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Item Agriculture and forestry impact assessment for tephra fall hazard: fragility function development and New Zealand scenario application(Volcanica, 2021-12-31) Craig HM; Wilson TM; Magill C; Stewart C; Wild AJDeveloping approaches to assess the impact of tephra fall on agricultural and forestry systems is essential for informing effective disaster risk management strategies. Fragility functions are commonly used as the vulnerability model within a loss assessment framework and represent the relationship between a given hazard intensity measure (HIM; e.g. tephra thickness) and the probability of impacts occurring. Impacts are represented using an impact state (IS), which categorises qualitative and quantitative statements into a numeric scale. This study presents IS schemes for pastoral, horticultural, and forestry systems, and a suite of fragility functions estimating the probability of each IS occurring for 13 sub-sectors. Temporal vulnerability is accounted for by a ‘temporality/seasonality coefficient,’ and a ‘fluoride toxicity coefficient’ is included to incorporate the increased vulnerability of pastoral farms when tephra is high in leachable fluoride. The fragility functions are then used to demonstrate a deterministic impact assessment with current New Zealand exposure.Item Late quaternary volcanic stratigraphy of the southeastern sector of the Mount Ruapehu ring plain New Zealand : a thesis presented as partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science(Massey University, 1991) Donoghue, Susan LeighMt Ruapehu is an active composite strato-volcano situated within the Tongariro Volcanic Centre, North Island, New Zealand. It is surrounded by an extensive ring plain built principally from laharic deposits, capped by late Pleistocene and Holocene-aged tephras. Stratigraphic studies and geologic mapping on the southeastern sector of the Mt Ruapehu ring plain have identified six andesitic tephra formations (Tufa Trig Formation, Ngauruhoe Formation, Mangatawai Tephra, Mangamate Tephra, Pahoka Tephra, Bullot Formation) erupted from Mt Ruapehu, Mt Tongariro and Mt Ngauruhoe during the past c. 22 500 years. A seventh formation, Papakai Formation, comprises both andesitic tephra and tephric loess. Most of the tephras erupted from Mt Ruapehu are grouped into the Bullot and Tufa Trig formations which are of late Pleistocene to Holocene age. Other intermittent eruptions during the Holocene have contributed tephra to the Papakai Formation. The Bullot Formation tephras represent a period of active and widespread tephra deposition from subplinian eruptions. Most of the tephras have been deposited to the east of the volcano under the influence of prevailing westerly winds, with an average eruption interval of approximately one event every 200 years. Tephras of Tufa Trig Formation are the products of small hydrovolcanic eruptions and, although erupted more frequently (one event approximately every 100 years), have contributed comparatively little tephra to the ring plain. Tephras erupted from Mt Tongariro (Mangamate Tephra, Pahoka Tephra) comprise most of the Holocene tephra record on the Mt Ruapehu ring plain, being deposited during a period of quiescence at Mt Ruapehu. Their eruption is coincident with the introduction of mixed magmas beneath Mt Tongariro. Fourteen rhyolitic tephra formations (Kaharoa Tephra, Mapara Tephra, Taupo Pumice, Waimihia Tephra, Hinemaiaia Tephra, Whakatane Tephra, Motutere Tephra, Poronui Tephra, Karapiti Tephra, Waiohau Tephra, ?Rotorua Tephra, Rerewhakaaitu Tephra, Okareka Tephra, Kawakawa Tephra Formation) erupted from the Okataina and Taupo volcanic centres of the central North Island have also been identified. They are important marker beds used to date andesitic tephras and laharic deposits preserved on the southeastern ring plain. The stratigraphic relationships between these distal rhyolitic tephras, and their relationship to local andesitic tephras is discussed, and the stratigraphy of some rhyolitic tephras identified by Topping and Kohn (1973) revised. The tephras have been identified from their stratigraphic positions, ferromagnesian mineral assemblages and glass shard chemistries. The mineralogy and chemistry of selected andesitic marker beds has been detailed for purposes of regional identification and correlation. A database for Tongariro Centre tephras is established using ferromagnesian mineral assemblages and major element chemistry of ferromagnesian phenocrysts, and glass determined by electron microprobe analysis. The potential for use of andesitic tephra mineralogy in stratigraphic studies is evaluated. The ferromagnesian mineral assemblage of Tongariro Volcanic Centre tephras comprises orthopyroxene + clinopyroxene ± olivine ± hornblende. Orthopyroxene compositions project mostly as hypersthene, and clinopyroxenes as augite. Olivine and hornblende are valuable marker minerals to the identification of some tephras. The olivines are forsteritic, some of which show distinctive skeletal morphology. The hornblende phenocrysts are calcic amphiboles and project mostly as pargasitic hornblende. Groundmass glass compositions of some pumice lapilli range between andesite and rhyolite. Bulk rock compositions are andesite. The deposits of debris flows and hyperconcentrated flood flows comprise much of the prehistoric stratigraphy of the southeastern Ruapehu ring plain, with minor fluvial lithologies, indicating lahars are common events at Mt Ruapehu. The deposits are grouped into five formations (Onetapu Formation, Manutahi Formation, Mangaio Formation, Tangatu Formation, Te Heuheu Formation) on the basis of lithology. The stratigraphic relationships between these formations is discussed and their distributions mapped. These formations form the major constructional surfaces of the southeastern ring plain. They are envisaged as having been generated following large scale sector collapses of the southeastern flanks of Mt Ruapehu, and by snow and ice melt associated with eruption of hot pyroclastic ejecta, the ejection of Crater Lake waters, or by heavy rains inducing widespread flood events, capable of eroding flank and ring plain materials. Much of the erosion and aggradation that has occurred within the Rangipo Desert in the last c. 1800 years is attributable to lahars. At least 35 laharic events are recorded on the southeastern ring plain within the last c. 22 500 years. The most active period of lahar generation is the present day, with an average incidence of one event every 11 years. Many of the recent lahars have been confined within Whangaehu Valley.Item Late quarternary volcanic stratigraphy within a portion of the northeastern Tongariro volcanic centre : a thesis presented as partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science(Massey University, 1996) Cronin, Shane JasonInvestigation of the Late Quaternary volcanic stratigraphy within the andesitic Tongariro Volcanic Centre has elucidated the history of construction of the northeastern Ruapehu and eastern Tongariro ring plains and provided a lahar record for the Tongariro catchment. Volcaniclastic ring-plain sequences were correlated and dated using rhyolitic and andesitic marker tephras. The identification of distal rhyolitic tephras in the area was improved by the application of discriminant function analysis (DFA) to their electron microprobe-determined glass chemistry. The Okaia. Omataroa and Hauparu Tephras and the Rotoehu Ash were identified for the first time in this area, providing a chronology for pre-22.6 ka ring-plain sequences not previously investigated. DFA of ferromagnesian mineral chemistry proved useful for discrimination of andesitic tephras. with titanomagnetite being the most useful phase. Development of an andesitic tephrostratigraphy in pre-22.6 ka sequences was aided by clustering analysis and DFA. Seven andesitic marker tephras were identified using a range of parameters to supplement the rhyolitic tephrostratigraphy. Using the tephrochronologic framework, 15 packages of lahar deposits were identified on the northeastern Ruapehu ring plain (from >64 to c. 5.2 ka) and six on the eastern Tongariro ring plain (from >22.6 to 11.9 ka). Lahar deposition on both ring plains was most voluminous and widespread during the last (Ohakean) and antepenultimate (Porewan) stadials of the last glacial (Otiran). Holocene lahars were restricted to a narrow sector of the northeastern Ruapehu ring plain. They appear to have been triggered mostly in response to large-scale tephra eruptions of Ruapehu and Tongariro, and mostly occurred along the path of the Mangatoetoenui Stream. Lahar deposits and surfaces beside the Tongariro River were mapped in eight lahar hazard zones, with lahar recurrence intervals ranging from 1 in >15 000 years to 1 in 35 years. The largest number and volume of lahars in this catchment occurred in the period from 14.7 to 10 ka. The greatest population risk identified in the Tongariro catchment is part of Turangi, built within a 1 in 1000 year lahar-hazard zone. Other property and infrastructure at greater risk include the State Highway 1 bridge across the Mangatoetoenui Stream and the Rangipo Dam and Power Station, within a 1 in 35 year hazard zone. The landscape of the northeastern Ruapehu and eastern Tongariro ring plains has developed in relation to late Quaternary climate changes in addition to volcanic activity. During the last and antepenultimate stadials of the last glacial, major ring-plain aggradation by lahars and streams occurred. This was probably in response to greater physical weathering and glacier action on the volcanic cones providing abundant sediment for lahars. During the warmer interstadials of the last glacial, soil development within andesitic ring plain material was greatest, particularly when the rate of soil accretion was low.Item 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 VictorThis 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.Item Andesitic Plinian eruptions at Mt. Ruapehu (New Zealand) : from lithofacies to eruption dynamics : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Earth Science at Massey University, (Palmerston North, Manawatu), New Zealand(Massey University, 2012) Pardo Villaveces, NataliaA new detailed stratigraphy was developed for a sequence of pyroclastic deposits including the largest known eruptions associated with Mt. Ruapehu, deposited in the period ~27-10 ka BP cal. From the largest Plinian eruption deposits in this sequence, subtle lithofacies variations within componentry, pumice textures and sedimentary features were used to identify a systematic change in eruptive conditions over time. Early eruptions involved steady eruption columns, while younger eruptions involved unsteady, collapsing columns. Isopach and Isopleth (pumice and lithic) mapping of most widespread and distinctive units show that the largest explosive eruptions known from this volcano attained peak column heights between 22 and 37 km, with mass discharge rates reaching 107-108 kg/s. To characterise the conditions controlling the style of Plinian eruptions at this andesitic volcano, and to explain the systematic variation in column stability over time, five key units were sampled in detail, exemplifying the major contrasting lithofacies. The sampled tephras underwent grain-size analysis, along with quantification of componentry, porosimetry and density on particles of a range of size classes, as well as 2D and 3D microtextural analyses of juvenile pumice clasts to define vesicularity and crystallinity. In addition, physiochemical factors such as melt-evolution and volatile-contents were determined by analysing bulk pumice, glass-inclusions and residual glasses with electron microprobe and FTIRspectroscopy. Bulk compositions of these tephras vary from basaltic-andesite to andesite (56-62 wt.%, SiO2), and had minimum pre-eruptive H2O contents of 4-5 wt.%. The evolution of eruption behaviour over time was not correlated to any progressive change in bulk geochemical properties, but instead resulted from variations in physical processes within the conduit. Ascending magmas experienced heterogeneous bubble nucleation, and later-erupted units showed increasing degrees of rheological heterogeneities developed across the conduit. Differences between units were due to changes in the magma decompression rates, the degree of bubble-crystal-melt interactions and bubble shearing, as well as the composition of the residual melt. Conditions that led to the most variable physical states of the magma reaching the fragmentation level resulted in the highest variability in pumice textures, the greatest range in styles of fragmentation, and the most unstable eruption columns. A new model describing the pre-eruptive magma storage region, conduit processes, magma fragmentation, and pyroclastic dispersal during Plinian eruptions at Mt. Ruapehu is proposed. This hypothesises that eruption column unsteadiness and collapse occurs when magma shear reaches extreme levels along the conduit under conditions of low isolated porosity (<3 vol.%). This situation also generates the worst-case hazard scenarios expected for Ruapehu, eruptions, where Plinian columns of over 30 km may produce widespread tephra fall, as well as partially collapse to generate pyroclastic density currents of over 15 km runout.Item Soils of Eltham county and the tephrochronology of central Taranaki : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science(Massey University, 1984) Franks, Alison MargaretThe soils of Eltham County west of the Patea River, are described and their distribution shown on a map at a scale of 1:50,000. The soil-forming factors are discussed with particular emphasis on the soil parent materials, which range from volcanic ash in the west, to peat and sedimentary rock, mainly siltstone and sandstone, in the east. An account is given of the genesis and historical development of the Ngaere and Eltham Swamps and a classification made of the Eltham peat. A detailed account is given of the stratigraphy of the late Quaternary tephras in central Taranaki. Eight new tephra units (p2, p1, E5, E4, E3, E2, E1 and Mahoe) are described, with type sections and reference localities designated. Isopach maps of their distribution are presented and an attempt is made to correlate these tephras with those further north. Details are given of the westernmost occurrences of Aokautere Ash and the implications of these for the Late Quaternary in Taranaki are examined. Petrographic studies, X-ray fluorescence and chemical analysis of titanomagnetites by inductively-coupled argon plasma emission spectroscopy (I.C.P.) are also applied to effect positive identification and correlation of the tephras. The composition of the lithic Manganui tephra is established as basaltic. The morphology and physical properties of the soils are described as are the soil mapping units employed in this survey. Characteristics of the component members of the mapping units are given in an extended legend. Fifteen soil taxonomic units have been recognised and named in the soil survey. Descriptions designed primarily for correlation and reference purposes are provided for each of the taxonomic units. The soils are also rated in terms of their limitations for pastoral cropping, horticultural, forestry and urban uses and in terms of their value for food production. The position of the boundary between Stratford and Egmont soils is established and a basis for distinguishing the two soils is proposed. By examining two steepland subcatchments in detail an insight is provided into the wide range of variability found in the steepland soils in the east of Eltham County. An indication of the presence of volcanic ash or its absence due to erosion is gained by applying the phosphate retention and allophane test. This also provides an understanding of the pattern of parental material variability. Finally, selected laboratory analyses have been chosen to help characterise the chemical and physical properties of five yellow-brown loams, a gley, an intergrade between yellow-brown loams and recent soils and an organic soil from Eltham County. Detailed analytical data from ten New Zealand Soil Bureau reference sites in Taranaki are included for comparative purposes.Item Origin of selected soil parent materials and sediments in North Island, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University(Massey University, 1982) Stewart, Robert BruceIn this thesis the origin of soil parent materials in the North Island of New Zealand was investigated. The parent materials varied from basaltic, andesitic and rhyolitic volcanics to quartzose beach sands and quartzofeldspathic sedimentary rocks. Oxygen isotope and grain size analysis show that quartz from global aerosolic dust (represented by the 5 - 2 µm size fraction), interregional loess (represented by the 63 - 20 µm size fraction) and intraregional sand (represented by the >63 µm size fractions) can be identified in soils formed from these materials. In addition, high temperature quartz from Central North Island rhyolitic tephras is identified in basaltic soils in Northland. The presence of locally derived quartz in the aerosolic dust fraction is demonstrated in the basaltic Kiripaka soil from Northland. In this soil a low temperature quartz component with a δ180 value of circa 26 °/00 (in contrast to the aerosolic quartz δ180 value of 12 - 13 °/00) was derived from nearby Tertiary marine shales by erosion and wind transport. In all of the soils examined, no evidence of pedogenic α-quartz was obtained. In particular, quartz from the highly siliceous albic horizon of a Wharekohe soil, a "kauri podzol", is of detrital rather than authigenic origin. Aerosolic quartz accumulation in soils developed on a series of surfaces of known age in southern North Island shows a correlation between age and the amount of quartz accumulated. Thus within a region, relative ages of surfaces can be estimated from quartz accumulation. In an Egmont soil from Taranaki, an increased rate of quartz accumulation is noted in the lower part of the soil profile. This is correlated with a late glacial climate prior to the circa 11,000 year B.P. post-glacial rise in sea-level. During this time tephric loess with a substantial (30%) detrital quartzofeldspathic component accumulated. After the sea-level rise cut off the source of the tephric loess, only tephra accumulated to form the upper part of the soil profile, in which the detrital quartzofeldspathic component is small. The chronosequence concept could not be directly applied to a development sequence of basaltic soils in Northland. Only one soil, the Kiripaka, accumulated fast enough for the glacial/post-glacial change in quartz accumulation to be detected. The remaining basaltic soils, Whatitiri, Waiotu, Kerikeri, Ruatangata and Okaihau, accumulated slowly on old surfaces and in some cases were subject to erosion. In a mineralogical examination of the sand and silt fractions of the basaltic soils, four distinct components are recognised: 1. Basaltic component - comprising minerals inherited from primary basalt tephra or lava. These include calcic plagioclase, magnetite, augite and, rarely, olivine. 2. Secondary component - glaebules of gibbsite, goethite and lesser amounts of clay minerals and hematite. 3. Rhyolitic component - abundant in the surface horizons of all six soils and comprising rhyolitic glass shards and pumice, sodic plagioclase, hypersthene, hornblende, augite, biotite, titanomagnetite, quartz, zircon and rare sanidine. 4. Detrital component - comprising predominantly quartz < 125 μm in size and largely derived as loess and aerosolic dust. Other minerals occurring are muscovite, plagioclase and rarely microcline and tourmaline. Through the soil development sequence the basaltic component rapidly becomes unimportant while the secondary component increases in significance to a level where the soil grain size characteristics are largely controlled by the distribution of gibbsite and goethite glaebules. In a further study of quartz accumulation with time, a core of marine sediment from off the east coast of the southern North Island is examined. Core P69 contains five tephras, Whakatane Ash, Rotoma Ash, Waiohau Ash and Kawakawa Tephra, which have been radiocarbon dated from terrestrial sequences. Interpolation and extrapolation of sedimentation rates in core P69 allowed estimates of the ages of four further rhyolitic tephras from the Central North Island, for which no reliable radiocarbon dates are available: Okareka Ash 17,100 years B.P. Te Rere Ash 19,100 years B.P. Poihipi Tephra 20,300 years B.P. Okaia Tephra 21,200 years B.P. Quartz accumulation decreases abruptly from a high Otiran (glacial) to a low Aranuian (post-glacial) rate at circa 14,700 years B.P. This is matched by a similar abrupt change in both biogenic silica and carbonate accumulation. The changes are interpreted as reflecting a southward shift of a strong westerly wind system at the end of the Otiran. The decreased wind intensity, coupled with forest expansion led to a reduction in erosion and reduced transport of quartz. The biological components also decreased at this time, probably due to changes in ocean currents and upwelling of cold, nutrient-rich water, as a result of the decreased wind intensity. Compared with aerosolic dust accumulation in the southern North Island chronosequence, far greater amounts of aerosolic quartz accumulated in core P69 over a similar time period. This indicates that local contributions to the 5 - 2 μm size fraction can cause much larger variations in quartz accumulation than those caused by rainfall variations reported in the literature. The following late Otiran - Aranuian chronology is suggested, based on the evidence in core P69: 23,000 - 19,200 cold, glacial 19,200 - 18,500 glacial, slight amelioration 18,500 - 16,200 glacial, maximum cold 16,200 - 14,700 climatic amelioration, maximum aeolian transport and erosion, little forest cover 14,700 - 14,400 southward migrating circumpolar currents and westerly wind systems leave area of core P69, rapid expansion of forest cover 14,400 - 9,500 ameliorating climate, early post-glacial 9,500 - present post-glacial.Item Magmaticand phreatomagmatic tephras in fine ash successions of an arc volcanic complex, the Mangatawai Tephra Formation, Tongariro Volcanic Centre, New Zealand(Massey University., 2007-01-01) Moebis, Anja; Cronin, Shane J.; Nemeth, KarolyNo abstract available