title: Silicic volcanism of the Tauranga Volcanic Centre and the climactic Waiteariki supereruption at the dawn of the Taupō Volcanic Zone

authors: Prentice, Marlena Lee

subjects: Volcanism

abstract: The Tauranga Volcanic Centre (TgaVC), located in the western Bay of Plenty, Aotearoa New Zealand was active between 2.9–1.9 Ma.  Silicic volcanism of this period occurred spatially and temporally between the defined locations of the Taupō Volcanic Zone (TVZ) and its predecessor, the Coromandel Volcanic Zone (CVZ), but despite their prominence, the volcanic origin, eruption dynamics and petrogenetic relationships of the volcanic deposits of this period have not previously been studied in detail.  This study combines a comprehensive field study with whole-rock, glass and mineral geochemistry and isotopic (Sr, Nd and O) analysis to interpret the origin, evolution and petrogenetic relations of the volcanic deposits of the TgaVC, with particular emphasis on the deposits of the Waiteariki Ignimbrite.   
This thesis provides an enhanced chronology for explosive volcanism of the TgaVC with four locally widespread units named and defined as follows: Welcome Bay and Wharo ignimbrites (together formerly known as Lower Pāpāmoa Ignimbrite); Otawera Ignimbrite; and Arateka Ignimbrite (formerly known as Upper Pāpāmoa Ignimbrite).  These eruptives were followed by the eruption of the voluminous (870 ± 87 km³ DRE) Waiteariki Ignimbrite at 2.1 Ma which has been correlated with the distal Hikuroa Pumice Member in northern Hawke’s Bay (150-170 km southeast of TgaVC).  The integrated proximal and distal records show that at least eight eruptions occurred in the TgaVC between 2.4 and 1.9 Ma and provide a maximum repose period between explosive eruptions of ca. 50 kyrs. 
The magnitude 8 (M8) Waiteariki super-eruption consisted of the eruption of crystal-rich rhyodacite magma from the newly defined Omanawa Caldera, identified here on the basis of ignimbrite thickness variations, textural features and the presence of numerous silicic lava domes in association with a prominent negative gravity anomaly situated at the southern end of an asymmetrical rifted graben underlying the northern Mamaku Plateau.  The Waiteariki Ignimbrite is a monotonous intermediate deposit, characterised by crystal-rich (37 %), rhyodacite (ave. 70.7 wt. % SiO₂) magma with a consistent mineralogical assemblage of plagioclase, hornblende, pyroxene, quartz ± biotite; restricted ranges in whole-rock geochemistry and matrix glass compositions; and the complete absence of compositional gradients and a precursory Plinian phase.  Phenocrysts, however, record a complex evolutionary history, providing evidence for a highly heterogeneous mush-source zone.
Individual lavas of the Minden Rhyolite Subgroup of the TgaVC can be grouped into either low- and high-⁸⁷Sr/⁸⁶Sr magmas exclusively erupted in the west and east, respectively.  Juvenile products within the Waiteariki and Welcome Bay ignimbrites are mineralogically, geochemically, and isotopically consistent with the high-⁸⁷Sr/⁸⁶Sr Minden Rhyolites, which connects these domes to the magmatic system underlying the Omanawa Caldera.  Nd and Sr isotopic values across the TgaVC are comparable to those of the broader TVZ.  Calculated δ¹⁸Oₘₑₗₜ values for the TgaVC magmas indicate a temporal trend of decreasing δ¹⁸Ovalues in the TVZ through time.  Upper crustal differentiation was dominated by fractional crystallisation (i.e western domes) or assimilation-fractional crystallisation followed by mixing of magmas (Omanawa magma body and eastern domes) while segregated melts (e.g. Bowentown, Mt Maunganui, Maungatūtū/Mt Misery) have unique late-stage differentiation histories.  
As volcanism associated with the Omanawa Caldera and the broader TgaVC occurred within the defined structural boundaries of the Taupō Rift, volcanism of the TgaVC is regarded here to represent the first silicic system of the TVZ.  Geothermobarometry indicate crystallisation and storage occurred within the mid- to shallow crust (c. 3.5 to 6 km depth) between 50-160 MPa and 740-900 °C indicating that magmas have broadly resided under near-identical, shallow conditions over the lifespan of the TVZ (~2.5 Ma).  Dominated by high-silica, crystal-poor rhyolitic magmas, the continued eruption of homogenous, crystal-rich magmas throughout the TgaVC is unique within the context of the TVZ and it is inferred that active crustal rifting enabled continual tapping of the crystal-mush reservoir which culminated in a deep-seated failure of the magma reservoir, followed by rapid decompression and large-scale evacuation of the Omanawa magmatic system.

text: Silicic volcanism of the Tauranga Volcanic Centre and the climactic Waiteariki supereruption at the dawn of the Taupō Volcanic Zone The Tauranga Volcanic Centre (TgaVC), located in the western Bay of Plenty, Aotearoa New Zealand was active between 2.9–1.9 Ma.  Silicic volcanism of this period occurred spatially and temporally between the defined locations of the Taupō Volcanic Zone (TVZ) and its predecessor, the Coromandel Volcanic Zone (CVZ), but despite their prominence, the volcanic origin, eruption dynamics and petrogenetic relationships of the volcanic deposits of this period have not previously been studied in detail.  This study combines a comprehensive field study with whole-rock, glass and mineral geochemistry and isotopic (Sr, Nd and O) analysis to interpret the origin, evolution and petrogenetic relations of the volcanic deposits of the TgaVC, with particular emphasis on the deposits of the Waiteariki Ignimbrite.   
This thesis provides an enhanced chronology for explosive volcanism of the TgaVC with four locally widespread units named and defined as follows: Welcome Bay and Wharo ignimbrites (together formerly known as Lower Pāpāmoa Ignimbrite); Otawera Ignimbrite; and Arateka Ignimbrite (formerly known as Upper Pāpāmoa Ignimbrite).  These eruptives were followed by the eruption of the voluminous (870 ± 87 km³ DRE) Waiteariki Ignimbrite at 2.1 Ma which has been correlated with the distal Hikuroa Pumice Member in northern Hawke’s Bay (150-170 km southeast of TgaVC).  The integrated proximal and distal records show that at least eight eruptions occurred in the TgaVC between 2.4 and 1.9 Ma and provide a maximum repose period between explosive eruptions of ca. 50 kyrs. 
The magnitude 8 (M8) Waiteariki super-eruption consisted of the eruption of crystal-rich rhyodacite magma from the newly defined Omanawa Caldera, identified here on the basis of ignimbrite thickness variations, textural features and the presence of numerous silicic lava domes in association with a prominent negative gravity anomaly situated at the southern end of an asymmetrical rifted graben underlying the northern Mamaku Plateau.  The Waiteariki Ignimbrite is a monotonous intermediate deposit, characterised by crystal-rich (37 %), rhyodacite (ave. 70.7 wt. % SiO₂) magma with a consistent mineralogical assemblage of plagioclase, hornblende, pyroxene, quartz ± biotite; restricted ranges in whole-rock geochemistry and matrix glass compositions; and the complete absence of compositional gradients and a precursory Plinian phase.  Phenocrysts, however, record a complex evolutionary history, providing evidence for a highly heterogeneous mush-source zone.
Individual lavas of the Minden Rhyolite Subgroup of the TgaVC can be grouped into either low- and high-⁸⁷Sr/⁸⁶Sr magmas exclusively erupted in the west and east, respectively.  Juvenile products within the Waiteariki and Welcome Bay ignimbrites are mineralogically, geochemically, and isotopically consistent with the high-⁸⁷Sr/⁸⁶Sr Minden Rhyolites, which connects these domes to the magmatic system underlying the Omanawa Caldera.  Nd and Sr isotopic values across the TgaVC are comparable to those of the broader TVZ.  Calculated δ¹⁸Oₘₑₗₜ values for the TgaVC magmas indicate a temporal trend of decreasing δ¹⁸Ovalues in the TVZ through time.  Upper crustal differentiation was dominated by fractional crystallisation (i.e western domes) or assimilation-fractional crystallisation followed by mixing of magmas (Omanawa magma body and eastern domes) while segregated melts (e.g. Bowentown, Mt Maunganui, Maungatūtū/Mt Misery) have unique late-stage differentiation histories.  
As volcanism associated with the Omanawa Caldera and the broader TgaVC occurred within the defined structural boundaries of the Taupō Rift, volcanism of the TgaVC is regarded here to represent the first silicic system of the TVZ.  Geothermobarometry indicate crystallisation and storage occurred within the mid- to shallow crust (c. 3.5 to 6 km depth) between 50-160 MPa and 740-900 °C indicating that magmas have broadly resided under near-identical, shallow conditions over the lifespan of the TVZ (~2.5 Ma).  Dominated by high-silica, crystal-poor rhyolitic magmas, the continued eruption of homogenous, crystal-rich magmas throughout the TgaVC is unique within the context of the TVZ and it is inferred that active crustal rifting enabled continual tapping of the crystal-mush reservoir which culminated in a deep-seated failure of the magma reservoir, followed by rapid decompression and large-scale evacuation of the Omanawa magmatic system.

year: 2023

title: Community understanding and preparedness for tsunami risk in the eastern North Island, New Zealand

authors: Pishief, Katharine Sophie

subjects: tsunami

abstract: The Indian Ocean tsunami on 26 December 2004 made many New Zealanders more aware of the devastating affects that a tsunami can have on coastal communities, and highlighted the need for people living in the coastal zone to be prepared for natural hazard events. The east coast of New Zealand is at high risk from both local and distantly generated tsunami, and Poverty Bay and Hawke Bay have been identified among the most at risk areas from tsunamis in the country. Three surveys were conducted between January and November 2006 to assess community understanding of, and preparedness for tsunami risk in the eastern North Island, New Zealand. These surveys were a camping ground visitor survey; a tourism sector preparedness survey; and the 2006 National Coastal Survey.
Findings of all three surveys show that the general public does not appear to have sufficient knowledge of tsunami risk in their area. Also, there does not appear to be adequate information on tsunamis available to the public. Understanding of official tsunami warnings was high amongst residents surveyed in the 2006 National Coastal Survey. However, it was low amongst visitors surveyed in the camping grounds, with the majority of camping ground survey respondents indicating that they do not know what makes up the New Zealand public notification system. It is encouraging to find that overall the public are aware of the correct actions to take in the event of a tsunami warning being issued.
Staff in hotels/motels in the Napier area were not well prepared for managing natural hazard events, with the majority of respondents having no training for dealing with emergencies, and none of those who had received training had received training for tsunami hazards.
It is recommended that steps be taken to better educate and prepare the public and tourism managers in eastern North Island communities. This will require not only public education but a range of activities that engage, empower and motivate at-risk communities to respond effectively and appropriately to tsunami warnings.

text: Community understanding and preparedness for tsunami risk in the eastern North Island, New Zealand The Indian Ocean tsunami on 26 December 2004 made many New Zealanders more aware of the devastating affects that a tsunami can have on coastal communities, and highlighted the need for people living in the coastal zone to be prepared for natural hazard events. The east coast of New Zealand is at high risk from both local and distantly generated tsunami, and Poverty Bay and Hawke Bay have been identified among the most at risk areas from tsunamis in the country. Three surveys were conducted between January and November 2006 to assess community understanding of, and preparedness for tsunami risk in the eastern North Island, New Zealand. These surveys were a camping ground visitor survey; a tourism sector preparedness survey; and the 2006 National Coastal Survey.
Findings of all three surveys show that the general public does not appear to have sufficient knowledge of tsunami risk in their area. Also, there does not appear to be adequate information on tsunamis available to the public. Understanding of official tsunami warnings was high amongst residents surveyed in the 2006 National Coastal Survey. However, it was low amongst visitors surveyed in the camping grounds, with the majority of camping ground survey respondents indicating that they do not know what makes up the New Zealand public notification system. It is encouraging to find that overall the public are aware of the correct actions to take in the event of a tsunami warning being issued.
Staff in hotels/motels in the Napier area were not well prepared for managing natural hazard events, with the majority of respondents having no training for dealing with emergencies, and none of those who had received training had received training for tsunami hazards.
It is recommended that steps be taken to better educate and prepare the public and tourism managers in eastern North Island communities. This will require not only public education but a range of activities that engage, empower and motivate at-risk communities to respond effectively and appropriately to tsunami warnings.

year: 2007

title: Maori and psychology: Indigenous psychology in New Zealand

authors: Nikora, Linda Waimarie

subjects: Maori

abstract: Maori have their own approaches to health and well-being, which stem from a world view that values balance, continuity, unity and purpose. The world view is not typically thought of as 'psychology', yet it is a foundation for shared understandings and intelligible action among Maori. Maori behaviours, values, ways of doing things and understandings are often not visible nor valued. However, through these opening years of the twenty-first century, psychologists are slowly turning their attention to addressing this invisibility with the explicit agenda of building 'indigenous psychologies'

text: Maori and psychology: Indigenous psychology in New Zealand Maori have their own approaches to health and well-being, which stem from a world view that values balance, continuity, unity and purpose. The world view is not typically thought of as 'psychology', yet it is a foundation for shared understandings and intelligible action among Maori. Maori behaviours, values, ways of doing things and understandings are often not visible nor valued. However, through these opening years of the twenty-first century, psychologists are slowly turning their attention to addressing this invisibility with the explicit agenda of building 'indigenous psychologies'

year: 2007