White Island Gas Flight

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.

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.

Saddle Cone

On my way back to civilisation from Tama Lakes, I decided to take a detour to visit Saddle Cone, a small isolated crater on the northern slopes of Ruapehu. You can see the tilted rim of the cone in the centre of the photo:

The second image is looking into the crater of Saddle Cone, which is about 100 metres across.
In spite of its small dimensions, Saddle Cone produced a huge lava field that spreads out over an area of several square kilometres. These lava flows are visible in the distance.

On the right side of this photo you can see a moraine ridge, showing that this valley was glaciated until about 10 000 years ago. This provides a maximum age for these lava flows, and many others in Tongariro National Park's glaciated valleys.

Hot arid summers, and freezing blizzards in winter are not too much for hardy alpine plants such as these:

After several hours of wandering the semi-desert of the Tama Saddle, I descended to a river less than an hour from the road - a perfect oasis to end my hike on the mountain.

Ngauruhoe's Far Side

Climbing Ngauruhoe from the South is well off the tourist route, and involves scrambling up unstable blocks of lava for about 700 vertical metres up the face of the cone.

I chose to go up more or less up the centre of the view you can see here, and it took me about an hour and a half of steady plodding to the top.

The crater of Ngauruhoe was last erupting from 1973 to 1975, during which time it occasionally threw out blocks of lava to a distance of about 3 kilometres. If you click on the image to enlarge it you will see people on the crater rim that give an idea of the scale of the image.

Ngauruhoe's crater rim provides what to me is one of New Zealand's finest landscape views. On the far left is Tongariro peak, then the flat top of North Crater and the Blue Lake (with steam from Te Maari just behind it). Just below the Blue Lake is the top of Red Crater and on the right side are old lava flows in the Oturere Valley. The Tongariro crossing track passes through South Crater as a white line in the centre of the photo.

Descending the northern slope of Ngauruhoe, I then climbed a rocky ridge up to Tongariro peak, seen running from the centre to the right side of this photo:

Next on my route was Red Crater, followed by a swift run down grey coloured soft scree just visible on the right of the photo. This took me into the Oturere Valley from where I turned back in the direction of my campsite.

In the area to the east of Ngauruhoe I cut across country around the base of the volcano. This is a relatively rarely explored area. It took me a few more hours tramping across a variety of moraine ridges and blocky lava flows to reach my tent after a very satisfying day.

Tama Lakes

Last weekend I went to camp and tramp in the Tama Lakes area on the saddle between Ruapehu and Ngauruhoe.

These lakes were created by several explosion craters within the last ten thousand years  giving them a circular or crescent form. The landscape is covered with blocks of lava and scoria as well as some fine ash  remaining from Ruapehu's 1995 - 1996 eruptions.

There are also some layers of pumice from the huge Taupo eruption about 1800 years ago. This photo shows some charcoal fragments - remains of some of the vegetation that was scorched during the most violent eruption on earth in the last 5000 years.






The lower Tama lake is being slowly filled up by a river bringing in eroded ash and other volcanic debris from the surrounding area. You can see this delta on the far side of the lake in the image. Beyond it is a similar adjacent (sediment filled) crater of about the same size. The water is very clean and drinkable, and yes - it really was that blue!

I set up my tent in a little hollow, sheltered from the wind and on a nice flat spot.

The view north from my campsite shows the Upper Tama lake and the south face of Ngauruhoe, my planned hike for the next day.