Ruapehu

Lahars on Ruapehu

Leave a Comment / Earth Science, Julian's Blog / / , , ,

Ruapehu Eruption, Image: Lloyd Homer@GNS Science Ruapehu is very popular with skiers, trampers and other adventurers. As an active volcano with the potential for sudden eruptions through its crater lake, Ruapehu presents the Department of Conservation with a significant hazard management issue. Lahars on Ruapehu: Image: Lloyd Homer@GNS Science Obviously there is the possibility of people in the vicinity of the summit area being immediately affected by water, rocks and ash thrown out by an eruption. An additional hazard is that displaced water and sediment from the crater lake can mix with snow and loose volcanic material to create fast moving mudflows (lahars) which descend rapidly down valleys radiating away from the summit. The collapse of the crater wall can also cause a lahar to flow down the Whangaehu Valley to the east of Ruapehu, independently of an eruption. It was this type of lahar that caused the railway tragedy at Tangiwai in 1953. This video explains the basics of lahars at Ruapehu and the two ways they can be created: Image Graham Leonard@GNS Science Not surprisingly, due to the high number of mountain users, the lahar hazard has been studied in detail and measures put in place to give warnings and reduce the potential impact on people and infrastructure. This has involved a close collaboration between GNS Science (GeoNet), the Department of Conservation and Ruapehu Alpine Lifts who run the ski areas. First of all, regular monitoring of the crater lake’s physical and chemical properties is carried out by GNS volcanologists as part of the GeoNet project. This alerts them to changes of activity within the volcano: This information helps the GeoNet team to set the volcanic alert level for the mountain, which is important for a number of agencies such as the air industry, Regional Councils, local businesses and others. Because of the potential for some eruptions to occur with little or no warning, and the speed with which lahars travel down the slopes, there is also an Eruption Detection System (EDS) in place. This is triggered when both ground-shaking (seismic waves) and an air blast are detected within a short time of each other at a number of monitoring stations throughout the Tongariro National Park. This image shows the arrivals of volcanic earthquake tremors (top) and the air blast (bottom) of an eruption, at a station about 9 kilometres from the crater lake: You can see that there is a time lag of about 30 seconds between the onset of groundshaking and the arrival of the air blast at the same station. The EDS system has been developed by GeoNet and is unique in the world. A detected volcanic eruption will automatically set off the Lahar Warning System, consisting of loudspeakers that warn people in the ski areas to get out of valleys that could be affected, and onto high ground nearby. This video describes the system that has been set up to protect skiers on the mountain and how it is tested for its effectiveness: There is also a lot of information displayed visibly at key points in the ski areas and surrounding facilities and communities to explain the lahar hazard, and what to do or not to do if a warning alarm is sounded:

Lahars on Ruapehu Read More »

Volcano Gas Flights Video

Leave a Comment / Earth Science, Julian's Blog / / , , , , , ,

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 »

Flight over Tongariro and Ruapehu

Leave a Comment / Earth Science, Julian's Blog / / , , , , ,

My next experience of a GeoNet gas monitoring flight was over Tongariro and Ruapehu. This time Karen Britten and I were joined by Fiona Atkinson (left in photo) who is part of the GeoNet volcano monitoring team. As we approached the volcanoes from over Lake Taupo, the small gas plume from Te Maari was visible. Because the plume is quite low against the mountain side, GeoNet cannot always monitor it by plane. They sometimes use a road vehicle instead, traversing under the plume along a nearby road.Our flight took us past the Red Crater (left) and the Emerald Lakes, where I had been tramping a few days before. North Crater on the right skyline is a solidified lava lake, whilst the dark lava flow in the middle distance on the right originated out of Red Crater. We circled Ngauruhoe several times just in case there was some evidence of gas emission, although non could be determined. If you click on the photo to enlarge it you can just see some people on the left hand side of the inner crater rim. The crater lake of Ruapehu was a uniform pale blue colour, with no visible upwellings. Our gas measurements showed about 670 tonnes per day of CO2 , a little H2S (0.5 t/day) and about 28 tonnes per day of SO2. These figures are in a similar range to those from the end of January, but somewhat elevated compared to December. On the way back we decided to take a closer look at the Upper Te Maari crater area. There is still a lot of grey ash covering the area from the November 21st eruption, and yellow sulphur deposits around the fumeroles. Having landed back in Taupo, I drove down to Whakapapa Village, and was able to look at the Te Maari area from the road on the way. The area affected by ash can be seen extending across the mountain side.I decided that I just had time at the end of the day to walk up Te Heuheu peak on Ruapehu. It is on  the north edge of the summit plateau.  The crater lake is just beyond the sunlit snow in the centre of the photo, out of sight behind the ridgeIn case you haven’t seen in yet, here is a video of the Te Maari eruption made from the webcam shots on November 21st:

Flight over Tongariro and Ruapehu Read More »

Saddle Cone

Leave a Comment / Earth Science, Julian's Blog / / , , ,

On my way back to civilisation from Tama Lakes, I decided to take a detour to visit Saddle Cone, ( GeoTrip page here: www.geotrips.org.nz/trip.html?id=53 ) 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.

Saddle Cone Read More »

Tama Lakes

Leave a Comment / Earth Science, Julian's Blog, NZ Geology Sites / / , , ,

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.

Tama Lakes Read More »

Filming on Ruapehu

Leave a Comment / Earth Science, Julian's Blog / / , , ,

Last week I spent some time on Ruapehu with Bruno Cedat, a french documentary maker who is making a film about the geology and landscapes of New Zealand in collaboration with GNS Science. During the making of his film he has participated in challenging outdoor adventures such as climbing, caving and kayaking in a variety of wild places across New Zealand, Here he is climbing the Pinnacles next to Whakapapa ski field. We also tramped up the mountain to the summit plateau, with great views across to Ngauruhoe volcano further north. In this next picture you can see Bruno approaching the Dome, along the edge of the summit plateau.   The Dome Shelter was covered in rime ice. Inside the shelter there is a seismometer that is used to monitor volcanic earthquakes. Here is the GeoTrip page for you to climb up to the Dome: www.geotrips.org.nz/trip.html?id=646 Here is a view of the crater lake, surrounded by a winter blanket of snow. It is currently at Alert Level 1 as you can see on the GeoNet website. For  lots more information on Ruapehu have a look at our website here Here is a preview of Bruno’s Film: New Zealand, Land of Adventure:

Filming on Ruapehu Read More »