If you had to work out the daily quantities of different gases coming out of a volcano and spreading across the sky in a huge, mostly invisible plume, where would you begin? This video gives a brief introduction to how New Zealand’s GeoNet scientists go about it: The information is combined with other evidence such as seismic monitoring to judge the risk of future volcanic eruptions.
Volcano Gas Flights Video Read More »
Yesterday I joined Karen Britten on a GeoNet gas monitoring flight over White Island. This was to check the flux of volcanic gas emissions following an ash eruption a few days ago.Check this GeoTrip page if you are interested to visit White Island / Whakaari yourself: www.geotrips.org.nz/trip.html?id=541 ) The plane is modified to allow the equipment to extend outside so that the measurements can be made. carbon dioxide (CO2), hydrogen sulphide (H2S) and sulphur dioxide (SO2) are the most common volcanic gases and are all measured during a gas flight. Approaching White Island, we could see the plume extending first vertically, then off to the West at an altitude of about 2 000 feet. In the distance you can see a grey haze in the sky which is the extension of the plume. Our first task was to fly in circles at constant (neutral) throttle. Through using our GPS to measure our ground speed, we could calculate the effect of the wind on the plane, and thus work out the wind direction and velocity. The track of the plane is visible on the computer screen. Next we flew under the plume at right angles to the wind direction and at the lowest permissible altitude of 200 feet. A Correlation Spectrometer (COSPEC) looks upwards through the plume and measures the amount of ultra violet light being absorbed by the sulphur dioxide. We passed under the plume several times in order to get an average reading. The wind speed is also taken into account to calculate the SO2 flux with this method. Next we flew in wide arcs through the plume, at a radius of about 3 kilometres from the crater. We worked our way contouring back and forth, rising 200 feet each time to get a total profile of the gases through the whole plume. Later in the day Karen was able to process the data to show that the daily flux of SO2 was about 600 tonnes. This is at a relatively elevated level compared to mid January, but has not changed much in the last month. Here are the complete data that Karen processed after the flight, comparing them also to the two previous gas flights: Lastly we flew close to the main crater to get a look at the changes that had occurred in recent days. Most of the gas emission was coming from a small crater or tuff cone, and there seemed to be an area of red brown which is probably ash from the recent eruption. Back in Taupo after a total flight time of about 4 hours, I had this evening view across the lake to Tongariro. The Te Maari crater was producing a thin plume of its own extending across the sunset.
White Island Gas Flight Read More »
See the video of our visit to White Island: Here’s a bit more about what we did during our day on there: Karen and Agnes set off with their water monitoring equipment, whilst Brad, Steve and I started the elevation survey, measuring height differences between an extended series of fixed points that had been marked by wooden stakes driven into the ground. Whilst Steve held the survey pole, Brad aimed his leveler at it from an adjacent measurement station and was able to read off the height difference between the two points. By sighting between the points in this way, we continued our survey past some very loud and active fumaroles, in a broad area towards the crater lake. Occasionally we stopped to take photographs of interesting features, or discuss the history of the formations around us. Once or twice we were enveloped in steam and gas from the fumaroles, and rained on by acidic water droplets (acid rain) that gave a burning, prickling sensation to my eyes. Past measurements have shown that the ground near the crater has been rising by two or three centimeters every three months for several years, mainly due to an increase in heat in the ground. From our measurements we found that the hottest area of ground near the most active fumaroles had risen up to a maximum of 50mm since the last survey, with the amount of uplift reducing quickly a short distance away. These results show continuity with the long term trend of uplift. Almost towards the end of the survey, we met up with Karen and Agnes, and I watched them sampling the water from a very active hydrothermal spring that was gushing and splashing nearby. To make a variety of measurements of the water chemistry and isotopes, they scooped water out of the spring and put it into various sampling bottles. Once our survey was done, Brad and I walked over to the lower of two webcams to give the glass a wipe, as the photos had been getting quite fuzzy due to a build up of dust. There in front of the camera was ‘Dino’ in real life. He is a small dinosaur, apparently famous the world over for having arrived mysteriously to take up residence in full view of White Island’s Crater Webcam some years ago: see http://www.geonet.org.nz/volcano/activity/white-island/cameras/whiteisland-latest.html Before we returned to the helicopter, we walked through the ruins of the old sulphur mine, where there were rusted machines and derelict buildings. Finally we were ready to leave and as we turned in a wide loop above White Island, I was very impressed to have been able to have had such a close encounter with such a remarkable place.