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    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.
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    High-precision tephrostratigraphy : tracking the time-varying eruption pulse of Mt. Taranaki, North Island, 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, 2017) Damaschke, Magret
    In this research it was proposed that a more robust record of volcanic activity for Mt. Taranaki (New Zealand) could be derived from tephras (pyroclastic fall deposits) within cores from several lakes and peatlands across a 120o arc, NE-SE of the volcano, covering a range of prevailing down-wind directions. These data were integrated with previous tephrochronology studies to construct one of the longest and most complete volcanic eruption history records ever developed for an andesitic stratovolcano. Using 44 new radiocarbon dates, electron microprobe analysis of glass shard and ttitanomagnetite chemical composition, along with whole-rock chemistry, a chrono- and chemostratigraphy was established. The new record identifies at least 272 tephraproducing eruptions over the last 30 cal ka BP. Six chemo-stratigraphic groups were identified: A (0.5 – 3 cal ka BP), B (3 – 4 cal ka BP), C (4 – 9.5 cal ka BP), D (9.5 – 14 cal ka BP), E (14 – 17.5 cal ka BP), and F (23.5 – 30 cal ka BP). These were used to resolve previous stratigraphic uncertainties at upper-flank (proximal) and ring-plain (medial) sites. Several well-known “marker tephras” are now recognized as being ~2000 years older than previously determined (e.g., Waipuku, Tariki, and Mangatoki Tephra units) with the prominent Korito Tephra stratigraphically positioned above the Taupo-derived Stent Tephra. Further, new markers were identified, including the Kokowai Tephra unit (~4.7 cal ka BP), at a beach-cliff exposure, 40-km north-east of the volcano. Once age-models were established for each tephra, units were matched between sites using statistical methods. Initial statistical integration showed that the immediate past high-resolution tephrochronological record suffered from a distinctive “old-carbon” effect on its ages (Lake Rotokare). This had biased the most recent probabilistic forecasting and generated artificially high probability estimates (52-59% eruption chance over the next 50 years). Once the Rotokare record was excluded and chemostratigraphy constraints were applied, a reliable multi-site tephra record could be built only for the last ~14 ka BP. The new data confirms a highly skewed distribution of mainly (98% of cases) short intervals between eruptions (mode of ~9 years and average interval ~65 years). Long intervals (up to 580 years) as seen in earlier records were reduced to 2% of the record, but can now be considered real, rather than missing data. The new data confirm a cyclic pattern of varying eruption frequency (with a five-fold range in annual frequency) on a period of ~1000-1500 years. The new time-varying frequency estimates suggest a lower probability for a new eruption at Mt. Taranaki over the next 50 years of 33-42%. The newly established chemostratigraphy was further used to investigate time-related compositional changes. Whole-lapilli analyses highlighted that a specific very evolved Ca-rich and Fe-poor composition was only found within the easterly and south-easterly depositional sites. This was explained by eruption of a stratified magma reservoir, which holds greater modal proportions of plagioclase and lower proportions of pyroxene within low-density, gas-rich upper conduit regions. During the most explosive phases of eruptions, when plumes reach the stratospheric jetstream, the lowest-density pumice is thus dispersed by high-level stable westerly winds. Further, two distinct evolutional trends were seen in the long and new tephrochronological record; from 17.5 to 3 cal ka BP and <3 cal ka BP; with wholelapilli, glass, and titanomagnetite compositions overall evolving over time. The former compositional trend indicates a crystallising and cooling magma source in the deep crust, with multiple, spatially separated magma source regions forming, each generating magmas (i.e., magma batches) with unique titanomagnetite compositions. This trend is interrupted by a distinct shift towards less-evolved compositions and the initiation of a second parasitic vent (Fanthams Peak at the southern flank of Mt. Taranaki).
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    The late quaternary cover bed stratigraphy and tephrochronology of north-eastern and central Taranaki, New Zealand : a thesis presented in partial fulfullment of the requirements for the degree of Doctor of philosophy in soil science at Massey University, Palmerston North, New Zealand
    (Massey University, 1989) Alloway, Brent Victor
    This study involved the recognition and description of tephra, lahar and debris avalanche deposits generated from activity centred at Egmont Volcano over the last c.l30kyrs B.P. Stratigraphic relationships between the various cover bed deposits of north-eastern and central Taranaki are discussed and their distributions mapped where possible. The stratigraphic record indicates that tephra emission and lahar inundation are typical, recurring features of Egmont Volcano. Average periodicity for moderate to major sized eruptions (>107m3) may be as frequent as, one every 250 years. Tephras from Egmont Volcano have been correlated to both the adjacent Wanganui and Waikato districts. Six rhyolitic tephras erupted from the Central North Island have been identified in Taranaki and are especially valuable as widespread time planes within the andesitic cover bed succession. At least thirteen lahars are shown to have been deposited over extensive areas of the ring plain during the last 22.5 kyrs B.P. Many of these lahars became channelised within stream and river catchments to extend to the North Taranaki coastline. Partial or complete collapse of Egmont Volcano at c.23kyrs and much earlier at c.100kyrs B.P. generated large volumed, debris avalanches that spread principally over a wide north-eastern to south-eastern arc. The resulting deposits are characterised by extensive areas of mounds now deeply buried by a younger late Pleistocene and Holocene tephra mantle. The stratigraphy of an alternating sequence of reddish (S-units) and yellowish (L-units) medial beds was also investigated. Generally their thinning pattern is similar to that of coarse ash and lapilli suggesting tephric origin.The thinning pattern of L-units however, is occasionally interrupted by localised overthickening and indicates localised aeolian deposition during cool to cold climatic periods. The biostratigraphic record constructed from pollen examinations support the climatic interpretations made from the medial stratigraphy. The measurement of quartz content in medial units is shown to be a particularly useful parameter for assessing past climatic conditions. Two peaks in quartz influx were recorded and correlated to the full-glacial periods of oxygen isotope stages 2 and 4. Forming the North Taranaki coastal plain are five uplifted marine terraces, that provide a c.0.45 Ma record of successive sea level oscillations with moderate to low rates of crustal deformation. The present extent of these terraces is related to lahar deposits within their cover beds which have repeatedly advanced the coastline and retarded coastal erosion.
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    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.