title: The nature and dynamics of the Rotorua eruptive episode, Okataina Volcanic Centre, Taupo Volcanic Zone

authors: Kilgour, Geoff

subjects: Volcanic hazard analysis

abstract: The 15.7 cal yrs B.P. Rotorua eruptive episode is the latest expression of western Okataina volcanism. Okataina is one of the world's most active rhyolitic volcanoes and this eruptive episode provides an ideal opportunity to examine the nature, dynamics and impacts of a large magnitude explosive eruption from this volcanic centre.

This re-investigation of the Rotorua eruptive episode has lead to the grouping of the deposits into two distinct phases of eruption. The Rotorua Tephra and Eastern Dome (previously thought to be Te Rere-related) are termed 'Rotorua A' phase. Trig 7693 andMiddle domes (previously linked to the source of the Rotorua Tephra) have been grouped with the Upper Rotorua Tephra into the. 'Rotorua B' phase. These groupings are predominantly based on mineralogy and geochemistry on samples of pyroclastic and dome deposits.

The eruptive sequence began with a small initial ash without a basalt trigger, followed soon after by a plinian fall deposit (1.62 km³) directed to the NW. Dome growth ensued (Eastern dome), creating an extensive rhyolite dome (0.72 km³) in the Okareka Embayment. Soon after Eastern dome growth (based on the absence of paleosol development) the Rotorua B phase was initiated. This phase of predominant effusive dome growth lead to the construction of the coalesced Trig 7693 and Middle domes. Periodic vulcanian explosions and dome collapses lead to the localised dispersal to the S and E, of pyroclastic density currents and fall.

A new age of 12941 ± 75 ¹⁴C years BP was obtained from charcoal in a surge deposit at a proximal site. This results in a revised age for the Rotorua eruption of 15 700 cal yrs BP. The eruption duration is estimated to exceed 15 yrs, based on a total dome volume of 1.37 km³, assuming a growth rate of 3 m ³/s.

To the NW, the Rotorua A plinian deposit (Ap-1 to Ap-10 sub units) is overall normally graded, however cm-scale bedding is evident throughout the deposit. The grain size ranges from a block-sized, basal sub unit to a medium ash, upper. The plinian tephra is biotite-poor compared to the distinct Rotorua B deposits (previously 'Upper Rotorua Tephra'), which is biotite-rich.

Whole rock geochemistry on the Rotorua A pyroclastics, forms an apparent trend, suggesting the magma supplying the explosive phase was compositional zoned prior to eruption and was subsequently disrupted immediately prior to or during eruption. The Rotorua A and B phases plot as distinct clusters in all binary element plots. Intensive parameters calculated on Fe-Ti oxides highlights the distinction between Rotorua A (Rotorua Tephra and Eastern Dome) and Trig 7693 and Middle domes. Isotopic evidence indicates the Trig 7 693 and Middle domes were supplied by a separate magma
batch to the Rotorua A phase, suggesting small ( <1 km³) magma batches were residing in close proximity.

An eruption of this size today would cause the total destruction of Rotorua City (home to >50,000 people) due to ~ 1.5 m of volcanic ejecta accumulating in this region. This would cripple the central North Island for weeks to months. Due to the length of the eruption, mitigation would be required for an extended period after the initial phase of the eruptive episode. Livestock would be severely affected from blanketing tephra, along with the complete collapse of intensive forestry operations in the Rotorua District. National and international flights from Hamilton and Auckland airports would be heavily disrupted causing major economic losses. Respiratory problems and contaminated water intake would continue for a long period after the cessation of volcanic activity.

text: The nature and dynamics of the Rotorua eruptive episode, Okataina Volcanic Centre, Taupo Volcanic Zone The 15.7 cal yrs B.P. Rotorua eruptive episode is the latest expression of western Okataina volcanism. Okataina is one of the world's most active rhyolitic volcanoes and this eruptive episode provides an ideal opportunity to examine the nature, dynamics and impacts of a large magnitude explosive eruption from this volcanic centre.

This re-investigation of the Rotorua eruptive episode has lead to the grouping of the deposits into two distinct phases of eruption. The Rotorua Tephra and Eastern Dome (previously thought to be Te Rere-related) are termed 'Rotorua A' phase. Trig 7693 andMiddle domes (previously linked to the source of the Rotorua Tephra) have been grouped with the Upper Rotorua Tephra into the. 'Rotorua B' phase. These groupings are predominantly based on mineralogy and geochemistry on samples of pyroclastic and dome deposits.

The eruptive sequence began with a small initial ash without a basalt trigger, followed soon after by a plinian fall deposit (1.62 km³) directed to the NW. Dome growth ensued (Eastern dome), creating an extensive rhyolite dome (0.72 km³) in the Okareka Embayment. Soon after Eastern dome growth (based on the absence of paleosol development) the Rotorua B phase was initiated. This phase of predominant effusive dome growth lead to the construction of the coalesced Trig 7693 and Middle domes. Periodic vulcanian explosions and dome collapses lead to the localised dispersal to the S and E, of pyroclastic density currents and fall.

A new age of 12941 ± 75 ¹⁴C years BP was obtained from charcoal in a surge deposit at a proximal site. This results in a revised age for the Rotorua eruption of 15 700 cal yrs BP. The eruption duration is estimated to exceed 15 yrs, based on a total dome volume of 1.37 km³, assuming a growth rate of 3 m ³/s.

To the NW, the Rotorua A plinian deposit (Ap-1 to Ap-10 sub units) is overall normally graded, however cm-scale bedding is evident throughout the deposit. The grain size ranges from a block-sized, basal sub unit to a medium ash, upper. The plinian tephra is biotite-poor compared to the distinct Rotorua B deposits (previously 'Upper Rotorua Tephra'), which is biotite-rich.

Whole rock geochemistry on the Rotorua A pyroclastics, forms an apparent trend, suggesting the magma supplying the explosive phase was compositional zoned prior to eruption and was subsequently disrupted immediately prior to or during eruption. The Rotorua A and B phases plot as distinct clusters in all binary element plots. Intensive parameters calculated on Fe-Ti oxides highlights the distinction between Rotorua A (Rotorua Tephra and Eastern Dome) and Trig 7693 and Middle domes. Isotopic evidence indicates the Trig 7 693 and Middle domes were supplied by a separate magma
batch to the Rotorua A phase, suggesting small ( <1 km³) magma batches were residing in close proximity.

An eruption of this size today would cause the total destruction of Rotorua City (home to >50,000 people) due to ~ 1.5 m of volcanic ejecta accumulating in this region. This would cripple the central North Island for weeks to months. Due to the length of the eruption, mitigation would be required for an extended period after the initial phase of the eruptive episode. Livestock would be severely affected from blanketing tephra, along with the complete collapse of intensive forestry operations in the Rotorua District. National and international flights from Hamilton and Auckland airports would be heavily disrupted causing major economic losses. Respiratory problems and contaminated water intake would continue for a long period after the cessation of volcanic activity.

year: 2002

title: Acceptance with joy: Writing as a means of embodying compassion

authors: Kotzé, Elmarie

subjects: outsider witnessing

abstract: This article reports on research using writing workshops conducted with three women who distanced themselves from problematic relationships with their bodies that were induced by eating disorders. The article focuses on the use of writing tasks based on appreciative inquiry and outsider witnessing processes, practised with a group of women in a manner that provided space for the participants to story compassion for their bodies. The article explores the writing tasks that the participants were invited to undertake, and discusses the subsequent interviewing and outsider witnessing process as forms of narrative therapy practice. The article also documents the process of capturing a participant’s voice in a rescued speech poem.

text: Acceptance with joy: Writing as a means of embodying compassion This article reports on research using writing workshops conducted with three women who distanced themselves from problematic relationships with their bodies that were induced by eating disorders. The article focuses on the use of writing tasks based on appreciative inquiry and outsider witnessing processes, practised with a group of women in a manner that provided space for the participants to story compassion for their bodies. The article explores the writing tasks that the participants were invited to undertake, and discusses the subsequent interviewing and outsider witnessing process as forms of narrative therapy practice. The article also documents the process of capturing a participant’s voice in a rescued speech poem.

year: 2014

title: Traditional plant harvesting in contemporary fragmented and urban landscapes

authors: Wehi, Priscilla M.

subjects: ethnobiology

abstract: Ecosystem fragmentation and destruction can lead to restrictive administration policies on traditional harvesting by indigenous peoples from remaining ecosystem tracts. In New Zealand, concerns about endangered species and governmental policies that focus on species and ecosystem preservation have resulted in severely curtailed traditional harvesting rights. Although provision has been made for limited gathering of traditional plants from government-administered conservation lands, it is unclear how much harvesting is undertaken on these lands and elsewhere and what this harvest might consist of. We interviewed seven expert Maori elders from the Waikato, New Zealand, to identify plant species they currently harvested and from where. We compared these data with the data we collected on permits issued for plant collecting on conservation lands in the same region. We sought to gain information on indigenous plant harvesting to determine the extent of permitted harvesting from conservation lands in the Waikato and to identify issues that might affect plant harvesting and management. Elders identified 58 species they harvest regularly or consider culturally important; over 50% of these species are harvested for medicinal use. Permit data from 1996 to 2006 indicated no apparent relationship between species of reported cultural significance and the number of permits issued for each of these species. Currently, few plant species are harvested from conservation lands, although some unofficial harvesting occurs. Elders instead reported that medicinal plants are frequently collected from urban and other public areas. They reported that plant species used for dyeing, carving, and weaving are difficult to access. Elders also discussed concerns such as spraying of roadsides, which resulted in the death of medicinal species, and use of commercial hybrids in urban planning. Local government may have an increasingly important role in supporting native traditions through urban planning, which takes account of cultural harvesting needs while potentially reducing future harvesting pressure on conservation lands. We suggest that active participation by the Māori community in the development and management of urban harvesting resources will result in positive outcomes.

text: Traditional plant harvesting in contemporary fragmented and urban landscapes Ecosystem fragmentation and destruction can lead to restrictive administration policies on traditional harvesting by indigenous peoples from remaining ecosystem tracts. In New Zealand, concerns about endangered species and governmental policies that focus on species and ecosystem preservation have resulted in severely curtailed traditional harvesting rights. Although provision has been made for limited gathering of traditional plants from government-administered conservation lands, it is unclear how much harvesting is undertaken on these lands and elsewhere and what this harvest might consist of. We interviewed seven expert Maori elders from the Waikato, New Zealand, to identify plant species they currently harvested and from where. We compared these data with the data we collected on permits issued for plant collecting on conservation lands in the same region. We sought to gain information on indigenous plant harvesting to determine the extent of permitted harvesting from conservation lands in the Waikato and to identify issues that might affect plant harvesting and management. Elders identified 58 species they harvest regularly or consider culturally important; over 50% of these species are harvested for medicinal use. Permit data from 1996 to 2006 indicated no apparent relationship between species of reported cultural significance and the number of permits issued for each of these species. Currently, few plant species are harvested from conservation lands, although some unofficial harvesting occurs. Elders instead reported that medicinal plants are frequently collected from urban and other public areas. They reported that plant species used for dyeing, carving, and weaving are difficult to access. Elders also discussed concerns such as spraying of roadsides, which resulted in the death of medicinal species, and use of commercial hybrids in urban planning. Local government may have an increasingly important role in supporting native traditions through urban planning, which takes account of cultural harvesting needs while potentially reducing future harvesting pressure on conservation lands. We suggest that active participation by the Māori community in the development and management of urban harvesting resources will result in positive outcomes.

year: 2010