title: Deposit characteristics and dynamic processes of large volume pyroclastic density currents of the Taupo Volcanic Zone approaching and entering the sea

authors: Richmond, Mia Ani

abstract: Pyroclastic density currents (PDCs) entering the sea are a rare but dynamic phenomenon that cause significant change to the topography and bathymetry of coastal and island arc settings. Very little is known about their complex behaviour and depositional processes, as observation of such an event is uncommon and conducting experiments that simulate PDCs is challenging. A better understanding of this phenomena can aid in future volcanic monitoring and hazard management around coastal and oceanic settings.

This study combines both field observations and laboratory experiments of PDCs entering the sea. Case studies around North Island, New Zealand of pre-historic pyroclastic deposits found near the coast focused on, the Rotoiti Ignimbrite that originated from the Okataina Volcanic Centre (Pacific Coast Highway between Matata and Maketu; Mimiha Road near Matata), and the Ongatiti Ignimbrite (Glenbrook Beach, Waiuku; Kihi Road, inland of Kawhia Harbour) from the Mangakino Volcanic Centre. At each location, field observations were recorded, and samples collected, followed by grainsize and texture analysis in the laboratory (scanning electron microscopy, laser diffraction particle size analysis, dry sieving). Laboratory experiments that simulated small-scale PDCs generated by a column collapse mechanism and a dam-break mechanism into a flume were conducted.

The Ongatiti Ignimbrite at Glenbrook Beach presented flow-water interaction features through soft sediment deformations such as dewatering structures, flame structures, and thin beds of convoluted laminae. The Rotoiti Ignimbrite at Mimiha Road showed distinctive crossbedding. Both examples highlighted PDC processes after entry into the water. The Rotoiti and Ongatiti ignimbrites along the Pacific Coast Highway and Kihi Road, respectively presented typical subaerial ignimbrites that had travelled long distance overland and were still undergoing significant deposition near the coastline. The flume experiment demonstrated that PDCs segregate into two parts when entering the water, (1) a dilute overflow cloud, and (2) a dense underwater current. The entrance of pyroclastic ash material into water also generated a wave. Underwater obstructions will affect a submergent current by significantly decreasing its height and runout distance.

text: Deposit characteristics and dynamic processes of large volume pyroclastic density currents of the Taupo Volcanic Zone approaching and entering the sea Pyroclastic density currents (PDCs) entering the sea are a rare but dynamic phenomenon that cause significant change to the topography and bathymetry of coastal and island arc settings. Very little is known about their complex behaviour and depositional processes, as observation of such an event is uncommon and conducting experiments that simulate PDCs is challenging. A better understanding of this phenomena can aid in future volcanic monitoring and hazard management around coastal and oceanic settings.

This study combines both field observations and laboratory experiments of PDCs entering the sea. Case studies around North Island, New Zealand of pre-historic pyroclastic deposits found near the coast focused on, the Rotoiti Ignimbrite that originated from the Okataina Volcanic Centre (Pacific Coast Highway between Matata and Maketu; Mimiha Road near Matata), and the Ongatiti Ignimbrite (Glenbrook Beach, Waiuku; Kihi Road, inland of Kawhia Harbour) from the Mangakino Volcanic Centre. At each location, field observations were recorded, and samples collected, followed by grainsize and texture analysis in the laboratory (scanning electron microscopy, laser diffraction particle size analysis, dry sieving). Laboratory experiments that simulated small-scale PDCs generated by a column collapse mechanism and a dam-break mechanism into a flume were conducted.

The Ongatiti Ignimbrite at Glenbrook Beach presented flow-water interaction features through soft sediment deformations such as dewatering structures, flame structures, and thin beds of convoluted laminae. The Rotoiti Ignimbrite at Mimiha Road showed distinctive crossbedding. Both examples highlighted PDC processes after entry into the water. The Rotoiti and Ongatiti ignimbrites along the Pacific Coast Highway and Kihi Road, respectively presented typical subaerial ignimbrites that had travelled long distance overland and were still undergoing significant deposition near the coastline. The flume experiment demonstrated that PDCs segregate into two parts when entering the water, (1) a dilute overflow cloud, and (2) a dense underwater current. The entrance of pyroclastic ash material into water also generated a wave. Underwater obstructions will affect a submergent current by significantly decreasing its height and runout distance.

year: 2022

title: A sociocultural analysis of mandated curriculum change: the implementation of a new senior physics curriculum in New Zealand schools

authors: Fernandez, Teresa

subjects: communities of practice

abstract: We analyse the implementation of a new New Zealand physics curriculum from a socio‐cultural perspective. We explore the development of the curriculum document and examine the obstacles to its implementation. Change was compromised by the lack of any intersubjective linkage between teachers and the curriculum designers. The teachers’ own community of practice was most influential in how implementation occurred.
Curriculum change processes and discourses must be made transparent so that teachers can have a framework for ‘dereification’ of a curriculum document into their classroom practices. Without planning for teachers’ participation in the negotiation of curriculum meanings, curriculum developers themselves become marginalized, and the cultural objects they have developed will be adopted in unanticipated ways.

text: A sociocultural analysis of mandated curriculum change: the implementation of a new senior physics curriculum in New Zealand schools We analyse the implementation of a new New Zealand physics curriculum from a socio‐cultural perspective. We explore the development of the curriculum document and examine the obstacles to its implementation. Change was compromised by the lack of any intersubjective linkage between teachers and the curriculum designers. The teachers’ own community of practice was most influential in how implementation occurred.
Curriculum change processes and discourses must be made transparent so that teachers can have a framework for ‘dereification’ of a curriculum document into their classroom practices. Without planning for teachers’ participation in the negotiation of curriculum meanings, curriculum developers themselves become marginalized, and the cultural objects they have developed will be adopted in unanticipated ways.

year: 2008

title: Equity, equality, and biculturalism in the restructuring of New Zealand schools: A life-history approach

authors: Middleton, Sue

subjects: New Zealand

abstract: Interview data from the initial phase of "Monitoring Today's Schools," a research project to monitor the impact of New Zealand's educational restructuring, are examined.

text: Equity, equality, and biculturalism in the restructuring of New Zealand schools: A life-history approach Interview data from the initial phase of "Monitoring Today's Schools," a research project to monitor the impact of New Zealand's educational restructuring, are examined.

year: 1992