Rocking geology at Ōpōtiki Museum and Pecha Kucha at the Ōpōtiki Library

Recently I had the pleasure of making a presentation at the Ōpōtiki Library Pecha Kucha event, which turned out to be a fascinating evening of very interesting speakers covering a wide and diverse range of subject matter. If you are not familiar with the format, a speaker presents 20 slides, and has 20 seconds exactly to talk about each slide. The name means is a transliteration of a Japanese phrase that means "chit chat" and it was in Tokyo in 2003 that the first event was hosted. Since then this format has become very popular, in over 1000 cities, providing the ideal platform for people old and young to share stories, creative ideas, and projects.

This is the seventh night of Pecha Kucha for the Ōpōtiki Library, and each night has sold out its allocated 100 seats, proving what a popular event this is, drawing on the creativity and ideas of our wonderfully diverse community. In addition, these events have raised almost $15,000 towards fundraising for Te Tahuhu o Te Rangi, the proposed new technology and research centre for Ōpōtiki. Putting my presentation together provided an opportunity to reflect on my journey and some of the interests and ideas I like to explore in this blog, and in occasional pieces for the Eastern Bay Life So if you could not make it to Ōpōtiki, or missed out on a ticket, I would like to share my 20 images and 20 seconds of story with you, as presented on the night. However, here I invite you to explore deeper through the links I have added here.

Pecha Kucha at Ōpōtiki Library 02.08.18

  

1. Kia ora tatou, tonight I would like to share a journey from Māngere Bridge in South Auckland to Ōpōtiki, on the way exploring the whenua and our place on it. No need for a picture of myself, since I'm standing in front of you, so instead here is a picture of one of my best study companions, Sandy the geocat, sniff testing the latest samples.

2. Living in Māngere Bridge, with a passion for our natural environment, I was drawn to studying for a degree in Earth Sciences and Environmental Science. Field trips were an opportunity to explore new places, make great friends, and make the most of what the weather had to offer. The rich cultural and geological landscape I called home began to take on new depths.

3.This spectacular view became a familiar sight to me almost every day. Te Pane o Mataoho, or Māngere Mountain is one of the largest and most intact volcanic cones in Auckland, and hundreds of years ago was the centre of a complex of pā sites, gardening areas, and villages, described by some as a centre of pre-European urbanization.

4. The maunga is home to the Māngere Mountain Education Centre, a "living museum" where people can learn the history of Te Waiohua communities who shaped this whenua and were shaped by it. Here one may walk the maunga with its historical and archaeological sites; and learn about the geology of this volcano that erupted 70 000 years ago.

5. Drawing on my passion for the geology of the area, and contributing to the centre as a volunteer, I came to understand the importance of this maunga and others as sacred spaces that held a history of thriving and dynamic communities, as shown in this picture based on archaelogical evidence and oral histories.

6. Exploring the histories of the communities that thrived and grew over the centuries on these fertile volcanic soils, I was beginning to see how the geology of the area shaped  society, and in turn society modified the environment to their advantage, sustainably providing for their people over generations.

7. Researching the geology and history of Auckland, I was shocked to discover the history of degradation and destruction of its volcanic features by quarrying, urban encroachment, or simply because maunga were considered inconvenient. Nowhere was this more evident than on a South Auckland peninsula called Ihumātao.

8. In time I became involved with the Save Our Unique Landscapes fighting a housing development adjacent to the Otuataua Stonefields Historic Reserve at Ihumātao. The site of the earliest settlement in Tāmaki Makaurau, and here one finds the human, geological, and environmental history written in the landscsape.

9. Getting to know this whenua from a scientific and cultural perspective and building a relationship with whanau fighting to protect it, taught me how to read the stories the whenua tells us, and placed its geological story in a living cultural context. Geology is just one aspect among many, of the story of how we came to stand where we do today.

10. Studying a variety of subjects and disciplines was a very exciting and rewarding process that opened a whole new way of looking, learning, and communicating for me. I now enjoy sharing this with others and can see people light up when they engage with the whenua and its stories we find both on and below the surface. In essence, we become time travelers.

11. So, from South Auckland we have come to Ōpōtiki in the Eastern Bay of Plenty, a very different landscape from my previous home. I look forward to exploring  this geologically diverse and culturally rich area and would like to share with you a geological perspective on where we presently stand that may be new to you.

12. First, I would like to introduce you to the concept of geological time, illustrated here with an appropriate visual aid. So, we see on this scale the entire span of human history is a mere layer of bubbles on the foam of a glass of beer, representing the four-billion-year history of our planet.

13. Viewing the landscape in the context of the geological timescale, we can see that nothing stands still. Erosion and deposition are continuous cyclic processes. Sediments become buried and turn to rock, rocks are uplifted and eroded. Mountains become deformed, sheared and brittle, and earthquakes  rock and reshape our landscapes.

14. Volcanism, a force feared by humans since recorded history is a neccesary force in creating new land, and forming our mineral rich and fertile volcanic soils. From Ōpōtiki we see White Island, where the Taupō Volcanic Zone extends  to the world's longest chain of active submarine volcanoes and hydrothermal vents, stretching to Tonga.

15. Closer to Ōpōtiki and on land, the Taupō Volcanic Field sits atop a rift in the crust spreading at around 9mm per. year. In this area the crust is only 16km thick, half the usual 30km thick, and there is evidence of a magma body 50 by 160 kilometres just 10 kilometres below the surface.

16. While Ōpōtiki does not sit within the Taupō Volcanic Zone, massive eruptions have shaped our land, provided raw materials for our soils, and smothered the land with pumice and ash for hundreds of square kilometres. In a road cutting at Kutarere, we see pumice a metre thick, erupted from 70 kilometres away.

Other clues in today's landscape tell of constant change and catastrophic events. Gravels deposited during an ice-age six hundred thousand years ago are seen in coastal cliffs at Waiotahi. Above these sit ash deposits from the Taupō Volcanic Zone, first erupting some three hundred thousand years ago.

18. New Zealand is a country on the rise, the whenua we call home a small portion of the mostly submerged continent of Zealandia. The same processes that stretch and pull the crust of the Taupō Volcanic Zone, thrust, fold, and distort the rocks of the Ruakumara Ranges, while rainfall and earthquakes assist the erosion of these brittle slopes.

19. While these geological processes may seem rather abstract, they have in fact provided resources since the arrival of the first humans in this country. We see signs of this early relationship with geology in the placement of pā, the types of rock favoured for tools, and the widely traded obsidian from Mayor Island found as far as the Kermadecs.

20. I hope you have enjoyed this journey with me through our dynamic whenua. I invite you to explore further through my blog Aotearoa Rocks, my facebook page Māngere Bridge Rocks, and to check out the developing geological display at the Ōpōtiki Museum. And of course, thank you to the Ōpōtiki Library for organizing this great event.

Rocking the Ōpōtiki Museum!


Over the past year I have had the pleasure of working on refreshing the geological display at Ōpōtiki Museum, adding new material and providing interpretation. I would like to share some brief glimpses of the display, and encourage you to check out the full display at the museum, along with a wealth of other historical material from the Eastern Bay of Plenty. open Monday to Friday 10am till 4pm, and Saturday 10am till 2pm, at 123 Church Street, Ōpōtiki. 

Above and below. Distinctive yellow sulphur crystals from Whakaari/White Island. 
Sulphur mining took place on the island till the late 1930's.

Pumice can be found throughout the Bay of Plenty, mostly originating from
the Taupo Volcanic Zone. It can come in a variety of colours depending on
mineral content, with some pieces showing flow banding. Pumice on Eastern
Bay of Plenty may have washed ashore from White Island, or even as from as
far as underwater volcanoes in the Tonga Kermadec Arc.

Obsidian is formed when silica-rich rhyolotic lava rapidly cools and crystals 
are unable to form. This volcanic glass displays a conchoidal fracture and
leaves sharp edges, meaning it was used by Māori for scraping and
cutting tools. Pumice is also formed by rhyolitic lava, but is erupted in a 
gaseous manner, and gas bubbles are preserved when the lava cools.

Detail of pumice, showing gas bubbles preserved in volcanic glass.
Pumice can be up to 90% air, and can float in water.

Unusual grey coloured pumice/volcanic glass, washed up on
Ōhope Beach, most likely from Whakaari/White Island.

Rhyolitic volcanic ash on the left, andesitic tephra on the right. Rhyolotic ash
has a high silica content, hence the pale colour. Coarse tephra is from Ruapehu,
while the ash is from Kutarere, around 70km from the original eruption source.

Unless otherwise credited, all images in pecha kucha and this post by author.

Thanks to the Eastern Bay Life Magazine, published by the Whakatāne Beacon, for publishing regular pieces on the natural history of the Bay of Plenty. Follow the links below 
to view, reproduced with the permission of the Whakatane Beacon.

Fire, ice and dust. Ice Age in The Bay of Plenty.

Ice Age rocks Waiotahi

Waioeka, Waters of the weka