Writings on technology and society from Wellington, New Zealand

Thursday, September 27, 2007

Volcanos and Earthquakes!

Today on Radio New Zealand National I talked about volcanos and earthquakes and what you can find out about them on the Internet. The New Zealand web site GeoNet tells you all about volcanic and seismic activity. Read on for my notes and the links at the end.

Q: Now to volcanoes – topical, with Mt Ruapehu doing its thing?

A: Yes – you have to think in geological time, that’s millions or even billions of years when you are dealing with volcanoes and earthquakes. Ruapehu seems to go off every decade or two – that’s pretty much continuously as far as the age of the planet is concerned.

Q: Obviously scientists use technology to monitor volcanos and earthquakes.

A: Yes, there’s a lot to it. They have seismographs which measure rapid ground movements.

Q: They measure earthquakes you mean?

A: Yes, these are machines where a pen draws a line on a rotating drum of paper. They are probably all electronic now – I doubt there is still paper involved – but online they still show you what looks like a pen trace up and down as the earthquake progresses.

Q: And that shows the actual ground movement?

A: It shows the ground acceleration. You can work the movement out from that.

Q: You said these things are online?

A: That’s the beauty of it. Earthquakes and volcanos are monitored in New Zealand by Geological and Nuclear Sciences, which is a Crown Research Institute, one of the descendents of the old DSIR. It lives in the former Avalon TV studios out in Lower Hutt. GNS gathers a huge amount of information that is used by its own scientists and by scientists around the world, and it publishes the lot online for free.

The website that GNS puts all this information up on is called GeoNet and it’s in the links for today’s programme. GeoNet has web cameras for all the volcanos. There was a webcam picture of Ruapehu taken from around the Chateau on the front page of the site yesterday – the picture’s probably still there today. You can see how the top ridge of the mountain is stained dark grey by the volcanic ash. Looking at the picture, you can get a feel for how Ruapehu would have looked thousands of years ago when it was a complete cone like Ngauruhoe is today.

Q: It used to be a cone?

A: Yes, so the scientists tell us, and it does look like the bottom part of one.

Q: So what happened to it?

A: It may have blown its top off, like Mount St Helens did in the US in the 1980s, or perhaps it was just erosion.

On GeoNet you can see monitoring information about all New Zealand volcanoes that are considered live, including Mt Taranaki, Lake Taupo, and Auckland City.

Q: Auckland is live? Which volcano?

A: Oh yes, it’s live alright. Analysing the ages of the volcanic cones there shows that a new one comes up every few centuries. In geological terms it’s a young, active, volcanic field. So there’s no room for smugness in Auckland towards Wellington about our active fault line!

And Lake Taupo’s last eruption is thought to have been the biggest eruption anywhere on the planet in the last five thousand years.

As well as volcanos the GeoNet site also has a lot of information about earthquakes, including a list of all the recent New Zealand shakes. Every time there’s a shake in Wellington the site gets hit with a lot of traffic as everyone logs on to see how big the shake was.

For each earthquake, the site shows you not only how big the earthquake was, but where its epicentre was – that’s the point on the surface of the Earth below which the earthquake occurred, and how deep it was, and it shows a really nifty map which is a vertical cross section of the Earth’s crust under New Zealand. When you look at the pattern of earthquakes on that map you can really see the Pacific plate sliding under the Australian plate and going down below us at about 45 degrees.

Q: So this is the Pacific Ring of Fire in action!

A: Yes, that’s exactly what’s going on. The Earth’s crust is being created under the Pacific Ocean, and it spreads out towards the continents around the Pacific Rim. Oceanic crust is thinner and denser than continental crust, so at the edge of the Pacific the oceanic crust dives down below the continental crust. That’s where you get earthquakes and volcanos as one plate goes down below the other.

Q: What happens to the plate that goes down?

A: I guess it ultimately melts in the heat under the crust and gets recycled, in geological time anyway. There’s some evidence for this kind of thing – there’s a volcano in Africa that erupts white lava that has the same chemical makeup as limestone. Scientists think it is effectively recycling a melted former ocean floor.

Q: So there’s earthquakes and volcanos on the GeoNet website – anything else?

A: Tons of data of interest to scientists around the world. That helps us get a better handle on the way the world works and on volcanos and earthquakes in general. But also the website has material about tsunamis and about landslides. I didn’t know, for instance, that there’s a slow landslide going in Taihape. Apparently land containing over two hundred houses and school is moving, slowly, and has been for years. You can look at the whole thing on the web site.

The Geonet web site is built using free software by some very enthusiastic programmers and scientists in GNS. The whole site has to be sized to handle large loads when everybody checks it after an earthquake, or when Ruapehu has an eruption. It does remarkably well. I think the taxpayer has got excellent value for it.

There are some great resources about volcanos and earthquakes online in overseas sites as well. The US Geological Survey site covers the whole world, although it has a US focus as you’d expect. It’s a site that’s well worth exploring if you have any interest.

Apple Mac users might be interested in a desktop widget – you have to be running OS 10.4 for this – called Tremor Skimmer. Tremor Skimmer gives a list of the latest earthquakes anywhere in the world, and even announces them to you while you are working of that’s what you want. That’s in the links for today’s programme.

And I’ve put up a link to a site about Vesuvius, the volcano that destroyed Pompeii. We know so much about that eruption because it was written about in detail by Roman historian Pliny the Younger, and of course because of the excavations of the destroyed Roman towns of Pompeii and Herculaneum. Vesuvius is very active still, and there are now two million people living around it.

Q: So what are we meant to do if a volcano goes off more seriously here, say in Auckland?

A: There’s the government’s Get Thru site that its been ballyhooing on TV ads. I checked it out and I have to say I found it devoid of any useful information. Sure, it tells you to have canned food in your house, but that’s about it. The site has only a few PDFs of brochures under its “Resources” heading and when you click “Latest News” you get taken to the Ministry of Civil Defence site. That’s OK, but then clicking on the Ruapehu page takes you to something about the lahar last March! I really think the government ought to be trying a bit harder to provide a sensible site that integrates advice with up to date hazard information.

So, nine and a half out of ten for GeoNet, and no better than four for Get Thru.


As always, you can discuss this broadcast at

Saturday 29th is E-Day: recycle those old computers and telephones.

GeoNet, the volcano and earthquake monitoring site from GNS.

The US Geological Survey’s volcano page and its earthquake page.

Tremor Skimmer, a Mac OS widget that displays the latest earthquake anywhere in the world.

A website about Vesuvius, the Italian volcano that destroyed Pompeii. It’s still active, and has about 2 million people living around it.

A fascinating book about the surface of our planet and how it changes over geological time periods.

The Government’s Get Thru website containing useful advice about civil defence.

posted by colin at 11:50 am  


  1. Hi there

    The link to the ‘fascinating book’ is not working (I’m using Safari on OS 10.4.10 and getting a “Sorry, an error prevented the CARLweb client from connecting to the state server. Please click here to try again.” message.

    Can you please provide the book details in bibliographical form? Sorry I can’t remember the author or title after hearing your discussion today.

    Many thanks!

    Comment by Andrew — 27 September 2007 @ 10:27 pm

  2. Sorry about that!

    The book I referred to is The Earth by Richard Fortey.

    # Paperback: 448 pages
    # Publisher: Vintage (November 8, 2005)
    # Language: English
    # ISBN-10: 0375706208
    # ISBN-13: 978-0375706202

    — Colin

    Comment by colin — 28 September 2007 @ 7:13 am

  3. Cheers :)

    Comment by Andrew — 28 September 2007 @ 6:14 pm

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