Natural Hazards

The Changing Height of Mount Cook

Mount Cook  rock avalanche 1991. Lloyd Homer, GNS Science On 14th  December 1991 a massive rock avalanche occurred from the East Face of Aoraki /Mount Cook, sending an estimated 14 million cubic metres of rock in a 1.5 kilometre wide cascade across the grand plateau and down onto the Tasman Glacier. It is thought that the avalanche travelled at speeds of 400 to 600 km per hour, and the resulting seismic recording at Twizel, 75 km away, lasted well over a minute, registering the equivalent of a magnitude 3.9 earthquake. Mt Cook Dec. 1991.  M. McSaveney, GNS Science Prior to the avalanche the surveyed height of New Zealand’s highest peak was 3764m. The Department of Survey and Land Information (now LINZ) calculated that this was reduced by 10 metres after the summit fell off with the rock fall. As you can see from the photo, the peak became extremely narrow and unstable. In the image taken by GNS geomorphologist Mauri McSaveney a few days after the event. A lone climber that can be seen as a tiny dot inside the red circle  gives some idea of the scale. The “new” summit was obviously highly unstable, and would be subject to quite rapid erosion following the rockfall. Since 1991, there has been no re-calculation of the revised elevation of 3754m until recently. At the end of November 2013, I flew up to Plateau Hut with a climbing team who planned to take direct GPS measurements of the summit ridge of the mountain, a short distance from and a few metres below the highest point. The measurement would then be used to validate a computer model made from recent aerial photos to give a precise calculation of the present height of the peak itself. The team was made up of (left to right): Geoff Wayatt, mountain guide; Nicolas Cullen from Otago University; Brian Weedon, mountain guide; Pascal Sirguey (project leader) from the National School of Surveying at the University of Otago; Jim Anderson from Survey Waitaki and myself. Geoff, Brian, Nicolas and Jim made up the climbing team. GNS Science provided support in terms of the helicopter flights.  I was able to accompany the team to Plateau Hut where I spent two days gathering a visual record whilst they were involved in their climb. Mount Cook East Face   Julian Thomson, GNS Science The plateau of Mount Cook is arguably the most spectacular alpine setting in New Zealand. This image shows the 1500m high East Face of Mount Cook in the early morning light seen from Plateau Hut. The normal route up the mountain follows the Linda Glacier, starting on the right hand side of the image and following into the shadow behind the long low angled rock ridge (Bowie Ridge) up to the summit rocks. As well as Mount Cook itself, the Grand Plateau has views of many other summits along the main divide, including Silberhorn, Tasman and Dixon. This image shows the top section of Syme Ridge on Mount Tasman. There are three climbers just visible on the ridge just above the centre of the photo, about 10 hours into their climb from the hut. This image shows the patterns of crevasses on the grand plateau, just above the Hochstetter Icefall. Plateau Hut at night.  Julian Thomson, GNS Science The climbing party left Plateau Hut just after midnight with clear, cold weather conditions that were perfect for the climb. Mt Cook Summit Rocks, Photo Geoff Wayatt Aoraki / Mount Cook is a challenging peak to climb, with very dynamic glaciers and steep rock and ice faces to negotiate. In this photo, the climbers are in the ice gullies that run through the summit rocks. Photo Nicolas Cullen View from the summit, with Mount Tasman in the background Photo Nicolas Cullen Looking along the summit ridge of Aoraki / Mount Cook, with the two GPS units in place. The very highest point is about 45 metres distant. The GPS units measured a height of 3719 metres at their position. This measurement was consistent with the height from the computer model which then allowed the height of the high peak to be calculated as 3724 metres above mean sea level. This means that Aoraki / Mount Cook is a full 30 metres lower than the 1991 estimate of its height, showing that the mountain peak has continued to erode significantly during the last 22 years. There is more information about the project at the Otago University School of Surveying website. Here is our video of the expedition : Mountaineers staying at Plateau Hut can get an incredible 360 view of the surroundings from nearby glacier dome. We have even created a GeoTrip for the location:  www.geotrips.org.nz/trip.html?id=450

The Changing Height of Mount Cook Read More »

Earthquake impacts in Marlborough seen from the air

Dougal Townsend of GNS Science was part of a team that flew over Marlborough to assess the impact of the recent earthquakes on the landscape and infrastructure. Although relatively minor compared to those that impacted the Christchurch area in 2010 and 2011, there were nonetheless some isolated, but significant effects. All these photos were taken by Dougal: Here you can see damage (cracking) to State Highway 1 between Seddon and Ward (near Caseys Road turnoff) following the Lake Grassmere Earthquake. Large landslide in the Flaxbourne River catchment (about 8.5 km west of Ward). Another Large landslide. This is  in Miocene mudstone, just south of Cape Campbell. A whole section of the hillside has slipped Bell’s dam near Seddon. Damage (cracking) was sustained during the Cook Strait Earthquake and was exacerbated during subsequent aftershocks and also during the Lake Grassmere Earthquake. The channel was dug to partially drain the dam, to lessen potential flood risk to the town of Seddon, which is 10 km downstream to the NE. A closer view of the cracks along the top of Bell’s dam. alongside the vehicle track This image shows rock fall on a farm track about 2 km southeast of Ward (track goes up to Weld Cone). The rock is Late Cretaceous sandstone and siltstone.  Ground damage in Needles Creek, west of Ward. Cracking of the farm track (centre left) is from the Lake Grassmere Earthquake, whereas the minor landsliding of the terrace gravels on the right may be from a combination of storm (rainfall) and earthquake (ground shaking) damage. 

Earthquake impacts in Marlborough seen from the air Read More »

Lake Grassmere Quakes

Following the earthquakes in southern cook straight, the GeoNet rapid response team left immediately to place seismometers around the area, to allow more detailed monitoring and get better information with which to model the fault ruptures. This meant that when the Mag 6.6 occurred, the enhanced array of seismometers was already in place. Here is a screen shot of the Mag 6.6 Grassmere Earthquake and immediate aftershocks over the following hours: This GeoNet video gives an idea of the number and locations of aftershocks from the 16th to19th August

Lake Grassmere Quakes Read More »

Earthquakes in Southern Cook Strait

This is a screen shot of the Wellington seismometer from very early on Monday morning 22 July Following the earthquakes in Cook Strait over the weekend, it was impressive to arrive at work on Monday morning, and watch how the GeoNet team, many of whom had been busy right through the weekend, were in full action mode again. Ken Gledhill, the head of GeoNet, co-ordinated two meetings of the scientists and technicians during the day. There are lots of different things involved with understanding earthquakes. These include getting accurate locations and magnitudes, modelling the position and orientation of the fault and the type of fault rupture from the seismic wave patterns of the aftershocks, working out the adjusted stress on nearby active faults and then trying to calculate probabilities of future quakes to inform an ‘awakened’ public… Here is the aftershock map from Sunday evening that shows the relative magnitudes of the quakes and their initial locations in 2 dimensions. Up to today there have been nearly one thousand aftershocks already. As more and more occur and get analysed, a more precise 3D image of the fault(s) involved will be built up. To help get more precise seismic data, the GeoNet fast response team are already in Marlborough, setting up some extra temporary seismometers at carefully chosen locations to ‘fill in the gaps’ between existing permanent stations. Here is a photo of one of the team yesterday, packing one of the seismometers for the trip. To see more photos of what these guys do, have a look here. This is a computer simulation of the seismic waves from the M6.5 ‘quake propagating across the North Island and the adjacent sea floor: New Zealand’s background risk of earthquake probabilities has been calculated for the whole country. Once a reasonably large earthquake has occurred, these background risks of a larger quake increase for a while in the local area, and  a sequence of aftershocks follows that typically fits into a fairly predictable pattern of decreasing intensity over time. In the video below Matt Gerstenberger explains how these calculations are made to produce probability tables and maps for future aftershocks. For the latest information about the number and magnitude of aftershocks that have occurred in Cook Strait, as well as forecast probabilities for future quakes, have a look at this GeoNet page

Earthquakes in Southern Cook Strait Read More »

Volcano Gas Flights Video

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

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 »

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.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 »

NZ ShakeOut – why all New Zealanders should participate

GNS Science is very proud to support the NZ ShakeOut earthquake drill on September 26th. Watch the video if you don’t already realise why being aware and prepared for an earthquake is a good idea. The event, which will run right across the country at 9.26am, will prompt all of us to check our plans and  preparations against the possibility of a damaging earthquake. New Zealand ShakeOut has been created to help people and organisations get better prepared for major earthquakes, and practice how to be protected when they happen. Everyone will practice “Drop, Cover and Hold”—the right action to take in an earthquake. If you haven’t already registered, help the ShakeOut reach over 1 000 000 participants by clicking here

NZ ShakeOut – why all New Zealanders should participate Read More »

“Drop, cover and hold on” is the best advice…

How to Respond to an Earthquake in New Zealand This article has been compiled by Karen Hayes at GNS Science with the help of experts including Julia Becker and David Johnston from the Joint Centre for Disaster Research at Massey University, and Adrian Prowse from the Ministry of Civil Defence and Emergency Management (now the National Emergency Management Authority). All photos are by Julian Thomson.  Information about the ‘Triangle of Life’ has been disseminated via a chain e-mail that has been in circulation since the 1990’s. The claims regarding the “Triangle of Life” earthquake response are widely discounted. The “Triangle of Life” is not an advocated approach to responding to earthquakes and has been internationally dispelled as being unsound practice. In modern countries such as New Zealand, most buildings are constructed well and you are more at risk of getting hurt from objects flying around rooms. Therefore people should “drop, cover and hold on” in an earthquake. The New Zealand Ministry of Civil Defence and Emergency Management includes the recommended “drop, cover and hold on” advice on their webpage that you can download:  I recommend you print the fact sheet and stick it on your fridge to remind yourself and your family of how best to respond in an earthquake.    Let’s just take a quick moment to consider one of the claims in the “Triangle of Life” chain e-mail. It states that children have been killed in past earthquakes because they were under their school desks and these were flattened when the building collapsed. It states that they would have been safe had they been lying beside the desk, instead of under it, where a supposed ‘void space’ should be. Realistically speaking, if the desk was not substantial enough to protect the child under it and was flattened by the collapse of a building, then any void space wouldn’t have been large enough to protect the child lying on the floor next to it either. A child is better off getting under the desk to prevent them from being struck by falling items. In the Christchurch earthquake on 22 February 2011, when children did “drop, cover and hold on” under desks, there were no significant injuries reported from any school in the Christchurch area. Building codes designed to reduce earthquake risk will ensure that buildings are unlikely to collapse in the first place. Why Rescuers and Experts Recommend Drop, Cover, and Hold On (the following is taken directly from the earthquakecountry website) Trying to move during shaking puts you at risk: Earthquakes occur without warning and may be so violent that you cannot run or crawl; you therefore will most likely be knocked to the ground where you happen to be. On that basis, it is best to drop before the earthquake drops you, and find nearby shelter or use your arms and hands to protect your head and neck. “Drop, cover, and hold on” gives you the best overall chance of quickly protecting yourself during an earthquake… even during quakes that cause furniture to move about rooms and even in buildings that might ultimately collapse. The greatest danger is from falling and flying objects: Studies of injuries and deaths caused by earthquakes over the last several decades show that you are much more likely to be injured by falling or flying objects (TVs, lamps, glass, bookcases, falling masonry, etc) than to die in a collapsed building. “Drop, cover, and hold on” (as described above) will protect you from most of these injuries. If there is no furniture nearby, you can still reduce the chance of injury from falling objects by getting down next to an interior wall and covering your head and neck with your arms (exterior walls are more likely to collapse and have windows that may break). If you are in bed, the best thing is to stay there and cover your head with a pillow. Studies of injuries in earthquakes show that people who moved from their beds would not have been injured had they remained in bed. You can also reduce your chance of injury or damage to your belongings by securing them in the first place. Secure top heavy furniture to walls with flexible straps. Use earthquake putty or velcro fasteners for objects on tables, shelves, or other furniture. Install safety latches on cabinets to keep them closed.   Building collapse is less of a danger: While images of collapsed structures in earthquakes around the world are frightening and get the most media attention, most buildings do not collapse at all and few collapse completely. In earthquake-prone areas of New Zealand, as in many other countries, strict building codes have worked to greatly reduce the potential of structure collapse. However, there is the possibility of structural failure in certain building types, especially unreinforced masonry (brick buildings) and in certain structures constructed before the latest building codes. Rescue professionals are trained to understand how these structures collapse in order to identify potential locations of survivors within “survivable void spaces”. The main goal of “drop, cover, and hold on” is to protect you from falling and flying debris and other non-structural hazards, and to increase the chance of your ending up in a “survivable void space” if the building actually collapses. The space under a sturdy table or desk is likely to remain even if the building collapses – pictures from around the world show tables and desks standing with rubble all around them and even holding up floors that have collapsed. Experienced rescuers agree that successfully predicting other safe locations in advance is nearly impossible as where these voids will be depends on the direction of the shaking and many other factors. If you receive the email in future…If you receive the “Triangle of Life” email, you should reply to the sender and let them know the advice is wrong, and point them in the direction of correct information about how and why to “drop cover and hold on”! Summary:     Do: • Identify safe places at home and

“Drop, cover and hold on” is the best advice… Read More »

Where was that earthquake and how big was it?

We have a new GNS Science video today that explains how scientists locate the source of an earthquake and then calculate the magnitude. John Ristau, from GNS Science’s GeoNet programme talks through the steps of the process… And in case you missed this earlier video, here is Matt Gerstenberger, describing how earthquake forecasts are made using statistics derived from global aftershock sequences:

Where was that earthquake and how big was it? Read More »