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Kora : a study of a miocene, submarine arc-stratovolcano, North Taranaki Basin, New Zealand : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science with Honours at Massey University
(Massey University, 1998) Adams, Joshua Donald Busby
Kora is a relict submarine arc-stratovolcano buried offshore in north Taranaki Basin. New Zealand. Kora was active on the seafloor in middle to upper bathyal water depths from the late Early Miocene to Late Miocene times. Post-eruptive burial of the volcanic edifice by Mohakatino Formation and Giant Foresets Formation sediments has preserved the edifice and its flanking volcaniclastic deposits. Arco Petroleum New Zealand Inc. drilled the Kora feature in 1987 and 1988. Core recovered from the Kora-1A, Kora-2, and Kora-3 wells contain lithologies derived entirely from fragmented volcanic rocks, with no evidence for massive lavas or pillow lavas. Typical lithologies are interbedded tuffs, hyaloclastite tuffs, volcanic conglomerates, and tuff breccias. The framework clasts in the tuff breccias and conglomerates are porphyritic andesite lithic clasts and andesite eruptives. The lithics were derived from subvolcanic intrusions that formed prior to the main period of edifice construction between 16 Ma and 12 Ma. The round porphyritic conglomerate framework clasts were shaped in transit through the volcanic conduit during volcanic eruptions. Conglomerates lack a planar clast fabric and have a polymodal matrix. They were deposited as density modified grain flows. The tuff breccias are the suspended tails of these deposits. The interbedded tuffs and sparse pebble trains are interpreted to be suspension deposits derived from primary subaqueous eruptions. The fragmental volcaniclastic rocks erupted from Kora were formed entirely at the water-magma interface from fuel-coolant interactions, and cooling-contraction granulation. In contrast, modern volcaniclastic rocks on the southern Kermadec submarine arc-volcanoes, Rumble IV and Rumble V, commonly form from collapsing proximal pillow lava outcrops and small eruptive vents. Like Kora, epiclastic redeposition of volcaniclastic debris on Rumble IV and Rumble V include avalanche slides, debris flows, and grain flows, with little evidence for large-scale channel deposits. Seismic facies comprising the Kora edifice were determined from seismic reflection profiles. The individual apron facies reflectors are identified. These comprise a downlapping terminal wedge that marks the downslope limit of volcaniclastic debris, or the surface along which they travelled. Long continuous, subparallel, individual apron facies reflectors typify northwestern aspects of Kora; these reflectors can be traced laterally from the crest of the edifice to the long thin terminal wedge at the toe of the edifice. The southeastern aspect consists of individual apron facies reflectors that are hummocky, discontinuous and intertwined, with short thick terminal wedges. The edifice has been subject to a sector collapse on NW slopes, where a slump scar occurs. The eastern slopes dip more steeply than the western slopes. The edifice has a conical morphology and is some 10 - 12 km in diameter. The major element geochemical analyses from Kora have been compared to geochemical anlayses from the Coromandel, Waitakere, Rumble IV, Wairakau, Egmont, Titiraupenga, Alexandra, Kiwitahi, and Tongariro volcanic centres using discriminant function analysis. Results have identified four assemblages of volcanic centres with comparable major element geochemistry. Kora, which fits in to the Waitakere, Wairakau and Alexandra volcanic assemblage is a southward extension of the Northland volcanic "trend".
Economic risk assessment of Mount Egmont : the potential economic implications of a volcanic eruption in Taranaki : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Economics, Massey University, Palmerston North, New Zealand
(Massey University, 2006) Aldridge, Coral Louise
New Zealand is home to a large number of volcanoes, many of which threaten the North Island, with damaging ground hugging hazards or disruptive ash deposits. As little as 2mm of ash will put grazing animals off their feed, completely disrupting the agricultural environment, transport is affected and equipment is vulnerable. The most likely damaging event from an eruption is ash, the potentially unknown area of which is determined by wind direction and strength. The 1995/1996 Ruapehu eruption was geologically considered minor with no more than 10mm of ash deposited, yet the economic consequences and disruption were significant, estimates put the minimum cost of the eruption at $130million made up almost singularly of tourism revenue losses and damage to the hydro-electric turbines. There has been little work completed in assessing economic impact of a natural disaster in an economy prior to the event. While the expected scale of any disaster is frequently assessed on historical evidence for planning purposes, social or economic studies tend to consider vulnerable sectors during evacuation and recovery as opposed to a monetary figure or the economic impact. The most recognised volcanic event (and standard example) in recent history was the Mt St Helens eruption in 1980; this eruption killed 57 people and caused damage in excess of US$1billion. Mt Egmont is the visible headstone of Taranaki's volcanic history but is only the youngest location in a series of destructive volcanoes in the area. There have been no known eruptions within the region since 1755, with eight recorded eruptions in the 300 years prior. It is generally accepted that any future events from Mt Egmont will follow the same path as historic eruptions, explosive ash emissions with gentle lava extrusions. Three eruption scenarios, all skewed towards a more likely smaller eruption, are considered in the overall analysis of the region; future studies may concentrate on rare catastrophic eruptions or the evacuation of New Plymouth. The first scenario is limited largely to the national park with ash fall only within the region, the third scenario pushes ash over much of the North Island and has damaging hazards throughout Taranaki A final consideration is made to investigate how an economy responds to increased volcanic threat without an eruption. If precursors to volcanic activity extend for a long period of time the threat of economic stagnation, reduced investment, emotional stress and permanent relocation from the region will increase. Early warning systems and increased disaster planning has greatly reduced the number of deaths caused by volcanic eruptions, in many ways it has also increased economic vulnerability as danger zones become populated. Taranaki has a low population density with rich natural resources and an economy largely geared towards dairy farming and the extraction of oil and gas. The five largest sectors in Taranaki create $8,910.18million in total output or 57.83% of regional output; these are oil and gas extraction, dairy manufacturing, dairy farming, meat processing and wholesale trade. Oil and gas exploration adds an additional $331.72million to economic output. There is a lot of high level energy infrastructure in Taranaki from gas pipelines connecting fields, production stations and delivery systems to the multitude of high voltage power lines connecting two power generation stations with the national grid. All oil and gas production and much of the gas transmission system is based within Taranaki, this industry alone is estimated to contribute more than $1billion a year to the national economy. One factor of Taranaki's gas monopoly is the significant downstream impact any regional disruption in supply could have on the national economy and social well being. Oil and gas is vital to many aspects of New Zealand business not just within Taranaki but day to day business operations, manufacturing processes and power generation capacity. Iconic industries are those businesses that may have an impact on the local community above that of direct economic loss, that are socially as well as economically significant. These firms are predominantly the largest employers and contributors to the local and national economy, and are the most likely to consider permanent relocation outside the region in the case of a large ongoing event. Research was completed on significant industries to gain a more detailed impression of the largest contributors to the local and national economies and potential disruption. These enterprises include electricity generators and gas production, Fonterra, Ballance, Yarrows and Westgate Port. The National Park, tourism and the airline industry were also considered separately due to their individual importance and likelihood to be affected by an eruption. The results of the input-output scenario analyses show an immediate value added decline in the regional economy ranging between $519.09million and $2,505.21million due to volcanic eruption. Input-output captures the overall regional impact of an eruption, the immediate reduction in output as a result of evacuation and physical influences. However an eruption of any magnitude will also have a national impact on the economy which should not be forgotten. Iconic industries were considered separately to take into account some of the largest regional contributors to the national economy. Risk assessment of the iconic industries enabled the assessment of more long term, wide reaching and national effects of an eruption which are not captured in input-output assessments. The gas industry will have the most detrimental economic effect, literally closing the entire gas dependent manufacturing sector throughout the North Island for a number of weeks. Although the Whareroa dairy factory contributes considerable value to national exports with 100% of production being exported milk volumes normally processed could, with the exception of approximately two weeks during the peak season, be absorbed by other factories in the North Island limiting national impact. It is impossible to determine the degree of flow on effects from all of the businesses affected; many interdependencies wouldn't openly be recognised until they occurred. New Zealand has been lucky in that recent volcanic activity has been minor and sporadic in nature; consequently the public perception of risk has been skewed towards events which in geologic records would not even register. An eruption would overwhelm local civil defence resources almost immediately, the surrounding communities would be flooded with evacuees and the economic ripples would be widely felt. This is particularly the case with Taranaki and the critical high level infrastructure. Mitigating economic risk can only be done by locationally spreading risk, with adequate protection measures (financial or physical) and by increasing public awareness.
The palynology of two Whangarei craters, Northland, New Zealand : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Geography at Massey University, New Zealand
(Massey University, 2013) Gates, Shirley May
Whangarei lies within the Puhipuhi-Whangarei Volcanic Field, one of two fields located in Northland. The purpose of this project was to use a palynological study to provide information on the minimum ages of the young Whangarei cones, their vegetation history, and the approximate date of human arrival. Wetlands in the craters of the Maungatapere and Rawhitiroa basaltic cones were selected for this study since they both occupy discrete areas which only collect sediment from within their respective cones. A single peat core from each wetland was processed for fossil pollen and radiocarbon dating. Radiocarbon dating was performed by the University of Waikato, providing minimum ages for the volcanoes. The date for the base of the Maungatapere core was 10530 ± 136 cal. yr BP, and an age of 2775 ± 52 cal. yr BP was determined for the basal peat from Rawhitiroa. K-Ar dating performed previously indicated that these cones were about 0.30 my old. The pollen data indicated that a kauri-conifer-broadleaved forest was consistently present around Whangarei during the Holocene. At Maungatapere the arrival of Maori at c. 1360 AD was inferred from the marked decrease in Dacrydium cupressinum and the appearance of new species. This was an important horticultural site and was not repeatedly burned. At Rawhitiroa, the arrival of Maori possibly at c. 1200 AD was indicated by a decline in forest trees and the increased abundance of Pteridium esculentum and charcoal fragments. This occurred prior to the deposition of the Kaharoa Tephra, the presence of which was noted in the Rawhitiroa core. The Maungatapere wetland is currently a fertile swamp forest while the Rawhitiroa wetland is an infertile bog dominated by Sphagnum and sedges. The difference in the fertility of the two wetlands can be partially attributed to the activities of humans. Repeated forest fires at Rawhitiroa increased waterlogging and stimulated the growth of herbaceous wetland vegetation, causing the rapid build-up of peat and infertile conditions. The forest at Maungatapere was not repeatedly burned and the wetland became drier over time, maintaining its fertility. The incomplete core of peat infill at Maungatapere was a limitation of this project.
Physical and social impacts of past and future volcanic eruptions in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Earth Science, Massey University, Palmerston North, New Zealand
(Massey University, 1997) Johnston, David Moore
The North Island of New Zealand contains a number of active and potentially active volcanoes. Although the probability of an eruption affecting a significant portion of the North Island is relatively low in any one year, the probability of one occurring in the future is high. The potential impacts of a large eruption are significant and the risk cannot be ignored. The timing of the next eruption cannot yet be determined but its probable effects can reasonably be assessed. The 1945 eruption of Mount Ruapehu dispersed ash over a wide area of the North Island over a period of several months. Individual ash falls were only a few millimetres thick in communities closest to the volcano (<50 km) and trace amounts in communities farther away. Ash falls were mostly of nuisance value in affected communities, causing minor eye and throat irritations, soiling interiors of houses and damaging paintwork. More significant impacts included crop damage, low wool quality on farms close to the mountain, disruption to skiing, the removal of army vehicles from Waiouru and numerous disruptions to water and electricity supplies. The 1995-1996 eruptions caused similar physical effects to the 1945 eruption but had considerably greater social and economic impacts. Over the past 50 years the risk has increased significantly due to an increased population, higher visitor usage and a more technologically advanced infrastructure. With increasing development and population growth the risk from similar or larger eruptions will continue to increase. A community's infrastructure provides the services and linkages which allow society to function. These 'lifelines', involving electricity, water, sewerage and roading. are vulnerable to damage and/or disruption from a range of volcanic hazards. The most threatening hazards include pyroclastic falls, pyroclastic flows and surges, lava extrusions (flows and domes), lahars, debris avalanches and volcanic gases. Unfortunately there are very few quantitative measurements of the impacts of volcanic eruptions on community 'lifelines'. With direct observations of eruption impacts, combined with theoretical considerations, it is possible to form a conceptual model of the likely impacts of a given event. These can then be used to predict likely effects, which may then be utilised in risk analysis (and scenarios). Two eruption scenarios are considered: 1) a 0.1 km3 andesitic eruption of Ruapehu composite volcano during a northwesterly wind, affecting Hastings District; 2) a 4 km3 rhyolitic eruption from the Okataina caldera during a westerly wind, affecting Whakatane District. The choice of scenarios is designed to illustrate the contrast between a disruptive moderate-sized eruption from a cone volcano (Ruapehu) and the destructive impacts of a large caldera eruption (Okataina). The Ruapehu scenario will have disruptive short term impacts on Hastings District, with the recovery process spontaneous, immediate and rapid. The infrastructure of Whakatane will be severely damaged by the Okataina eruption scenario and suffer effects for many years. The social and economic impacts of both scenarios will be determined not only by direct physical consequences but also by the interaction of social and economic factors. Residents of both Whakatane and Hastings were surveyed in February 1995 to measure their understanding of volcanic hazards. This was repeated following the Ruapehu eruptions in November 1995. Few residents have copies of specific volcanic hazard information and few have undertaken any form of information searching prior to the 1995 Ruapehu eruption. The 1995 eruption resulted in a small increase in the numbers searching for information on volcanic hazards in both communities. Although some agencies are perceived as more credible than others as the source of volcanic hazard information, no one agency has a monopoly on perceived credibility (i.e. different people recognise different agencies as the best source of information on volcanic hazard information and warnings). During the 1995 Ruapehu eruption the media (TV, radio and newspaper) were the principal sources of information about what was happening. Different people rely on different channels for information and this should also be acknowledged when issuing warnings and releasing public information. Whakatane and Hastings supply interesting contrasts. Both were subjected to intense media coverage during the 1995 Ruapehu eruption, but Whakatane was spared any direct effects, whereas Hastings experienced the hazard directly, in the form of ash falls in September and October 1995. Only Hastings' respondents showed a significant change in the perceived volcanic threat. However, even though there was no significant change in the perception of volcanic threat in Whakatane, residents still continued to perceive the volcanic threat as being higher than Hastings residents. Experiencing the direct and indirect impacts of the 1995 Ruapehu eruption may make subsequent warnings and information releases more salient, thereby enhancing the likelihood of engaging in protective actions or other forms of response. This is likely to be the case for those individuals and organisations that experienced the greatest impacts. However, the relatively benign impacts may make many prone to a "normalisation bias", whereby individuals or organisations believe that the volcanic eruptions did not affect them negatively, therefore the negative impacts of future volcanic events will also avoid them. This may be prevalent in communities close to Ruapehu which escaped the direct ash falls as a consequence of favourable wind directions. This conclusion suggests that the 1995-1996 Ruapehu eruptions may have both improved and reduced individual, organisational and community preparedness for future volcanic events.
A preliminary Scanning Electron Microscope (SEM) study of magnetite surface microtextures from the Wahianoa moraines, Mt Ruapehu, New Zealand.
(2010-05-11T21:08:23Z) Mandolla, Stephanie; Brook, Martin S
Scanning electron microscope (SEM) of quartz micro‐textures has routinely been used to identify the depositional environment of sediments in areas of former ice‐sheet glaciation. On volcanic mountains, where the geomorphic origin of ridge deposits is often poorly understood, quartz is much less abundant, so SEM analysis has not been used as a depositional discriminator. Preliminary research on surface micro‐textures of abundant magnetite grains from the Wahianoa moraines, south‐eastern Mt Ruapehu, suggests that SEM of magnetite may be useful in determining the process‐origin of deposits. We describe micro‐textures and surface characteristics of samples of magnetite, and our study shows that many of the micro‐textures visible on quartz, thought to be diagnostic of glacial transport, are present on magnetite too. However, evaluating whether SEM analysis of magnetite is an applicable technique will require a better understanding of the microtextures occurring on known glacial, fluvioglacial and aeolian deposits on volcanic mountains.
A sedimentological and geochemical approach to understanding cycles of stratovolcano growth and collapse at Mt Taranaki, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Earth Science at Massey University, Palmerston North, New Zealand
(Massey University, 2008) Zernack, Anke Verena
The long-term behaviour of andesitic stratovolcanoes is characterised by a repetition of edifice growth and collapse phases. This cyclic pattern may represent a natural frequency at varying timescales in the growth dynamics of stratovolcanoes, but is often difficult to identify because of long cycle-timescales, coupled with incomplete stratigraphic records. The volcaniclastic ring-plain succession surrounding the 2 518 m Mt. Taranaki, New Zealand, comprises a wide variety of distinctive volcanic mass-flow lithofacies with sedimentary and lithology characteristics that can be related to recurring volcanic cycles over >190 ka. Debrisflow and monolithologic hyperconcentrated-flow deposits record edifice growth phases while polylithologic debris-avalanche and associated cohesive debris-flow units were emplaced by collapse. Major edifice failures at Mt. Taranaki occurred on-average every 10 ka, with five events recognised over the last 30 ka, a time interval for which stratigraphic records are more complete. The unstable nature of Mt. Taranaki mainly results from its weak internal composite structure including abundant saturated pyroclastic deposits and breccia layers, along with its growth on a weakly indurated and tectonically fractured basement of Tertiary mudstones and sandstones. As the edifice repeatedly grew beyond a critical stable height or profile, large-scale collapses were triggered by intrusions preceding magmatic activity, major eruptions, or significant regional tectonic fault movements. Clasts within debris-avalanche deposits were used as a series of windows into the composition of previous successive proto-Mt Taranaki edifices in order to examine magmatic controls on their failure. The diversity of lithologies and their geochemical characteristics are similar throughout the history of the volcano, with the oldest sample suites displaying a slightly broader range of compositions including more primitive rock types. The evolution to a narrower range and higher-silica compositions was accompanied by an increase in K2O. This shows that later melts progressively interacted with underplated amphibolitic material at the base of the crust. These gradual changes imply a long-term stability of the magmatic system. The preservation of similar internal conditions during the volcano’s evolution, hence suggests that external processes were the main driving force behind its cyclic growth and collapse behaviour and resulting sedimentation pattern.
Eruption cycles and magmatic processes at a reawakening volcano, Mt. Taranaki, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Earth Science at Massey University, Palmerston North, New Zealand
(Massey University, 2008) Turner, Michael Bruce
Realistic probabilistic hazard forecasts for re-awakening volcanoes rely on making an accurate estimation of their past eruption frequency and magnitude for a period long enough to view systematic changes or evolution. Adding an in-depth knowledge of the local underlying magmatic or tectonic driving processes allows development of even more robust eruption forecasting models. Holocene tephra records preserved within lacustrine sediments and soils on and surrounding the andesitic stratovolcano of Mt. Taranaki (Egmont Volcano), New Zealand, were used to 1) compile an eruption catalogue that minimises bias to carry out frequency analysis, and 2) identify magmatic processes responsible for variations in activity of this intermittently awakening volcano. A new, highly detailed eruption history for Mt. Taranaki was compiled from sediment sequences containing Holocene tephra layers preserved beneath Lakes Umutekai and Rotokare, NE and SE of the volcano’s summit, respectively, with age control provided by radiocarbon dating. To combine the two partly concurrent tephra records both geochemistry (on titanomagnetite) and statistical measures of event concurrence were applied. Similarly, correlation was made to proximal pyroclastic sequences in all sectors around the 2518 m-high edifice. This record was used to examine geochemical variations (through titanomagnetite and bulk chemistry) at Mt. Taranaki in unprecedented sampling detail. To develop an unbiased sampling of eruption event frequency, a technique was developed to distinguish explosive, pumice-forming eruptions from dome-forming events recorded in medial ash as fine-grade ash layers. Recognising that exsolution lamellae in titanomagnetite result from oxidation processes within lava domes or plugs, their presence within ash deposits was used to distinguish falls elutriated from blockand- ash flows. These deposits are focused in particular catchments and are hence difficult to sample comprehensively. Excluding these events from temporal eruption records, the remaining, widespread pumice layers of sub-plinian eruptions at a single site of Lake Umutekai presented the lowest-bias sampling of the overall event frequency. The annual eruption frequency of Mt. Taranaki was found to be strongly cyclic with a 1500-2000 year periodicity. Titanomagnetite, glass and whole-rock chemistry of eruptives from Mt. Taranaki’s Holocene history all display distinctive compositional cycles that correspond precisely with the event frequency curve for this volcano. Furthermore, the largest known eruptions from the volcano involve the most strongly evolved magmas of their cycle and occur during the eruptive-frequency minimum, preceding the longest repose intervals known. Petrological evidence reveals a two-stage system of magma differentiation and assembly operating at Mt. Taranaki. Each of the identified 1500-2000 year cycles represent isolated magma batches that evolved at depth at the base of the crust before periodically feeding a mid-upper crustal magma storage system.

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