops within the Puhipuhi embayment. An example of probably basaltic dyke intrusion that never reached the surface, but propagated towards Mount Tarawera ,

616-411: Is preserved. For volcanic rocks, magnetic minerals, which form in the melt, orient themselves with the ambient magnetic field, and are fixed in place upon crystallization of the lava. Oriented paleomagnetic core samples are collected in the field; mudstones , siltstones , and very fine-grained sandstones are the preferred lithologies because the magnetic grains are finer and more likely to orient with

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672-482: Is rich in silicon , potassium , and sodium and created the ignimbrite sheets of the North Island Volcanic Plateau . The detailed composition suggests subduction erosion might play a predominant role in producing this rhyolite, as later assimilation and fractional crystallization of primary basalt magma, is difficult to model to explain the composition and volumes erupted. This central zone has had

728-451: Is widening east–west at the rate of about 8 mm (0.31 in)/year, while at Mount Ruapehu it is only 2–4 mm (0.079–0.157 in)/year and this increases at the north eastern end at the Bay of Plenty coast to 10–15 mm (0.39–0.59 in)/year. The rift has had three active stages of faulting in the last 2 million years with the modern Taupō rift evolving in the last 25,000 years after

784-470: The Hatepe eruption , occurred in 232 CE. It is believed to have first emptied the lake, then followed that feat with a pyroclastic flow that covered about 20,000 km (7,700 sq mi) of land with volcanic ash . A total of 120 km (29 cu mi) of material expressed as dense-rock equivalent (DRE) is believed to have been ejected, and over 30 km (7.2 cu mi) of material

840-520: The Horomatangi Reefs or Motutaiko Island in Lake Taupō or the lava dome of Mount Tarawera . This later as part of the Ōkataina caldera complex is the highest risk volcanic field in New Zealand to man. Mount Tauhara adjacent to Lake Taupō is actually a dacitic dome and so intermediate in composition between andesite and rhyolite but still more viscous than basalt which is rarely found in

896-561: The Taupō and Rotorua areas and offshore into the Bay of Plenty . It is part of a larger Central Volcanic Region that extends to the Coromandel Peninsula and has been active for four million years. The zone is contained within the tectonic intra-arc continental Taupō Rift and this rift volcanic zone is widening unevenly east–west, with the greatest rate of widening at the Bay of Plenty coast,

952-639: The Taupō Fault Belt , but many faults will be uncharacterised as was the case with the 1987 Edgecumbe earthquake . Earthquakes can be associated with landslides and inland or coastal tsunami that can result in great loss of life and both have happened on the Waihi Fault Zone . The relative low grade volcanic activity of the andesite volcanoes at each end of the zone has resulted in recorded history in both direct loss of life and disrupted transport and tourism. The only high grade eruption in recorded history

1008-472: The Taupō Volcano and the Ōkataina Caldera have had multiple eruptions in the last 25,000 years. The zone's largest eruption since the arrival of Europeans was that of Mount Tarawera (within the Ōkataina Caldera) in 1886, which killed over 100 people. Early Māori would also have been affected by the much larger Kaharoa eruption from Tarawera around 1315 CE. The last major eruption from Lake Taupō,

1064-431: The law of superposition , states: in an undeformed stratigraphic sequence, the oldest strata occur at the base of the sequence. Chemostratigraphy studies the changes in the relative proportions of trace elements and isotopes within and between lithologic units. Carbon and oxygen isotope ratios vary with time, and researchers can use those to map subtle changes that occurred in the paleoenvironment. This has led to

1120-547: The natural remanent magnetization (NRM) to reveal the DRM. Following statistical analysis, the results are used to generate a local magnetostratigraphic column that can then be compared against the Global Magnetic Polarity Time Scale. This technique is used to date sequences that generally lack fossils or interbedded igneous rocks. The continuous nature of the sampling means that it is also a powerful technique for

1176-506: The Ruapehu and Tongariro grabens . The recent deposits from major eruptions and lake features mean many potentially significant faults are uncharacterised, either completely (for example the 6.5 MW 1987 Edgecumbe earthquake resulted in the mapping of the Edgecumbe fault for the first time) or frequency of events and their likely magnitude are not understood. It can not be assumed that just because

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1232-473: The Whakamaru eruption the central part of the zone has dominated, so that when the whole zone is considered there has been about 3,000 km (720 cu mi) of rhyolite, 300 km (72 cu mi) of andesite, 20 km (4.8 cu mi) of dacite and 5 km (1.2 cu mi) of basalt erupted. Less gaseous rhyolite magma dome building effusive eruptions have built features such as

1288-588: The ambient field during deposition. If the ancient magnetic field were oriented similar to today's field ( North Magnetic Pole near the North Rotational Pole ), the strata would retain a normal polarity. If the data indicate that the North Magnetic Pole were near the South Rotational Pole , the strata would exhibit reversed polarity. Results of the individual samples are analyzed by removing

1344-564: The central 50 km (12 cu mi) Pokai eruption of about 275 ka, and the paired Mamaku to the north and east central Ohakuri eruptions of about 240,000 years ago that together produced more than 245 km (59 cu mi) dense-rock equivalent of material. The southern Taupō Volcano Oruanui eruption about 25,600 years ago produced 530 km (130 cu mi) dense-rock equivalent of material and its recent Hatepe eruption of 232 CE ± 10 years had 120 km (29 cu mi) dense-rock equivalent.  Since

1400-422: The distinctive Waiteariki ignimbrite that erupted 2.1 million years ago in a supereruption, presumably from the gravity anomaly defined Omanawa Caldera , is within the postulated borders of the old Taupō Rift. The multiple intra-rift faults are some of the most active in the country and some have the potential to create over magnitude 7 events. The fault structures are perhaps most well characterised related to

1456-667: The eastern margin of Mount Tarawera towards Kawerau including land mostly devoted to the Tarawera Forest portion of the Kaingaroa Forest . The basin is a dissected plateau at about 200 m (660 ft) above sea level. The Tarawera River cuts through the north of the basin and is its drainage. Both the Pupipuhi Embayment and the Tarawera Volcanic Complex are part of the Ōkataina Volcanic Centre . There

1512-496: The embayment, Rotoiti ignimbrite at its southern margins and Kawerau ignimbrite at its centre. The basins Kawerau Ignimbrite is dated to about 31.5 ka and overlies both the much older Matahina ignimbrite (about 280 ka), the relatively recent Rotoiti ignimbrite and also most of the tephras of the 43-31 ka Mangaone Subgroup. Kawerau Ignimbrite is the youngest partially-welded ignimbrite in the Taupō Volcanic Zone . Puhipuhi dacite

1568-512: The gap may be due to removal by erosion, in which case it may be called a stratigraphic vacuity. It is called a hiatus because deposition was on hold for a period of time. A physical gap may represent both a period of non-deposition and a period of erosion. A geologic fault may cause the appearance of a hiatus. Magnetostratigraphy is a chronostratigraphic technique used to date sedimentary and volcanic sequences. The method works by collecting oriented samples at measured intervals throughout

1624-647: The geology of the region around Paris. Variation in rock units, most obviously displayed as visible layering, is due to physical contrasts in rock type ( lithology ). This variation can occur vertically as layering (bedding), or laterally, and reflects changes in environments of deposition (known as facies change). These variations provide a lithostratigraphy or lithologic stratigraphy of the rock unit. Key concepts in stratigraphy involve understanding how certain geometric relationships between rock layers arise and what these geometries imply about their original depositional environment. The basic concept in stratigraphy, called

1680-591: The intra-arc Taupō Rift. As there is presently no absolute consensus with regard to the cause of the Taupō Rift's extension or its exceptional current volcanic productivity, some of the discussion on this page has been simplified, rather than all possible models being presented. Recent scientific work indicates that the Earth's crust below the Taupō Volcanic Zone may be as little as 16 kilometres thick. A film of magma 50 kilometres (30 mi) wide and 160 kilometres (100 mi) long lies 10 kilometres under

1736-413: The largest number of very large silicic caldera-forming eruptions recently on earth as mentioned earlier. During a period of less than 100,000 years commencing with the massive Whakamaru eruption about 335,000 years ago of greater than 2,000 km (480 cu mi) dense-rock equivalent of material, just to the north of the present Lake Taupō , over 4,000 km (960 cu mi) total

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1792-459: The last 1000 years. It is formed from rhyolite magma. It has a quite complex eruptive history but only with one definite significant Plinian eruption . Mount Taranaki is an andesite cone and the most recent of four Taranaki volcanoes about 140 km (87 mi) west of the Taupō Volcanic Zone. Associated with the Taupō volcanic zone, intra-arc extension is expressed as normal faulting within

1848-546: The least at Mount Ruapehu and a rate of about 8 mm (0.31 in) per year at Taupō. The zone is named after Lake Taupō , the flooded caldera of the largest volcano in the zone, the Taupō Volcano and contains a large central volcanic plateau as well as other landforms. There are numerous volcanic vents and geothermal fields in the zone, with Mount Ruapehu , Mount Ngauruhoe and Whakaari / White Island erupting most frequently. Whakaari has been in continuous activity since 1826 if you count such as steaming fumaroles, but

1904-414: The massive Oruanui eruption and now being within two essentially inactive rift systems. These are the surrounding limits of the young Taupō Rift between 25,000 and 350,000 years and old Taupō Rift system whose northern boundary is now located well to the north of the other two being created before 350,000 years ago. The Tauranga Volcanic Centre which was active between 2.95 to 1.9 million years ago, and

1960-575: The modern Taupō Volcanic Zone in what proved to be an evolving classification scheme: Rotorua, Ōkataina, Maroa, Taupō, Tongariro and Mangakino. The old zone almost certainly contains volcanoes in the Tauranga Volcanic Centre . Other important features of the TVZ include the Ngakuru and Ruapehu grabens . There is more recent, somewhat different classification, by some of the same authors, that uses

2016-595: The plate boundary changes to a transform boundary with oblique continental collision uplifting the Southern Alps in the South Island . A subduction zone reappears south-west of Fiordland , at the south-western corner of the South Island, although here the subduction is in the opposite direction. Solander Island / Hautere is an extinct volcano associated with this subduction zone, and the only one that protrudes above

2072-450: The rate of expansion of the rift is greatest near the coast that this is where most significant tectonic earthquakes in terms of human risk will be. The Waihi Fault Zone south of Lake Taupō and associated with the Tongariro graben has a particular risk of inducing massive landslips which has caused significant loss of life and appears to be more active than many other faults in the zone. The north ( Whakatane Graben – Bay of Plenty) part of

2128-437: The rock layers. Strata from widespread locations containing the same fossil fauna and flora are said to be correlatable in time. Biologic stratigraphy was based on William Smith's principle of faunal succession , which predated, and was one of the first and most powerful lines of evidence for, biological evolution . It provides strong evidence for the formation ( speciation ) and extinction of species . The geologic time scale

2184-432: The rocks formation can be derived. The ultimate aim of chronostratigraphy is to place dates on the sequence of deposition of all rocks within a geological region, and then to every region, and by extension to provide an entire geologic record of the Earth. A gap or missing strata in the geological record of an area is called a stratigraphic hiatus. This may be the result of a halt in the deposition of sediment. Alternatively,

2240-463: The same applies to say the Okataina volcanic centre . The Taupō Volcanic Zone has produced in the last 350,000 years over 3,900 cubic kilometres (940 cu mi) material, more than anywhere else on Earth, from over 300 silicic eruptions, with 12 of these eruptions being caldera-forming. Detailed stratigraphy in the zone is only available from the Ōkataina Rotoiti eruption but including this event,

2296-553: The sea. In the North Island rifting associated with plate tectonics has defined a Central Volcanic Region, that has been active for four million years and this extends westward from the Taupō volcanic zone through the western Bay of Plenty to the eastern side of the Coromandel Peninsula . The dominant rifting axis associated with the Central Volcanic Region has moved with time, from the back-arc associated Hauraki Rift to

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2352-406: The specialized field of isotopic stratigraphy. Cyclostratigraphy documents the often cyclic changes in the relative proportions of minerals (particularly carbonates ), grain size, thickness of sediment layers ( varves ) and fossil diversity with time, related to seasonal or longer term changes in palaeoclimates . Biostratigraphy or paleontologic stratigraphy is based on fossil evidence in

2408-472: The surface. The geological record indicates that some of the volcanoes in the area erupt infrequently but have large, violent and destructive eruptions when they do. Technically the zone is in the continental intraarc Taupō Rift, which is a continuation of oceanic plate structures associated with oblique Australian and Pacific Plate convergence in the Hikurangi subduction zone . At Taupō the rift volcanic zone

2464-405: The term caldera complex: Stratigraphy Catholic priest Nicholas Steno established the theoretical basis for stratigraphy when he introduced the law of superposition , the principle of original horizontality and the principle of lateral continuity in a 1669 work on the fossilization of organic remains in layers of sediment. The first practical large-scale application of stratigraphy

2520-778: The timescale of likely warning of such an event. These eruptions are associated with tephra production that results in deep ash fall over wide areas (e.g. the Whakatane eruption of ~ 5500 years ago had 5 mm (0.20 in) ashfall 900 km (560 mi) away on the Chatham Islands ) ` pyroclastic flows and surges, which rarely have covered large areas of the North Island in ignimbrite sheets, earthquakes, lake tsunamis, prolonged lava dome growth and associated block and ash flows with post-eruption lahars and flooding. Download coordinates as: The following Volcanic Centres belong to

2576-458: The zone has been more productive than any other rhyolite predominant volcanic area over the last 50,000 odd years at 12.8 km (3.1 cu mi) per thousand years. Comparison of large events in the Taupō volcanic zone over the last 1.6 million years at 3.8 km (0.91 cu mi) per thousand years with Yellowstone Caldera 's 2.1 million year productivity at 3.0 km (0.72 cu mi) per thousand years favours Taupo. Both

2632-405: The zone is predominantly formed from andesitic magma and represented by the continuously active Whakaari / White Island andesite – dacite stratovolcano. Although Strombolian activity has occurred the explosive eruptions are typically phreatic or phreatomagmatic . The active emergent summit tops the larger, 16 kilometres (9.9 mi) × 18 kilometres (11 mi), submarine volcano with

2688-419: The zone. The southern part of the zone contain classic volcanic cone structure formed from andesite magma in effusive eruptions that cool to form dark grey lava if gas-poor or scoria if gas-rich of this part of the zone. Mount Ruapehu, the tallest mountain in the North Island, is a 150 km (36 cu mi) andesite cone surrounded by a 150 km (36 cu mi) ring-plain. This ring plain

2744-544: Was Earth's most recent eruption reaching VEI-8, the highest level on the Volcanic Explosivity Index . The Rotorua caldera has been dormant longer, with its main eruption occurring about 225,000 years ago, although lava dome extrusion has occurred within the last 25,000 years. The Taupō volcanic zone is approximately 350 kilometres (217 mi) long by 50 kilometres (31 mi) wide. Mount Ruapehu marks its southwestern end, while Whakaari / White Island

2800-425: Was atypically basaltic from Mount Tarawera and although very destructive is not likely to be a perfect model for the more typical and often larger rhyolitic events associated with the Taupō Volcano and the Ōkataina Caldera . As mentioned earlier the Ōkataina caldera complex is the highest risk volcanic field risk in New Zealand to man and the recent frequency of rhyolitic events there is not reassuring, along with

2856-412: Was by William Smith in the 1790s and early 19th century. Known as the "Father of English geology", Smith recognized the significance of strata or rock layering and the importance of fossil markers for correlating strata; he created the first geologic map of England. Other influential applications of stratigraphy in the early 19th century were by Georges Cuvier and Alexandre Brongniart , who studied

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2912-525: Was developed during the 19th century, based on the evidence of biologic stratigraphy and faunal succession. This timescale remained a relative scale until the development of radiometric dating , which was based on an absolute time framework, leading to the development of chronostratigraphy. One important development is the Vail curve , which attempts to define a global historical sea-level curve according to inferences from worldwide stratigraphic patterns. Stratigraphy

2968-495: Was erupted. These eruptions essentially defined the limits of the present central volcanic plateau , although its current central landscape is mainly a product of later smaller events over the last 200,000 years than the Whakamaru eruption. The other volcanic plateau defining eruptions were to the west, the 150 km (36 cu mi) Matahina eruption of about 280,000 years ago, the mainly tephra 50 km (12 cu mi) Chimp (Chimpanzee) eruption between 320 and 275 ka,

3024-401: Was manifest as an earthquake swarm under the embayment during a recent period of volcanic unrest. Taupo Volcanic Zone The Taupō Volcanic Zone ( TVZ ) is a volcanic area in the North Island of New Zealand . It has been active for at least the past two million years and is still highly active. Mount Ruapehu marks its south-western end and the zone runs north-eastward through

3080-419: Was previously classified as part of the Central Volcanic Region, appears now to be in a tectonic continuum with the Taupō Volcanic Zone. Recent ocean floor tephra studies off the east coast of the North Island have shown an abrupt compositional change in these, from about 4.5 million years ago, that has been suggested to distinguish Coromandel Volcanic Zone activity from that of the Taupō Volcanic Zone. Further

3136-472: Was the cause of the tsunami tens of metres tall that went up to 7 kilometres (4.3 mi) inland in the Bay of Plenty at about this time. Although significant tsunami's can be associated with volcanic eruptions, it is unknown if the cause was a relatively small eruption of Whakaari or another cause such as a large local earthquake Taupō erupted an estimated 1,170 km (280 cu mi) of DRE material in its Oruanui eruption 25,580 years ago. This

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