Behind the Scenes

Today some DEVORA researchers (including myself) were filmed doing some fieldwork at some volcanic craters in Puhinui Reserve, near the Auckland airport. The craters were unrecognised as volcanoes until 2011, when researchers from Geomarine Research revealed their true nature. The objective of our fieldwork was to learn a little more about them. You can watch the piece, which aired on ONE News on Sunday, 28 April, here. 


This study today was only a small part of a larger study on base surges in the Auckland field. When magma comes into contact with water, it results in a powerful explosion, which may create a base surge. Base surges are very fast-moving (around 100 m/s, or 360 km/hr), hot clouds of gas and ash that expand away, along the ground, in every direction from the explosion site. They leave tell-tale deposits behind that we can study. Interestingly, there is evidence for base surges on Mars.

Auckland is quite a wet place–we are surrounded by the sea, and we also have lakes and a lot of groundwater. So it makes sense that we see evidence that a majority of the 53 volcanoes in the Auckland Volcanic Field started with explosive base surges created when magma came into contact with water. Darren Gravley and his team at University of Canterbury are using Ground Penetrating Radar (or “GPR”) to study base surge deposits from several AVF volcanoes of different sizes. They want to figure out how far and fast the base surges traveled, partly to understand how large of an area to evacuate before an eruption. The information may also be used to model the impact of future base surges on Auckland buildings.

I’ll let some pictures tell the story from today (credit: Cheng Yii Sim)


Prior to filming–setting up the Ground Penetrating Radar equipment. Transmitter of radio waves on left (by Jill Kenny) and receiver on right (by Elaine Smid). Simon Aiken (centre) is holding the computer unit that receives the data. Dan Hikuroa (left centre) for scale and moral support/swap-in. We took measurements every half a meter for 370 m–tape measure can be seen on the ground between Dan and Simon.


Filming begins! Very exciting, but pretty easy to act natural. We had a job to do!


The part that made the cut, explaining what we’re looking for. Took me about 6-7 takes. That hill rising gently in the background with the water tanks is part of the tuff ring of one of the volcanic craters.


Darren Gravley explains base surges to the cameras.


What the ground looks like under our feet. Fantastic data recovery in some spots! Not so good in others, where the ground was soggy from all the recent rain…the GPR doesn’t work very well under those conditions.


The survey track (white line along ground from bottom right is tape measure). You’d hardly believe this was a volcanic crater, would you? No wonder it wasn’t discovered until 2011.

20lookign at data good

Looking at the data, being science-y.

17sci smiling

The team, from l-r: Jill Kenny, Elaine Smid, Dan Hikuroa, Simon Aiken. Missing: Darren Gravley and our photographer, Cheng Yii Sim.

I want to thank Science Media Centre NZ, particularly the Science Media SAVVY course leaders, TVNZ’s Will Hine, fantastic camera man Bruce, and our research team for making it a great day for science and science outreach: 

Darren Gravley

Simon Aiken (he’s first on this link’s list)

Dan Hikuroa

Jill Kenny

Cheng Yii Sim 

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