title: Modelling volcanic tsunamis

authors: Prasetya, Gegar Sapta

subjects: tsunamis

abstract: Tsunamis generated by volcanic eruptions have caused about 25% of all deaths associated with volcano activity. The 1883 Krakatau eruption is one example of a fairly recent eruption that produced large tsunamis (-35 m) which caused a high death toll. Concern has also been raised by the potential tsunami generation of the Auckland Volcanic Field, and the impact of such events on the Auckland Region.
Although the generation of tsunamis by volcanic eruptions is a major hazard, the processes of tsunami generation are poorly understood. A review of volcanic tsunamis identified 10 main mechanisms. Four of these - caldera collapse, debris avalanches, submarine explosions, and pyroclastic flows - have been suggested as the mechanisms producing the largest tsunamis. All four mechanisms have also been suggested as being responsible for the tsunamis produced by the Krakatau eruption.
A combination of physical and numerical modelling was used to develop predictive tools to be applied to volcanoes in Indonesia and New Zealand. The physical modelling involved two main investigations:
• A 3 dimensional scale model of the Straits of Sunda and Krakatau. This examined the nature of tsunamis produced by caldera collapse, submarine explosions, and water displacement by debris avalanches and pyroclastic flows.
• A series of 2 dimensional simulations of the entrance of pyroclastic flows into the sea. A finite element numerical model was applied to the simulation of pyroclastic flow, maar formation and submarine explosion generation of tsunamis within the Auckland Volcanic Field.
The physical and numerical model results indicate that large scale pyroclastic flows are probably the cause of the main 1883 Krakatau tsunamis. A tsunami wave can easily be generated by gravity flows entering the water, regardless of the slope. The wave properties depend on the relative densities of the flow and the receiving body, and the velocity of the flow. The angle of entry of the flow into the water determines the deposition pattern of sediment. The formation of the Calmeyers and Steers shallow area on Krakatau event 1883 was reproduced by the pyroclastic experiments using coarse sand and mud with steep entry angle ~ 60°). The more dilute upper component of the pyroclastic flow that traveled along the sea surface for up to 45 km and killed more than 1000 people at Katimbang, Sumatera Island can also be explained. The experiments showed that less dense material from the pyroclastic flow propagates near the water surface. This is even more likely if the material is hot and gas-rich.
Physical and numerical model results showed that a single explosion cannot produce a high wave. If a super violent explosion did occur during the Krakatau event, then the water waves (tsunamis) that caused the devastating effect on the surrounding island coastal land were not caused by the direct transfer of explosive forces. Instead a sequence of one or more pyroclastic flows, or collapsing column in and around the Krakatau complex are the most likely mechanism causing the largest tsunami.
Numerical modelling of the Auckland Volcanic Field examined 4 scenarios:
• A series of submarine explosion;
• Pyroclastic flows from Rangitoto Island;
• Pyroclastic flows from Browns (Motukorea) Island;
• Submarine explosion within the Tamaki Estuary.
The first 3 scenarios produced regional effects, while the last was purely local event.
It was also found that the efficiency of the submarine explosion mechanism was increased by using a sequence of smaller explosions, instead of one large explosion. However the timing between explosions was found to be critical; if the explosions are too close together or too far apart, the efficiency decreases. It is considered that the optimal timing will vary with water depth and explosive yield.
The numerical modelling showed that volcanic tsunamis are not a major threat to Auckland. However under suitable conditions a volcanic eruption could produce moderately large tsunamis that generate strong currents.

text: Modelling volcanic tsunamis Tsunamis generated by volcanic eruptions have caused about 25% of all deaths associated with volcano activity. The 1883 Krakatau eruption is one example of a fairly recent eruption that produced large tsunamis (-35 m) which caused a high death toll. Concern has also been raised by the potential tsunami generation of the Auckland Volcanic Field, and the impact of such events on the Auckland Region.
Although the generation of tsunamis by volcanic eruptions is a major hazard, the processes of tsunami generation are poorly understood. A review of volcanic tsunamis identified 10 main mechanisms. Four of these - caldera collapse, debris avalanches, submarine explosions, and pyroclastic flows - have been suggested as the mechanisms producing the largest tsunamis. All four mechanisms have also been suggested as being responsible for the tsunamis produced by the Krakatau eruption.
A combination of physical and numerical modelling was used to develop predictive tools to be applied to volcanoes in Indonesia and New Zealand. The physical modelling involved two main investigations:
• A 3 dimensional scale model of the Straits of Sunda and Krakatau. This examined the nature of tsunamis produced by caldera collapse, submarine explosions, and water displacement by debris avalanches and pyroclastic flows.
• A series of 2 dimensional simulations of the entrance of pyroclastic flows into the sea. A finite element numerical model was applied to the simulation of pyroclastic flow, maar formation and submarine explosion generation of tsunamis within the Auckland Volcanic Field.
The physical and numerical model results indicate that large scale pyroclastic flows are probably the cause of the main 1883 Krakatau tsunamis. A tsunami wave can easily be generated by gravity flows entering the water, regardless of the slope. The wave properties depend on the relative densities of the flow and the receiving body, and the velocity of the flow. The angle of entry of the flow into the water determines the deposition pattern of sediment. The formation of the Calmeyers and Steers shallow area on Krakatau event 1883 was reproduced by the pyroclastic experiments using coarse sand and mud with steep entry angle ~ 60°). The more dilute upper component of the pyroclastic flow that traveled along the sea surface for up to 45 km and killed more than 1000 people at Katimbang, Sumatera Island can also be explained. The experiments showed that less dense material from the pyroclastic flow propagates near the water surface. This is even more likely if the material is hot and gas-rich.
Physical and numerical model results showed that a single explosion cannot produce a high wave. If a super violent explosion did occur during the Krakatau event, then the water waves (tsunamis) that caused the devastating effect on the surrounding island coastal land were not caused by the direct transfer of explosive forces. Instead a sequence of one or more pyroclastic flows, or collapsing column in and around the Krakatau complex are the most likely mechanism causing the largest tsunami.
Numerical modelling of the Auckland Volcanic Field examined 4 scenarios:
• A series of submarine explosion;
• Pyroclastic flows from Rangitoto Island;
• Pyroclastic flows from Browns (Motukorea) Island;
• Submarine explosion within the Tamaki Estuary.
The first 3 scenarios produced regional effects, while the last was purely local event.
It was also found that the efficiency of the submarine explosion mechanism was increased by using a sequence of smaller explosions, instead of one large explosion. However the timing between explosions was found to be critical; if the explosions are too close together or too far apart, the efficiency decreases. It is considered that the optimal timing will vary with water depth and explosive yield.
The numerical modelling showed that volcanic tsunamis are not a major threat to Auckland. However under suitable conditions a volcanic eruption could produce moderately large tsunamis that generate strong currents.

year: 1998

title: Things inside things

authors: Thornley, Jessica

abstract: Things Inside Things is a collection of autofiction that revolves around a single mother and her two young daughters. It is at once an intimate account of single motherhood and an ode to, a call to arms for, the maternal bond as irreducible, sacred–the thing at the centre of all things. 

Made up of fragmentary scenes, poetic prose, and short stories, the narrative moves back and forth in time, across hemispheres, through shifting points of view and recurrent characters   painting readers into the living and breathing layers of one single mother’s experience and world. 

Taking inspiration from writers Katherine Mansfield and Lucia Berlin, Things Inside Things bucks linear plot convention for a form that is voiced, sensory and shaped by the physicality of emotion. 

If this is a collection that advocates for the joy, reward and importance of the mother-child bond it is also one in which that bond does not come easy. Inside the walls and skin of these stories a mother seeks help for chronic maternal anxiety, navigates the loss of relationship break down with her children’s father, holds space for paternal and cultural ties that must span distance, be sustained over Zoom calls, and navigates the emotional and material weight of mothering alone. 

Above all this is body of work that seeks to hold ordinary, domestic days to the light. That pays homage to the everyday maternal and relational moments of connection, rupture and repair that shape who we are and can–if we let them–transform us. These are not stories of martyrdom. Rather, they give us motherhood as a creative, radical and transcendent force. Where a daughter’s ‘sturdy seven-year-old legs with downy hairs intact and lit up are holier than all the Gods of all religions’, where female friendship is a haven of ‘light, smile lines, vast and loyal as the seasons’ and within which we witness a mother, a woman, a writer finding herself on the page.

text: Things inside things Things Inside Things is a collection of autofiction that revolves around a single mother and her two young daughters. It is at once an intimate account of single motherhood and an ode to, a call to arms for, the maternal bond as irreducible, sacred–the thing at the centre of all things. 

Made up of fragmentary scenes, poetic prose, and short stories, the narrative moves back and forth in time, across hemispheres, through shifting points of view and recurrent characters   painting readers into the living and breathing layers of one single mother’s experience and world. 

Taking inspiration from writers Katherine Mansfield and Lucia Berlin, Things Inside Things bucks linear plot convention for a form that is voiced, sensory and shaped by the physicality of emotion. 

If this is a collection that advocates for the joy, reward and importance of the mother-child bond it is also one in which that bond does not come easy. Inside the walls and skin of these stories a mother seeks help for chronic maternal anxiety, navigates the loss of relationship break down with her children’s father, holds space for paternal and cultural ties that must span distance, be sustained over Zoom calls, and navigates the emotional and material weight of mothering alone. 

Above all this is body of work that seeks to hold ordinary, domestic days to the light. That pays homage to the everyday maternal and relational moments of connection, rupture and repair that shape who we are and can–if we let them–transform us. These are not stories of martyrdom. Rather, they give us motherhood as a creative, radical and transcendent force. Where a daughter’s ‘sturdy seven-year-old legs with downy hairs intact and lit up are holier than all the Gods of all religions’, where female friendship is a haven of ‘light, smile lines, vast and loyal as the seasons’ and within which we witness a mother, a woman, a writer finding herself on the page.

year: 2024-11-15

title: Early childhood teachers partnering with teacher educators to connect children to taiao (the natural world) through place-based learning

authors: Postlewaight, Gillian

abstract: Initial cycles of an action research project brought together local early childhood (ECE) teachers, and tertiary ECE teacher educators, to explore possible uses of the Ōtātara Outdoor Learning Centre (ŌOLC), adjoining the campus at Hawke’s Bay’s Te Aho a Maui Eastern Institute of Technology (EIT), Napier, New Zealand. EIT is situated below Ōtātara Pa, a historic site that holds cultural and historical significance for local Māori, specifically Ngati Pārau Hapū and Ngati Kahungunu Iwi. Education in New Zealand is underpinned by commitment to Te Tiriti o Waitangi (Treaty of Waitangi), ensuring that the principles; partnership, participation and protection of kaupapa Māori are supported through bicultural curricula. Māori holistic perspectives strengthen this focus and shifting understanding that place-based learning authenticates environmental approaches to education and cultural knowledge. During the first meeting, participants walked the hillside site and shared group discussions. From these conversations, the teachers identified three main themes: establishing connections between children and the physical place, new opportunities for teacher learning and challenges to implementing spontaneous teaching and learning in this unique environment. Future cycles of the research will focus on workshops for teachers to address these themes for teachers’ working with children in the space.

text: Early childhood teachers partnering with teacher educators to connect children to taiao (the natural world) through place-based learning Initial cycles of an action research project brought together local early childhood (ECE) teachers, and tertiary ECE teacher educators, to explore possible uses of the Ōtātara Outdoor Learning Centre (ŌOLC), adjoining the campus at Hawke’s Bay’s Te Aho a Maui Eastern Institute of Technology (EIT), Napier, New Zealand. EIT is situated below Ōtātara Pa, a historic site that holds cultural and historical significance for local Māori, specifically Ngati Pārau Hapū and Ngati Kahungunu Iwi. Education in New Zealand is underpinned by commitment to Te Tiriti o Waitangi (Treaty of Waitangi), ensuring that the principles; partnership, participation and protection of kaupapa Māori are supported through bicultural curricula. Māori holistic perspectives strengthen this focus and shifting understanding that place-based learning authenticates environmental approaches to education and cultural knowledge. During the first meeting, participants walked the hillside site and shared group discussions. From these conversations, the teachers identified three main themes: establishing connections between children and the physical place, new opportunities for teacher learning and challenges to implementing spontaneous teaching and learning in this unique environment. Future cycles of the research will focus on workshops for teachers to address these themes for teachers’ working with children in the space.

year: 2023-04-27