20 Jan 2021

Volcanologists preparing Aucklanders for eruptions

From Summer Times 2020/2021, 9:20 am on 20 January 2021

Is your house ready for a direct hit from a volcano? A team of scientists is researching just how hard urban volcanoes hit to try and help Aucklanders prepare for an eruption. 

Among other things this has involved building simulations of roofs and firing volcanic rocks at them. But it's not just rocks we have to worry about.

Disaster risk and resilience Professor Tom Wilson from the University of Canterbury is leading the team looking into this and tells Summer Times Auckland is sitting on around 53 known volcanic centres.

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Photo: 123RF

Wilson says that within someone’s lifetime, there’s around a 5-15 percent chance of a volcanic eruption.

“It’s relatively low within our lifetime but its worth thinking about the nature of the risk for Auckland from that volcanic field.”

While people don’t necessarily need to do anything on an individual basis, the consequences of an eruption are so severe it’s worth planning from a public agency point of view.

“Things like making sure EQC is really well prepared and has a good understanding of what might happen and how critical infrastructure might need to be designed or operate during a crisis like that.”

Wilson says Auckland eruptions in the past have tended to be relatively small apart from Rangitoto’s last eruption around 600 years ago.

He says Aucklanders would get warning of an eruption because GNS science has a number of seismographs positioned around the city in key volcanic areas which would pick up the movement of magma.

“As that magma comes up, we’d probably start to feel those earthquakes… that’s when you’d be initiating evacuations as you’re trying to pinpoint where that eruption may come out at the surface.

When that magma breaches the surface, Wilson says there’s two things that can happen. The first is that it might interact with water.

“If it does that, you can get quite vigorous explosions where a shockwave is produced.”

He says the pressure and explosions could knock down buildings and would create hot gas clouds.

“In addition to that, you may get a lot of ballistic projectiles produced.”

The other option, where the magma doesn’t interact with water as it comes up, you get what Wilson describes as a dry eruption.

“You get these spectacular fire fountains of lava being ejected up into the atmosphere. They look quite amazing and those are what builds the cones that we see across the Auckland landscape.”

A dry eruption can lead to lava flows, but Wilson says they would anticipate it to be much less damaging than the alternative.

While New Zealand buildings are built to relatively high standards, Wilson’s team is looking at how an eruption could affect and damage them.

“We’ve got good earthquake and weather codes, but we don’t necessarily build explicitly to be volcano resistant.”

He says that there’s no indications that Auckland is going to experience an eruption in the near future but, one way or another, it will eventually happen.

“We need to think about this in a risk context. Whilst the likelihood is quite low, it’s well worth planning for so that if and when it looks like there could be an eruption in Auckland, we’ve done the backbone planning.”

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