Extracting a primary Holocene crytoptephra record from Pupuke maar sediments, Auckland, New Zealand

Zawalna-Geer, Aleksandra; Lindsay, Jan M.; Davies, Siwan M.; Augustinus, Paul; Davies, Sarah J.

doi:10.1002/jqs.2866

Cited by 20 publications

(28 citation statements)

References 64 publications

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“…yr BP, but as a cryptotephra deposit of the same age in P08-06 (54 cm depth) (Shane et al, 2013). Similarly, Gehrels (2009), Shane et al (2013) and Zawalna-Geer et al (2016) showed that the preciselydated Kaharoa tephra (636  12 cal. yr BP) could be detected as a cryptotephra layer in Pupuke cores, thereby offering prospect for further resolving the timing of humanenvironmental impacts in Auckland region prehistory.…”

Section: Lake Pupukementioning

confidence: 87%

Two-step human–environmental impact history for northern New Zealand linked to late-Holocene climate change

et al. 2018

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Following resolution of a long-standing debate over the timing of the initial settlement of New Zealand from Polynesia (late 13 th century), a prevailing paradigm has developed that invokes rapid transformation of the landscape, principally by fire, within a few decades of the first arrivals. This model has been constructed from evidence mostly from southern and eastern regions of New Zealand, but a more complicated pattern may apply in the more humid western and northern regions where forests are more resilient to burning. We present a new pollen record from Lake Pupuke, Auckland, northern New Zealand, that charts the changing vegetation cover over the last 1000 years, before and after the arrival of people. Previous results from this site concurred with the rapid transformation model, although sampling resolution, chronology and sediment disturbance make that interpretation equivocal. Our new record is dated principally by tephrochronology together with radiocarbon dating, and includes a cryptotephra deposit identified as Kaharoa tephra, a key marker for first settlement in northern New Zealand. Its discovery and stratigraphic position below two Rangitoto-derived tephras enables a clearer picture of environmental change to be drawn. The new pollen record shows an early phase (step 1) of minor, localised forest clearance around the time of Kaharoa tephra (c. 1314 AD) followed by a later, more extensive deforestation phase (step 2) commencing at around the time of deposition of the Rangitoto tephras (c. 1400-1450 AD). This pattern, which needs to be corroborated from other well-resolved records from northern New Zealand, concurs with an emerging hypothesis that the 'Little Ice Age' had a significant impact on pre-European Māori with the onset of harsher conditions causing a consolidation of populations and later environmental impact in northern New Zealand.

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Section: Lake Pupukementioning

confidence: 87%

Two-step human–environmental impact history for northern New Zealand linked to late-Holocene climate change

et al. 2018

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“…Assessments of tephra fall hazard are typically carried out on a volcano-by-volcano basis, rather than for a given location. However, there is geological evidence for tephra falls from at least nine different volcanoes in the Chubu and Kanto regions close to Tokyo, Japan (Machida and Arai, 2003), and from more than five different volcanoes in Auckland, New Zealand (Shane and Hoverd, 2002;Zawalna-Geer et al, 2016). A key focus of this work is therefore to account for regional variation in the compounded site-specific tephra fall hazard and risk from multiple volcanoes.…”

Section: Introductionmentioning

confidence: 99%

Evaluating relative tephra fall hazard and risk in the Asia-Pacific region

Jenkins

Magill

Blong³

2018

Geosphere

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With increasing population densities and expanding urban boundaries, the potential for explosive volcanic eruptions to have adverse impacts upon urban areas is on the rise. This is particularly true for volcanoes along subduction zones, because they are almost exclusively explosive and often coincident with large populations. Explosive eruption hazards such as tephra fall have the potential to affect very large areas and numbers of people; populations in volcanic areas may therefore be exposed to tephra falls from more than one volcano. In this study we have simulated large numbers of plausible explosive eruptions of Volcanic Explosivity Index (VEI) 4 or greater for each of 141 volcanoes in the Asia-Pacific region. Tephra fall footprints are aggregated for 16 major cities, according to their probability of occurrence. This addresses an emerging need for international agencies and organizations to conduct regional-scale assessments, where at-risk areas can be compared on a like-for-like basis. Hazard in cities near subduction zones is two to three orders of magnitude greater than for those farther away. By combining our hazard estimates with indicators describing the exposure and vulnerability of people and infrastructure, tephra fall risk scores were calculated for each city. Risk is evaluated separately for human populations and potential economic impact, with the highest human risk scores calculated for Manila and the highest economic scores for Tokyo. The volcanoes with the greatest hazard contribution in the very populous cities of Manila, Tokyo, and Jakarta were identified as Taal (Manila), Fujisan (Tokyo), and six volcanoes equally (Jakarta). While this study provides a transparent and consistent method for assessing regional volcanic hazard and risk, there are challenges associated with the data-poor setting and we conclude by discussing what is required in order to improve regional tephra fall hazard and risk assessments. This study provides a regional-scale assessment that cannot replace hazard and risk information provided locally by official organizations.

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“…However, records of thin ashfall layers from several Holocene Taupo eruptions are preserved in cores from lakes or bogs throughout the North Island, suggesting that they had much wider coverage than implied by published isopach maps (e.g., Eden et al, 1993;Froggatt & Rogers, 1990;Howorth et al, 1980;Hubbard & Neall, 1980;de Lange & Lowe, 1990;Lowe, 1988aLowe, , 1988bLowe et al, 1999Lowe et al, , 2013Pullar et al, 1977: supporting information Figure S19). For example, tephra from the 232 AD Taupo eruption is preserved as far north as Auckland at thicknesses of up to 10 mm (Gehrels et al, 2006;Zawalna-Geer et al, 2016). In addition, up to five other Taupo-derived tephras are found in Hamilton lakes and bogs and several cryptotephras have been inferred from Auckland lake cores (Lowe et al, 2008;Zawalna-Geer et al, 2016).…”

Section: Comparisons With the Geological Recordmentioning

confidence: 99%

Modeling Ash Dispersal From Future Eruptions of Taupo Supervolcano

Barker

Eaton

Mastin

et al. 2019

Geochem Geophys Geosyst

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Hazard analysis at caldera volcanoes is challenging due to the wide range of eruptive and environmental conditions that can plausibly occur during renewed activity. Taupo volcano, New Zealand, is a frequently active and productive rhyolitic caldera volcano that has hosted the world's youngest known supereruption and numerous smaller explosive events. To assess ashfall hazard from future eruptions, we have simulated atmospheric ash dispersal using the Ash3d model. We consider five eruption scenarios spanning magma volumes of 0.1–500 km3 and investigate the main factors governing ash dispersal in modern atmospheric conditions. Our results are examined in the context of regional synoptic weather patterns (Kidson types) that provide a framework for assessing the variability of ashfall distribution in different wind fields. For the smallest eruptions (~0.1‐km3 magma), ashfall thicknesses >1 cm are largely confined to the central North Island, with dispersal controlled by day‐to‐day weather and the dominance of westerly winds. With increasing eruptive volume (1–5‐km3 magma), ashfall thicknesses >1 cm would likely reach major population centers throughout the North Island. Dispersal is less dependent on weather patterns as the formation of a radially expanding umbrella cloud forces ash upwind or crosswind, although strong stratospheric winds significantly restrict umbrella spreading. For large eruptions (50–500‐km3 magma), powerful expansion of the umbrella cloud results in widespread ashfall at damaging thicknesses (>10 cm) across most of the North Island and top of the South Island. Synoptic climatology may prove a useful additional technique for long‐term hazard planning at caldera volcanoes.

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Extracting a primary Holocene crytoptephra record from Pupuke maar sediments, Auckland, New Zealand

Cited by 20 publications

References 64 publications

Two-step human–environmental impact history for northern New Zealand linked to late-Holocene climate change

Two-step human–environmental impact history for northern New Zealand linked to late-Holocene climate change

Evaluating relative tephra fall hazard and risk in the Asia-Pacific region

Modeling Ash Dispersal From Future Eruptions of Taupo Supervolcano

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