The Taupo eruption, New Zealand I. General aspects

1985 ◽  
Vol 314 (1529) ◽  
pp. 199-228 ◽  
Keyword(s):  
New Zealand ◽  
Surface Water ◽  
Return Period ◽  
Eruption Column ◽  
Rapid Rate ◽  
Volcanic Centre ◽  
Circular Area ◽  
Ground Shaking ◽  
Eruption Volume ◽  
General Aspects

The ca . a.d. 186 Taupo eruption was the latest eruption at the Taupo Volcanic Centre, occurring from a vent, at Horomatangi Reefs, now submerged beneath Lake Taupo in the central North Island of New Zealand. Minor initial phreatomagmatic activity was followed by the dry vent 6 km 3 Hatepe plinian outburst. Large amounts of water then entered the vent during the 2.5 km 3 Hatepe phreatoplinian ash phase, eventually stopping the eruption, though large amounts of water continued to be ejected from the vent area, causing gullying of the ash deposits. After a break of several hours to weeks, phreatoplinian activity resumed, generating the 1.3 km 3 Rotongaio ash, notable for its fine grainsize and for containing significant quantities of non- or poorly-vesicular juvenile material. The vent area then became dry again, and eruption rates and power markedly increased into the 23 km 3 Taupo ‘ ultraplinian ’ phase, which is the most powerful plinian outburst yet documented. Synchronous with this ultraplinian activity, lesser volumes of non- to partially-welded ignimbrite were generated by diversion of ejecta from, or partial collapse of, the eruption column. The rapid rate of magma withdraw al during this phase removed support from the vent area, to trigger local vent collapse and initiate the catastrophic eruption of the ca. 30 km 3 Taupo ignimbrite. Finally, after some years, lava was extruded on to the floor of the reformed Lake Taupo, and floating fragments derived from the lava carapace were driven ashore. The known eruption volume is more than 65 km 3 , while additional volumes are represented by primary material now beneath Lake Taupo and layer 3 to the ignim brite phases; a total volume of more than 105 km 3 is likely, equivalent to more than 35 km 3 of magma plus more than 3 km 3 of lithic debris. Airfall deposits more than 10 cm thick blanketed 30000 km 2 of land east of the vent, while ignimbrite covers a near-circular area of 20000 km 2 . Widespread and locally severe ground shaking occurred during, but mostly after the eruption, associated with subsidence in the Lake Taupo basin. Secondary deposits are abundant above and extending beyond the Taupo ignimbrite, consisting of the products of surface water interacting with the still-hot ignimbrite and subsequent water reworking of the light, pumiceous materials. The complexity and size of this eruption preclude accurate forecasting of the size, nature and return period of the inevitable next eruption from the Taupo Volcanic Centre.

scholarly journals TephraNZ: a major and trace element reference dataset for prominent Quaternary rhyolitic tephras in New Zealand and implications for correlation

2020 ◽  
Author(s):  
Jenni L. Hopkins ◽  
Janine E. Bidmead ◽  
David J. Lowe ◽  
Richard J. Wysoczanski ◽  
Bradley J. Pillans ◽  
...  
Keyword(s):  
New Zealand ◽  
Trace Element ◽  
Major Element ◽  
Chemical Compositions ◽  
Volcanic Centre ◽  
Reference Dataset ◽  
Future Studies ◽  
Glass Shard ◽  
Tephra Deposits ◽  
Glass Shards

Abstract. Although analyses of tephra-derived glass shards have been undertaken in New Zealand for nearly four decades (pioneered by Paul Froggatt), our study is the first to systematically develop a formal, comprehensive, open access, reference dataset of glass-shard compositions for New Zealand tephras. These data will provide an important reference tool for future studies to identify and correlate tephra deposits and for associated petrological and magma-related studies within New Zealand and beyond. Here we present the foundation dataset for TephraNZ, an open access reference dataset for selected tephra deposits in New Zealand. Prominent, rhyolitic, tephra deposits from the Quaternary were identified, with sample collection targeting original type sites or reference locations where the tephra's identification is unequivocally known based on independent dating or mineralogical techniques. Glass shards were extracted from the tephra deposits and major and trace element geochemical compositions were determined. We discuss in detail the data reduction process used to obtain the results and propose that future studies follow a similar protocol in order to gain comparable data. The dataset contains analyses of twenty-three proximal and twenty-seven distal tephra samples characterising 45 eruptive episodes ranging from Kaharoa (636 ± 12 cal. yrs BP) to the Hikuroa Pumice member (2.0 ± 0.6 Ma) from six or more caldera sources, most from the central Taupō Volcanic Zone. We report 1385 major element analyses obtained by electron microprobe (EMPA), and 590 trace element analyses obtained by laser ablation (LA)-ICP-MS, on individual glass shards. Using PCA, Euclidean similarity coefficients, and geochemical investigation, we show that chemical compositions of glass shards from individual eruptions are commonly distinguished by major elements, especially CaO, TiO2, K2O, FeOt (Na2O+ K2O and SiO2/K2O), but not always. For those tephras with similar glass major-element signatures, some can be distinguished using trace elements (e.g. HFSEs: Zr, Hf, Nb; LILE: Ba, Rb; REE: Eu, Tm, Dy, Y, Tb, Gd, Er, Ho, Yb, Sm), and trace element ratios (e.g. LILE / HFSE: Ba / Th, Ba / Zr, Rb / Zr; HFSE / HREE: Zr / Y, Zr / Yb, Hf / Y; LREE / HREE: La / Yb, Ce / Yb). Geochemistry alone cannot be used to distinguish between glass shards from the following tephra groups: Taupō (Unit Y in the post-Ōruanui eruption sequence of Taupō volcano) and Waimihia (Unit S); Poronui (Unit C) and Karapiti (Unit B); Rotorua and Rerewhakaaitu; and Kawakawa/Ōruanui, Okaia, and Unit L (of the Mangaone subgroup eruption sequence). Other characteristics can be used to separate and distinguish all of these otherwise-similar eruptives except Poronui and Karapiti. Bimodality caused by K2O variability is newly identified in Poihipi and Tahuna tephras. Using glass shard compositions, tephra sourced from Taupō Volcanic Centre (TVC) and Mangakino Volcanic Centre (MgVC) can be separated using bivariate plots of SiO2/K2O vs. Na2O+K2O. Glass shards from tephras derived from Kapenga Volcanic Centre, Rotorua Volcanic Centre, and Whakamaru Volcanic Centre have similar major- and trace-element chemical compositions to those from the MgVC, but can overlap with glass analyses from tephras from Taupō and Okataina volcanic centres. Specific trace elements and trace element ratios have lower variability than the heterogeneous major element and bimodal signatures, making them easier to geochemically fingerprint.

scholarly journals Empirical models for predicting lateral spreading and evaluation using New Zealand data

2008 ◽  
Vol 41 (1) ◽  
pp. 10-23 ◽  
Author(s):  
Jian Zhang ◽  
Dick Beetham ◽  
Grant Dellow ◽  
John X. Zhao ◽  
Graeme H. McVerry
Keyword(s):  
New Zealand ◽  
Strong Motion ◽  
Lateral Spreading ◽  
Attenuation Relations ◽  
Geotechnical Parameters ◽  
Ground Shaking ◽  
Aerial Photos ◽  
New Model ◽  
The Difference ◽  
Lateral Displacements

A New empirical model has been developed for predicting liquefaction-induced lateral spreading displacement and is a function of response spectral displacements and geotechnical parameters. Different from the earlier model of Zhang and Zhao (2005), the application of which was limited to Japan and California, the new model can potentially be applied anywhere if ground shaking can be estimated (by using local strong-motion attenuation relations). The new model is applied in New Zealand where the response spectral displacement is estimated using New Zealand strong-motion attenuation relations (McVerry et al. 2006). The accuracy of the new model is evaluated by comparing predicted lateral displacements with those which have been measured from aerial photos or the width of ground cracks at the Landing Road bridge, the James Street loop, the Whakatane Pony Club and the Edgecumbe road and rail bridges sites after the 1987 Edgecumbe earthquake. Results show that most predicted errors (defined as the ratio of the difference between the measured and predicted lateral displacements to the measured one) from the new model are less than 40%. When compared with earlier models (Youd et al. 2002, Zhang and Zhao 2005), the new model provides the lowest mean errors.

A comparative study of the morphology, chemical composition and weathering of rhyolitic and andesitic glass

Clay Minerals ◽  
1980 ◽  
Vol 15 (2) ◽  
pp. 165-173 ◽  
Author(s):  
J. H. Kirkman ◽  
W. J. McHardy
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
New Zealand ◽  
Chemical Composition ◽  
Electron Probe ◽  
Volcanic Glass ◽  
Chemical Activity ◽  
Rapid Rate ◽  
Bonding Characteristics ◽  
Scanning Electron

AbstractThe morphology of volcanic glass particles in rhyolitic and andesitic tephra of central North Island and Taranaki areas of New Zealand has been studied by scanning electron microscopy. Electron probe analyses of the glasses are compared with those of the clays to which they weather. Loss of silica characterizes the weathering of both glasses. The rapid rate of weathering of andesitic glass is attributed to its occurrence as fine, soft microlites and extensive substitution of Al for Si in the structure. Rhyolitic glass weathers more slowly because it occurs as hard and brittle particles containing relatively little alumina. It is suggested that the structure, chemical composition and chemical activity of allophane is governed largely by the chemical composition and bonding characteristics of the parent glass.

The New Zealand grass Simplicia: biogeography, ecology and tectonics

2018 ◽  
Vol 31 (4) ◽  
pp. 281
Author(s):  
Michael Heads
Keyword(s):  
New Zealand ◽  
Natural Selection ◽  
Fault Zones ◽  
Eastern Province ◽  
Random Mutation ◽  
North West ◽  
Western Province ◽  
Alpine Fault ◽  
General Aspects ◽  
Tectonic Boundary

This paper analyses biogeography and ecology in the grass Simplicia, endemic to New Zealand, with respect to tectonic geology and to distributions in other groups of plants and animals. There are disjunctions and phylogenetic breaks at the Oparara basin (north-west Nelson), the Western Province–Eastern Province tectonic boundary, the Alpine fault and the Waihemo fault zone (Otago). Distribution boundaries at these localities recur in many other taxa and coincide spatially with important fault zones. General aspects of distribution and evolution in Simplicia are addressed, using a set of critical questions posed by McGlone (2015) as a conceptual framework. The biogeographic evidence suggests that the divergence of Simplicia and of its species took place by vicariance, and that this was mediated by tectonics. All individual plants of Simplicia have dispersed to their present locality, but there is no evidence that chance dispersal with founder speciation has occurred in the genus. Trends in these grasses, such as spikelet reduction, are global and have evolved in many different environments over tens of millions of years. This suggests that non-random mutation has been more important than environment and natural selection in directing the course of evolution.

Stable isotopic signatures of authigenic minerals in a Holocene ophiolitic debris flow, Southland, New Zealand

Clay Minerals ◽  
1995 ◽  
Vol 30 (2) ◽  
pp. 165-172 ◽  
Author(s):  
D. Craw ◽  
P. Blattner ◽  
C. A. Landis
Keyword(s):  
New Zealand ◽  
Surface Water ◽  
Debris Flow ◽  
Carbon Isotope ◽  
Climatological Data ◽  
Carbon Isotope Ratios ◽  
Isotopic Signatures ◽  
Mineral Growth ◽  
Stable Isotopic ◽  
O 24

AbstractAuthigenic chrysotile, stevensite, calcite, aragonite and pectolite have formed together in a Holocene ophiolitic debris flow in Southland, New Zealand. Mineral growth occurred about 4700-5700 years ago. The temperature of formation of these minerals is estimated from climatological data to be 5–10°C Surface water and groundwater δ180 is currently about –10‰, and was estimated to be about –9.5±1‰ during mineralization. Coexisting calcite (δ180 = +23‰) and aragonite (δl8O = +24‰) were in equilibrium with each other and with the groundwater at 5–10°C Stevensite δ180 is +14 to +16‰, chrysotile has δ180 = +5.5‰, and authigenic pectolite has δ180 near +10‰. Carbon isotope ratios for calcite and aragonite are strongly depleted (δ13C = –13 to –18) which suggests that dissolved CO2 had δ13C below -27. This isotopically light carbon probably resulted from a high organic component of carbon dissolved in the groundwater.

Estimating co-seismic subsidence in the Hutt Valley resulting from rupture of the Wellington Fault, New Zealand

2016 ◽  
Vol 49 (3) ◽  
pp. 283-291
Author(s):  
Dougal B. Townsend ◽  
John G. Begg ◽  
Russ J. Van Dissen ◽  
David A. Rhoades ◽  
Wendy S. A. Saunders ◽  
...  
Keyword(s):  
New Zealand ◽  
Sea Level ◽  
Ground Deformation ◽  
Mitigation Strategies ◽  
Societal Implications ◽  
Vertical Deformation ◽  
Ground Shaking ◽  
Mean Values ◽  
Permanent Ground Deformation ◽  
Strong Ground

Ground deformation can contribute significantly to losses in major earthquakes. Areas that suffer permanent ground deformation in addition to strong ground shaking typically sustain greater levels of damage and loss than areas suffering strong ground-shaking alone. The lower Hutt Valley of the Wellington region, New Zealand, is adjacent to the active Wellington Fault. The long-term signal of vertical deformation there is subsidence, and the most likely driver of this is rupture of the Wellington Fault. In 1855 the Mw ~8.2 Wairarapa Earthquake resulted in uplift of the lower Hutt Valley area and created an expectation that future earthquakes would do the same. However, sediments beneath the lower Hutt Valley floor up to c. 220 thousand years old provide data that when combined with the international sea level curve demonstrate cumulative net subsidence of up to c. 155 m during that period. Recent refinement of rupture parameters for the Wellington Fault (and other faults in the region), based on new field data, has spurred us to reassess estimates of vertical deformation in the Hutt Valley that would result from rupture of the Wellington Fault. Using a logic tree framework, we calculate subsidence for an “average” Wellington Fault event of ~1.9 m near Petone, ~1.7m near Lower Hutt City, ~1.4 m near Seaview, and ~0 m in the Taita area. Such a distribution of vertical deformation would result in large areas of Alicetown-Petone and Moera-Seaview subsiding below sea level. We also calculate and present “minimum” and “maximum” credible subsidence values, which are approximately half and twice the mean values, respectively. This ground deformation hazard certainly has societal implications, and we are working with local and regional councils to develop a range of mitigation strategies.

Development of New Zealand seismic bridge standards

2013 ◽  
Vol 46 (4) ◽  
pp. 201-221 ◽  
Author(s):  
L. S. Hogan ◽  
L. M. Wotherspoon ◽  
J. M. Ingham
Keyword(s):  
New Zealand ◽  
Lateral Spreading ◽  
Base Shear ◽  
Design Standards ◽  
Foundation Design ◽  
Ground Shaking ◽  
Lower Base ◽  
Current Design ◽  
Shear Demand ◽  
Structural Detailing

During seismic assessments of bridges where there is a lack of construction documentation, one method of determining likely structural detailing is to use historic design standards. An overview of the New Zealand bridge seismic standards and the agencies that have historically controlled bridge design and construction is presented. Standards are grouped into design era based upon similar design and loading characteristics. Major changes in base shear demand, ductility, foundation design, and linkage systems are discussed for each design era, and loadings and detailing requirements from different eras were compared to current design practices. Bridges constructed using early seismic standards were designed to a significantly lower base shear than is currently used but the majority of these bridges are unlikely to collapse due to their geometry and a preference for monolithic construction. Bridges constructed after the late 1970s are expected to perform well if subjected to ground shaking, but unless bridges were constructed recently their performance when subjected to liquefaction and liquefaction-induced lateral spreading is expected to be poor.

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