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In September 2014 a ‘target’ was established on the top of Donald Mound at White Island that was large enough to be seen in the web camera images. This gave the GeoNet volcano team a reference point on the web camera images and from this we were able to track the water level in the Crater Lake.  We were able to track over 5 metres of water level change before it was destroyed by the 27 April 2016 eruption.

This week we have established a new target on the crater rim, so we can start following the water level changes in the new lake, which is now forming on the crater floor.   The Crater Lake(s) at White Island have had quite a history of change since the first major lake started to form in 2003. From mid-2003 to early 2006 the water level rose about 26 metres, getting to within 2 meters of overflow. The lake then fell to be about 23 meters lower by mid-2007. During this time the lake was heating, so it was basically being evaporated away. It refilled to about 7 metres below overflow by early 2009 and stayed there until heating started in late 2010. The lake again evaporated away. Small eruptions followed in August and October 2013.

The lake started to reform in November 2013. From December 2013 to May 2014 the lake rose about 3 metres and then remained unchanged until June 2015. Then the water level rose another 2 metres before again starting to evaporate away in March 2016, falling over 2 metres before the 27 April eruption. Conditions are now stable enough for us to start monitoring the water level again via the web camera images. The Crater Lake temperature is now 60 °C and the water level about 31 m below overflow.

Volcanic Alert Bulletin RUA 2016/08:
1:00pm Monday 15 August 2016; Ruapehu Volcano

Alert Status:
Volcanic Alert Level remains at Level 1
Aviation Colour Code remains Green

Last week a Crater Lake sampling and gas flight were completed by GeoNet staff at Mt Ruapehu. Observations and data from these activities confirm the Crater Lake is still cooling, but at a slower rate and there is volcanic gas passing through the lake. The temperature of the summit Crater Lake is now 13 ºC. The observations from the gas flight and sampling indicate the vent(s) on the lake floor are open, allowing gas, steam and water to vent into the lake. These are typical conditions for Mt Ruapehu.

The volcanic alert level for Mt Ruapehu remains at Volcanic Alert Level 1 (minor volcanic unrest). The Aviation Colour Code also remains unchanged at Green.

The gas flight completed on August 10 recorded the volcanic gas at levels typical of low-background output for Mt Ruapehu. Convection was noted in the lake. On August 11 a Crater Lake sampling for gas and water was also completed. Up welling was again obvious in the lake and was outlined by sulphur slicks, which are frequently seen when the lake is convecting. The lake was a dark green-grey colour and was overflowing. There was a fairly strong sulphur smell near the lake. The lake temperature was measured at 12.6 ºC, consistent with the data logger observations. Today the data logger reports a temperature of 12.9 ºC.

The level of volcanic tremor which was elevated to moderate levels in May-June has declined and is now at typical background levels. Data available at present indicates the level of volcanic unrest at Mt Ruapehu is low.

GNS Science continues to closely monitor Mt Ruapehu  and our other active volcanoes through the GeoNet project. The Volcanic Alert Level ranges from 0 to 5 and defines the current status at a volcano. Aviation Colour Codes are based on four colours and are intended for reference only in the international civil aviation community.

 

Steve Sherburn
Duty Volcanologist

 

Media Contact:
Brad Scott
Phone 07 3748211

The active vent-crater at Mt Ruapehu is occupied by a crater lake. This summit Crater Lake displays temperatures that typically range between about 15 and 40 °C. This has been a common feature of the Crater Lake since the mid 1960’s. The lake took several years to refill and become established following the 1995 and 1996 eruptions. GeoNet obtains temperatures from the lake using a data logger with a temperature sensor in the lake and communications via a satellite link.

Since May the temperature of the Crater Lake has been declining and continues to do so. The lake is now 13.5 °C and has been cooling at about 0.5 °C per day. In August 2014 the temperature was just under 15 °C, the lowest since the 1995/1996 eruptions. Now the lake is cooler by about 1°C. We have measured cooler temperatures more than 10 times in the 1980’s and 90’s. Cool lake temperatures are not that unusual. The heating and cooling cycles are controlled by a mix of volcano and geothermal processes. The heat flow into the volcano from the hot and sometimes molten rock under it just gets turned on and off, like a tap. Then the lake heats or cools and maybe sets a new record.

On 11 May 2016 the lake reached a high of 46°C, the highest we have observed since it reformed in 1999-2000. This high temperature was also accompanied by volcanic tremor and an increase in the output of volcanic gas. The Volcanic Alert Level (VAL) was raised to Level 2 at that time, lowering to Level 1 in early July when the gas output and volcanic tremor levels declined.

During the last 50 or so years Mt Ruapehu has erupted often and one trend we have noticed is that the eruptions occur from a hot lake. However we have also noted a few from a cold lake. They do not occur every time the lake gets hot or cold, however if one does occur it will more likely be at one of these extremes. This becomes a time when we pay some extra attention to the status of the volcano.   Further sampling and visits to the Crater Lake are planned as the weather allows, being part of the standard GeoNet monitoring programme for Mt Ruapehu.

In the 15 years since GeoNet started a lot of work has been undertaken on the networks. This has ranged across the sensors, digitizers, communications links, out stations and optimization of the data collection and archive. These have been focused across the whole project with many benefits for the volcanology team. When we started we already had many seismic dots on the map and have had a modest increase in those. However the technology behind the dots has improved so much. Fifteen years ago we had no dots on the map for the GPS, gas and acoustic sensors and remote cameras. Today we have multi-sensor arrays at many of the volcano sites (seismic, GPS, gas and acoustic).

Seismic Networks

During the 1990s the focus was on creating ‘volcano-seismic networks’ at each of the active volcanic centres, getting the data back to a local data recorder (digitizer). We then couriered the weekly data tapes around for subsequent analysis. The concept of a central data centre was almost non-existent. We deployed a USGS-based technology for converting the sensor signal so we could transmit it across UHF radio links and then record it. All the sensors were what is termed 1-D, in that it recorded only the vertical component of the seismic wave. Some lived down shallow bore holes (10-30 m) to reduce the local noise. Two of the networks were owned and operated by the local Regional Councils (Auckland and Taranaki).

The GeoNet approach was to upgrade all the sensors to 3-D (vertical component plus two horizontal components), install digitizers on site (with backup memory) and use digital communication systems to move the data around. We also added in some new sites to improve cover or create cover where we didn’t have any. This was an enormous step forward in data quality and quantity. This was followed by an evaluation of the data quality, leading to several sites being placed in deep drill holes to improve data quality. Some of the holes are 200-300 m deep, especially in Auckland where there is a lot of ‘cultural noise’ made by the city - and we are interested in the area under the city! All of the volcano sites are now part of the New Zealand network.

 

GPS Network

In the early 1990s we had started to use GPS receivers in collaboration with international research teams to measure ground deformation on a regional scale around the volcanoes and elsewhere in New Zealand; we didn’t have any permanent sites. With the advent of GeoNet we were able to start creating a GPS network with permanent recorders on or near the volcanoes. We had two goals with our first networks: to record the regional deformation, and that local to the volcano centres. Some of the sites form lines across the volcanic zone, while others focus on the volcano, especially the caldera volcanoes. The volcano sites are also an integral part of the New Zealand-wide network.

 

Acoustic

When you're unable to see the volcano it’s not so easy to confirm or deny if an eruption has occurred. We often see volcanic earthquakes that do not produce an eruption at the surface. With our changeable New Zealand weather and half the day being night, we don’t get to see them all that often. This is where acoustic sensors come in to play as they record the airwaves from the explosions. So if we have a volcanic earthquake and an airwave, then we can be pretty certain we have an eruption.

Volcanic Gas

Active volcanoes put out lots of volcanic gas, sometimes this can be thousands of tonnes per day (or tens of kg per second). The main gases are water (H2O), carbon dioxide (CO2) and sulphur dioxide (SO2). We have several techniques to measure all of these gases at the volcano, but not so many that can give us continuous data. In fact we can only get SO2 reliably at present. We have these sensors at White Island (Whakaari) and Tongariro, and under suitable conditions get data daily.

Cameras

Nothing beats getting to see the volcano. Around 2000 we started using Olympus digital cameras as remote cameras. These had a cable that could be connected to your computer and software would trigger the camera and download the photo from the camera. We then nutted out a way to do this remotely, both in Whakatane and at the Chateau, and have them transmit the pictures back to us in Taupo. Today we have thirteen cameras that collect an image every second (but we only bring back one every 10 minutes for the website). The cameras are in fact 2 cameras: a daylight one and a special low-light one for night.

 

 

In the 15 years since GeoNet was created many people have worked as a part of the Volcano Team. Several have been with us from the start, others have joined along the way, while other have come and gone. There are a few who date back to volcanology in GNS Science and three that date back to the DSIR (Dept. of Scientific and Industrial Research), which was the forerunner to GNS Science. As you will see many have worked all over the world on many varied volcanoes and have a lot of experience in how to deal with volcano crises. Skills range from building monitoring networks, to geology, geophysics, geodesy, geochemistry, social science and communications. 

Cameron Asher

In July 2001 I was still in primary school and I had no idea what GNS Science was, or what GeoNet would become, I just wanted to be a fireman. Today I'm a Volcanic Operations Technician (equally as awesome), part of a team of technicians that make sure GeoNet's monitoring equipment around New Zealand keeps providing useful information on the state of volcanoes, earthquakes and ground deformation.

Karen Britten

In July 2001 I was working for GNS Science in the geothermal lab and already involved in volcanoes and geothermal systems. Today I’m the volcano geochemistry technician for the GeoNet volcano team.

Bruce Christenson

In July 2001 I was working for GNS Science undertaking geothermal and volcano fluid research. This took me to volcanoes and geothermal systems and I was keen on the role gases play. Today I’m the Senior Volcanic Fluids Geochemist for GeoNet.

Natalia Deligne

In July 2001 when GeoNet started I had just finished my first year at university at Caltech in Los Angeles; three months before I had decided to switch my degree from astronomy to geology. A year and a half later I decided to be a volcanologist and went on to complete my masters (University of Bristol) and PhD (University of Oregon). I joined GNS Science in 2012 as a post-doc and became permanent staff in 2014. Today I'm a volcanic hazard and risk modeller, I serve as a GeoNet volcano duty officer, and am committed to doing what I can to minimise the impact of future New Zealand eruptions through monitoring and research.

 

 

Nico Fournier

In July 2001 when GeoNet started I was nearing my first year of PhD in the UK, studying how volcanoes persistently release gas for years without erupting. After working in the eastern Caribbean for 5 years as a volcanologist, I joined GNS Science in May 2009 as a volcano geodesist. Today, I head the Volcanology Department and volcano monitoring team. 

Ian Hamling

In July 2001 when GeoNet started, I had just finished my exams (GCSE's) at high school in the south-west of the UK. After more exams, a couple of degrees and a detour in Italy I arrived at GNS Science in 2013. Today I am an InSAR scientist looking at crustal deformation across New Zealand from space (satellites).

Tony Hurst

In 2001 I was at the Aso Volcanological Laboratory in Japan (visiting Professor) for a year, comparing our monitoring techniques with theirs. Before going to Japan I was experimenting with the first cell-phone connected strong motion recorders (Etnas), and was working on the first volcano-cams. Today I’m the Senior Volcano Geophysicist in GeoNet and work across many volcano problems.

Richard Johnson

In 2001 I was still at University in UK and knew nothing of GeoNet. I joined GNS Science in 2007 as an operations technician and work in the GeoNet project looking after the seismic and GPS equipment.

 

 

Art Jolly

In July 2001 when GeoNet started I was with the University of Leeds (UK) and working at Montserrat Volcano Observatory (West Indies) conducting research on seismicity of Soufriere Hills volcano. Today I’m a Senior Volcano Geophysicist with GNS Science, joined in 2006 and conduct research on volcano seismic and acoustic properties.  

Gill Jolly

In July 2001 when GeoNet started I was in Montserrat, West Indies working at the Volcano Observatory as the Director. I joined GNS Science in 2006 as a physical volcanologist. Today I'm Director of the Natural Hazards Division (and still very interested in what the volcanoes are doing!).

Geoff Kilgour

In 2001, I was studying for my MSc degree in Earth Sciences at University of Waikato. I joined GNS Science in 2002 as a Volcanology Technician and today, I am a Volcano Geologist. I study the processes responsible for generating eruptions and the surface effects once the eruption has begun. I am part of the Duty Officer team.

Agnes Mazot

In July 2001 when GeoNet started I was at Free University of Brussels, Belgium doing my PhD on the geochemistry of fluids and CO2 degassing on Indonesia volcanoes (Papandayan and Kelud volcanoes). I joined GNS Science in 2009 as a Volcanic Gas Geochemist. My role at GeoNet is to monitor gas emission from New Zealand volcanoes (White Island, Ruapehu, Ngauruhoe, Tongariro etc.), contribute to the interpretation of the geochemical data and contribute as a duty officer.

 

 

Craig Miller

In July 2001 I was working in mining and mineral exploration geophysics in Australia. I joined GeoNet in November 2002 as a Volcano Geophysicist and later became the Volcano Network Coordinator.  In this role I oversaw the modernisation and expansion of New Zealand's volcano monitoring infrastructure.  Since 2003 I have been a member of the duty team and have been involved in the response to many volcanic events.  I am currently studying for a PhD in geophysics (investigating changes in gravity fields that occur prior to and after eruptions) and will return to GeoNet/GNS Science in 2018.

Mike Rosenberg

In July 2001 when GeoNet started, I was working for GNS Science as a Volcanology Technician, working on aspects of physical volcanology (rocks and pumice). I’m currently on leave completing my PhD on geothermal field stratigraphy.

Sally Potter

In July 2001 when GeoNet started, I was in 6th form (Year 12) at Tauhara College in Taupo. I started at GNS Science in 2002 as a summer student, and went on to do my PhD at Massey University, which included reviewing New Zealand's Volcanic Alert Level system in 2014. Today I am a Hazard and Risk Management Researcher in the Social Science Department at GNS Science.

Brad Scott

In July 2001 when GeoNet started I was working for GNS Science in the volcanology section as the Volcano Monitoring Coordinator (monitoring was part of research then). I have been involved in volcanology for over 40 years (started with DSIR). I have been involved in numerous volcano crises in New Zealand and the south-west Pacific. Today I'm the volcano communication specialist for GeoNet, contribute as a duty officer, the routine volcano monitoring and outreach functions of GeoNet and GNS Science.

Steve Sherburn

In July 2001 when GeoNet started I was working for GNS Science as a Volcano Geophysicist. I was working on models of the seismic activity that may occur before a large volcanic eruption and monitoring earthquakes at geothermal systems and the active volcanoes. Today I’m a Senior Volcano Geophysicist still, with interest in earthquakes at geothermal systems and the active volcanoes and how GeoNet deals with data.

In the 15 years since GeoNet was created the Volcano team has had to deal with many ‘volcano crisis’, these range from a volcano displaying signs of elevated volcanic unrest but no eruption occurring to eruptions that produced ashfall 100’s of kilometres away. There have been 13 volcanic eruptions from six volcanoes in the last 15 years, a busy time for the GeoNet volcano team.

Working our way south we start at Monowai in the northern Kermadecs. Monowai is a submarine volcano about 380 km northeast of Raoul Island (or 1400 km northeast of Auckland) and the summit lies about 100 m below the sea surface. Volcanic earthquake activity from Monowai appears on the seismograph at Rarotonga hence we are able to follow the activity. Routine aerial patrols by the RNZAF confirm the activity. The RNZAF pass on pictures of plumes generated by the activity. Activity is regular and noted 3-10 days a month, making it one of our most active volcanoes at the moment.

Following a sequence of earthquakes that lasted several days (but stopped 3 days before) Raoul Island erupted without warning at around 8:20 in the morning of 17 March 2006. The eruption continued for around 30 minutes and created several new vents within and near Green Lake.  Scientists found no evidence for new magma associated with this eruption and believe the eruption was caused by a pulse of volcanic gas and volatiles been released from depth which accumulated beneath a sealed hydrothermal system until the pressure was great enough to blow the seal and cause the eruption. Tragically, a Department of Conservation employee was killed by this eruption. Following this eruption GeoNet worked with DOC to further enhance the monitoring programme on the island.

Large pumice rafts were identified near the Kermadec Islands in early August. Analysis of remote sensing data (satellite images) has shown that these came from a submarine eruption at Havre submarine volcano around 17-18 July 2012. Havre lies about 230 km SW of Raoul Island or 860 km NE of Auckland. The pumice extended in a north-east direction for about 280 km in late July and was reported over 600 km long later in August. Havre Seamount was confirmed as the source following a science cruise by NIWA.

50 km off the Bay of Plenty coast lies White Island (Whakaari) an iconic view as one drives along the coast. In 2011 volcanic unrest started at Whakaari, the Crater Lake started to heat and shrink. Following a rapid water level rise (27-28 July) the volcano started erupting explosively on 5 August 2012, being followed by a period of ash emission. In late November 2012 a small lava extrusion was visible. Geysering activity was common in the reforming lake during early-mid 2013. This was followed on 20 August 2013 by an explosive eruption, with more explosive eruptions on 4, 8 and 11 October. The Crater Lake re-established after this and the water level rose. The level of volcanic unrest was variable in 2014-15. On 27 April 2016 further violent explosive eruptions occurred at White Island.

 

 

Around mid-night on 6 August 2012 the upper Te Maari crater on the north side of Mt Tongariro burst back into life after 119 years of quiescence. Te Maari had experienced local earthquake activity for 4 weeks and changes in the volcanic gas output. This short period of unrest enabled some preparatory actions by responding agencies and local residents. The 6 August 2012 eruption ejected blocks over 6 km2 and a debris flow occurred down a valley to the west, with minor ashfall occurring as far away as Hawkes Bay. The debris flow changed drainage and formed ponds, which broke out later forming small lahars. A semi-circular rift had formed south of upper Te Maari Crater, containing many small vents. A further explosive eruption occurred on 21 November. Minor remobilisation floods have continued. The output of volcanic gas declined after the eruptions.

On 4 October 2006 the GeoNet monitoring equipment detected what appeared as a small volcanic eruption at Ruapehu.  It wasn’t until the weather improved 2 days later that the eruption was confirmed. A small hydrothermal eruption had occurred with the effects of the eruption been confined to the lake basin and having only minimal impact. There was evidence of wave action up to 4-5m above the lake surface; this was not high enough to flow over the tephra dam that blocked the outlet and generate a lahar at that time.

Mt Ruapehu erupted again on 25 September 2007 and produced two lahars, a moderate eruption column to about 15,000 feet, with ash fall and rock falls across the summit of the volcano. This eruption was similar to the 1969, 1975 and 1988 eruptions. It was smaller than the 1969 and 1975 events, but larger than 1988. All evidence available indicates the eruption was hydrothermal in nature. A ballistic (rock fall) apron extended north from the lake, and actually exceeded the ash fallout zone. Typically ash travels further than the heavier ballistics, however in this case the ballistic rocks were ejected with sufficient force to out-travel the lighter ash material. One lahar travelled approximately 1 km into the Whakapapa ski field, reaching half-way down the Far West T-bar to an altitude of c. 2100 m. The other snow slurry lahar travelled down the Whangaehu River, leaving a deposit c. 80 m wide and 1 - 3 m thick near the Round-The-Mountain track bridge 7 km from Crater Lake.

Not to be left out in 2006 Ngauruhoe reminded us the he is still an active volcano when a period of volcanic unrest started in May. The seismic activity around Ngauruhoe increased above the typical background level in June so the Volcanic Alert Level was raised to Level 1.  Over the next two years GeoNet recorded an average of 5 to 30 earthquakes a day close to Ngauruhoe, though the maximum daily number was as high as 80. After mid-2008 the number of earthquakes returned to a typical level of a few per week or less. This increase in earthquake activity did not necessarily mean that an eruption is imminent. The Volcanic Alert Level was lowered to Level 0 in December 2008.

 

 

Over the weekend the Tongariro National Park area was affected by south-easterly gales. This can affect some of the volcano monitoring seismic sites as the wind flows through saddles or over the volcanic cones. This is most apparent around Ngauruhoe and Mt Tongariro. Many volcanoes when active produce a signal called 'volcanic tremor'. This is a continuous or semi-continuous ground vibration which can be produced by any of: degassing, underground boiling, magma movement or ash eruptions, plus a range of other sources. Scientists often do not know the precise cause of the volcanic tremor. On the seismograms volcanic tremor can look very like wind noise, and sometimes it is difficult to distinguish the two signals using just the seismograms.

To get around this volcanologists use two display techniques called RSAM and SSAM. RSAM stands for Real-time Seismic-Amplitude Measurement. It represents the overall signal size over periods of 10 minutes. While SSAM stands for Seismic Spectral-Amplitude Measurement. It shows the relative signal size in different frequency bands. Different seismic signals have energy at different frequencies. These tools do help use differentiate the source of some common seismic signals like surf, wind, volcanic tremor and traffic.

A problem with RSAM is that it measures the overall signal size regardless of what produces the signal. If the signal is caused by volcanic tremor then RSAM is very useful. But when the wind blows strongly the RSAM value will still go up and scientists don't learn anything about the volcano, only the weather! The key is to look at RSAM and SSAM plots together. RSAM will give us a measure of the signal size and SSAM more information on the likely source of the signal.

The examples below show the effects of the gales at two of our sites; Ngauruhoe and Karewarewa.

Volcanic Alert Bulletin RUA 2016/07:
10:30am Tuesday 5 July 2016; Ruapehu Vol
cano 

Alert Status:
Volcanic Alert Level
 is Level 1 (lowered from Level 2)
Aviation Colour Code
is Green (changed from Yellow)

The moderate to high level of volcanic unrest at Mt Ruapehu is no longer present and the Volcanic Alert Level is now lowered to Volcanic Alert Level 1 (minor volcanic unrest). The gas emissions decreased and the level of volcanic tremor has also declined. The temperature of the summit Crater Lake has declined from 46 ºC (11 May) and is now at 23 ºC. The Aviation Colour Code is also changed, going from Yellow to Green.

A gas flight was completed yesterday and recorded the gas output at levels typical of background for Mt Ruapehu. The level of volcanic tremor which has been elevated to moderate levels has declined and shows now similar levels to what it was in the second half of 2015. The lake temperature measured by the outlet data logger is now 23 ºC. After reaching a high of 46 ºC on May 11 the lake started to cool to the current value of 23 ºC.

Data available at present indicates the period of elevated volcanic unrest at Mt Ruapehu is over. The volcanic alert level for Mt Ruapehu is now lowered Volcanic Alert Level 1 (minor volcanic unrest). The Aviation Colour Code is also changed from Yellow to Green.

GNS Science volcanologists continue to closely monitor Ruapehu through the GeoNet project.

Caldera volcanoes are a special type of volcano and here in New Zealand we have several examples of these. Eruptions from these volcanoes are very rare, however they can undergo periods of volcanic unrest: wake up roll over and go back to sleep. The Okataina and Taupo Volcanic Centres are regarded as some of the most active caldera systems in the world, and yet little has been done to prepare for the consequences of an unrest event. Caldera unrest, consists of earthquakes, ground deformation, geothermal changes and gas flux could occur. These phenomena can pose hazards which need to be adequately managed.

It was recognised there was a gap in advice available for local government and other agencies dealing with the effects of caldera volcanoes which lead to the formation of the Caldera Advisory Group (CAG). It has been identified that caldera unrest could last for significant periods of time (years to decades) and the effect of this would have a profound impact on the social and economic environments. The work of the CAG is to identify the major potential impacts of caldera unrest and to address each of the areas identified. Caldera unrest is also of "national interest" given the likely impacts.

To further develop the understanding of caldera unrest the CAG is host the inaugural Caldera Stakeholder Symposium in Taupo on Monday 4 July. The intention of the symposium is to provide key agencies with information on what caldera volcanoes are, their potential risks and the disruption they could pose on society (and businesses) when an unrest episode eventuates. With specialist guest speakers and tailored workshops, the symposium will provide a timely opportunity to network, share knowledge, and to gain new insights. The symposium is aimed at:

  • Planners, asset managers, emergency managers, executives and elected members from local government and other related businesses
  • Central government agencies (including emergency services)
  • Infrastructure providers (lifelines utility companies)
  • Other sector businesses/industries including insurance companies, real estate institutions, banking sector, agriculture/horticulture associations.

 If you have any questions or require any further information, please contact Sarah-Jane Edgar at Waikato Regional Council or click here to visit the CAG website or learn more about New Zealand’s active volcanoes or view a presentation on Caldera Unrest management.

Around May 17-20 the Mud Rift feature at Waimangu Geothermal area erupted. The Mud Rift is a 36 m long, 5-6 m wide and 15 m deep geothermal vent in Raupo Pond Crater, one of the craters formed in June 1886. It is an isolated area and this is the first known eruption since 1981. The Mud Rift formed in 1906 and was last active in 1978/79 and 1981. However when visited last week the hottest temperature on the floor of the rift was only 13.7 ˚C in a pool of brown water.

The May 2016 eruption was from 3 sources, the most active been the two smaller 'vents/collapse pits' to the west of the main Mud Rift. These were formed in 1981. We have not been able to see anything on our nearest seismographs. It appears to be mainly steam and fine sands-muds involved. There is lots of evidence of fluids flooding in to rift, especially at the west end. Vegetation nearby is stressed and browning off, but is not damaged by the eruption (no broken limbs etc). There is also some evidence of collapse around the edges of the two smaller vents. Over all it appears as a very short lived event, steam driven with a lot of water also involved (think muddy geyser).

There are two large crater lakes nearby; Inferno Crater Lake and Frying Pan Lake. These are jointly monitoring by GeoNet and the BOP and Waikato Regional Council’s. Inferno Crater is remarkable in that the water level fluctuates through 6-9 meters and over flows about every 40 days. Meanwhile Frying Pan Lake is always flowing, today around 80 litres per sec. In the 1980’s it was closer to 100 litres per sec. These crater lakes display a unique interaction, as the water level of Inferno falls the flow from Frying Pan increases and vice versa. This is termed ‘exchange of function’ and is often observed in hot springs.

From January through to early April 2016 Inferno Crater Lake experienced a ‘high stand’, many of these have occurred since the 1970’s when detailed monitoring started of the lakes. During these times more steam energy is present in the Inferno portion of the geothermal system. This was particularily noticed in 1978/79 and 1981. It would appear this increase of steam through the system was responsible for driving the reactivation of the Mud Rift in May 2016. We have located 47 earthquakes within about 10 km of Waimangu in the last year. In the last 6 years we have located 388, which is typically 64 per year.

Volcanic Alert Bulletin RUA 2016/06:
2:00pm Tuesday 7 June 2016; Ruapehu Vol
cano 

Alert Status:
Volcanic Alert Level
 remains Level 2
Aviation Colour Code
remains Yellow

Mt Ruapehu remains in a state of heightened volcanic unrest. The temperature of the summit Crater Lake has declined from 46 ºC and is now 32 ºC. Moderate levels of volcanic tremor continue. Further gas measurements and water samples were collected last week from the lake. The Volcanic Alert Level remains at Level 2 (moderate to heightened unrest). The Aviation Colour Code is also unchanged, at Yellow.

Recent visits to the volcano have confirmed the output of volcanic gas (carbon dioxide CO2, hydrogen sulphide H2S and sulphur dioxide SO2) remains elevated above background levels but is declining. The lake temperature reached a high of 46 ºC on May 11 then the lake started to cool, declining to 30 ºC by June 2. Since then it has risen to the current temperature of 32 ºC. Water samples have been collected from the Crater Lake for chemical analysis. Moderate to low levels of volcanic tremor continue.

Data available at present indicates volcanic unrest continues at Mt Ruapehu. The volcanic alert level for Mt Ruapehu is Volcanic Alert Level 2 (moderate to heightened unrest). The Aviation Colour Code is Yellow. GNS Science volcanologists continue to closely monitor Ruapehu through the GeoNet project.

 


Art Jolly
Duty Volcanologist

Media Contact:
Brad Scott
Volcanologist 

phone 07 3748211

Volcanic Alert Bulletin WI 2016/07:
8:50am Wednesday 25 May 2016; White Island Vol
cano 

Alert Status:
Volcanic Alert Level
 remains Level 1
Aviation Colour Code
remains Green

The level of volcanic unrest at White Island declined following the eruption. Volcano seismic activity has decreased, while the gas output has been variable and is now at typical background levels. No further eruptions have occurred and the Volcanic Alert Level remains at Level 1. GNS staff visited White Island (Whakaari) last week to continue their evaluation of the eruption impacts, sample gases, collect thermal IR images and undertake maintenance of monitoring equipment affected by the eruption on April 27.

Thermal IR images have established very high temperatures are present on a mound in the back of the 1978/90 Crater. This is the same area where a dome grew in 2012. There are two areas of hot gas output and the temperatures ranged from 292 to 337 ºC. These are the highest temperatures we have measured since early 2014 when we measured 450 ºC in the same area. The April 27 eruption removed about 13-15 m of lake floor sediments and now a new lake is starting to form at this lower level on the floor of the crater; the temperature is 49 ºC. The temperature of Fumarole 0 (the largest accessible one) has increased from 178 to 188 ºC.

Observations during this visit of the eruption deposits confirm the explosive nature of the April 27 eruption and the complexity. The eruption did produce very energetic blasts and surges. In places it sheared off or broke survey pegs and markers at ground level. Typical of energetic blast and surge events, the deposit is not very thick, ranging from a few mm to 50 mm in thickness. Ballistic blocks were observed in several locations, suggesting more than one source for them. There is also a ‘wet’ surge deposit that is mainly made up of lake floor sediments (muds, sands and sulphur). It is starting to appear the eruption sequence was: the area around the former Donald Duck Crater collapsed and exploded, then the former lake and the sediments in its basin have been erupted forming the blast and surge deposits. This has lowered the lake floor at least 13 m. This was a very energetic phase with both surge and ballistic phases (some post surge). Following this there has been collapse of the 1978/90 Crater walls. Survivability during the eruption would most likely have been low in areas of the Main Crater floor.

 

The level of volcanic unrest at White Island (Whakaari) declined quickly following the eruption on April 27. The Volcanic Alert level for White Island remains at Level 1. Aviation Colour Code remains Green. GNS Science volcanologists continue to closely monitor White Island through the GeoNet project.

Steve Sherburn
Duty Volcanologist

Media Contact:
Brad Scott
Volcanologist 

phone 07 3748211





 

Volcanic Alert Bulletin RUA 2016/05:
3:00pm Tuesday 17 May 2016; Ruapehu Vol
cano 

Alert Status:
Volcanic Alert Level
 remains Level 2
Aviation Colour Code
remains Yellow

 

Mt Ruapehu remains in a state of volcanic unrest. The temperature of the summit Crater Lake has declined slightly and is now 39 ºC, down from a high of 46 ºC. Moderate levels of volcanic tremor continue. Analysis of water samples collected last week show no change in lake chemistry. The Volcanic Alert Level remains at Level 2 (moderate to heightened unrest). The Aviation Colour Code is also unchanged, being Yellow.

Recent visits to the volcano have measured an increase in the output of volcanic gas. When the weather conditions allow we will be repeating these to see if this continues. The analysis of water samples from the Crater Lake show little change from the previous samples. This implies the Crater Lake geothermal system has not responded to the recent increase in gas and heat through the lake. Moderate levels of volcanic tremor continue and the lake temperature measured by the outlet data logger is now 39 ºC. Some of the decline is caused by rainfall/snow into the lake.

Data available at present indicates volcanic unrest continues at Mt Ruapehu. When weather conditions allow we will be collecting further data. The volcanic alert level for Mt Ruapehu is Volcanic Alert Level 2 (moderate to heightened unrest). The Aviation Colour Code is Yellow.

GNS Science volcanologists continue to closely monitor Ruapehu through the GeoNet project.

Art Jolly
Duty Volcanologist

Media Contact:
Brad Scott
Volcanologist 

phone 07 3748211

 

This week the Volcanic Alert Level (VAL) for Ruapehu was raised to Level 2.

Why did we change the VAL? We based the change on the observation of changes in three parameters we monitor: lake temperature, seismicity (earthquakes) and gas output.

The NZ Volcanic Alert Level system ranges from Level 0 to Level 5. Volcanic Alert Level 2 is defined as ‘moderate to heightened volcanic unrest’ this basically means that the signs of life at the volcano are stronger, and that there is a higher likelihood of an eruption. BUT, and this is the tricky bit: volcanic unrest does not always lead to an eruption. While Volcanic Alert Level 1 is ‘minor volcanic unrest’ - meaning there are signs of life at the volcano, the likelihood of an eruption is small. However, our volcanoes can skip right past Volcanic Alert Level 2 and go straight to Volcanic Alert Level 3. This happened on the 27 April, when White Island went from 1 (minor unrest) to 3 (minor eruption).  

About our monitoring

Our volcano monitoring team base their decision on the VAL on how they think the molten material (magma) or its associated gas and fluids are interacting under the volcano. These interactions can produce changes or symptoms that we can measure (e.g. heat flow, seismicity, ground deformation, gas or chemistry changes). The signs of unrest may be more intense than in Volcanic Alert Level 1, or the interpretation of monitoring data by the team more strongly indicates the movement of magma or its associated fluids. There may be a higher likelihood of an eruption than at Volcanic Alert Level 1.  A volcano can be at Volcanic Alert Level 2 for months, years or even decades.

Why we changed the VAL for Ruapehu

Given the higher lake temperatures, higher gas output and increased seismic activity, we made a call that the mountain had increased its activity to VAL 2. While at the top end of the level we could have steam and gas driven events (geysering) within the Crater Lake, we are not there at the moment.  In the coming days or weeks, we could see activity increase or decrease. If it did increase it would be exciting to see the signs of activity, including steam and gas driven events (geysering) within the Crater Lake! These have often before at Ruapehu (1966-68; June 1978; January-April 1980: February 1982 and May-June 1985). These geysers make for some spectacular viewing but we don’t recommend being too close to the lake should these occur.

Is Ruapehu safe?

It is an active volcano and we should always respect our beautiful mountain. However, although the Volcanic Alert Level has been raised this doesn’t mean you have to avoid the Tongariro National Park. Yes there is a higher likelihood of an eruption developing, however volcanic unrest does not always led to an eruption. Eruptions only affect the summit area of Ruapehu and a few selected valleys. The summit hazard zone defined by DOC should be respected. The public are safe visiting all the normally accessible areas like the visitor centres, cafes, ski fields, lodges, huts, Tongariro Alpine crossing and other lower altitude walks.

NZ Volcanic Alert Level system

In July 2014 the Volcanic Alert Level system used in New Zealand was updated, following a review. One of the big changes was the introduction of two levels to define volcanic unrest (levels 1 and 2). Being able to distinguish between these two levels of unrest was an important part of the need for a change in the Volcanic Alert Level system and is entirely due to advances in volcano monitoring made by the GeoNet project (thanks EQC).

VOLCANIC ALERT BULLETIN: RUA – 2016/04
11:45 am Wednesday 11 May 2016; Ruapehu Volcano

Alert Status:
Volcanic Alert Level
 is raised to Level 2 (change from 1)
Aviation Colour Code raised to Yellow (change from Green)

Recent visits to the volcano have confirmed an increase in the output of volcanic gas from Mt Ruapehu’s Crater Lake. Moderate levels of volcanic tremor continue and the lake temperature measured by the outlet data logger is 45 ºC. The increase in gas output, the high lake temperature and continued seismicity suggest that Ruapehu is at a higher level of volcanic unrest. As a result, GNS scientists revise the Volcanic Alert Level to Level 2 (moderate to heightened unrest). The Aviation Colour Code is also changed, from Green to Yellow.

We made two monitoring visits to Mt Ruapehu yesterday, one was a gas flight to measure the gas output and the other was to sample the Crater Lake water and make additional ground based gas measurements. Volcanic gas measurements indicate an increase in the amount of both carbon dioxide (CO2) and sulphur dioxide (SO2) output. The ground based gas measurements were complimentary to the airborne data.

Seismic activity at Mt Ruapehu is usually dominated by volcanic tremor. Since the volcanic earthquakes in late April the seismicity has been dominated by volcanic tremor at varying levels. The level of tremor has increased but is not exceptional in terms of the last few years.

The temperature of the Crater Lake as measured by a data logger near the outlet has been rising and since mid-April 2016 and has risen from 25 °C to 46 °C.  For the last couple of days it has ranged between 45 and 46 ºC.

Taken together these data now indicate more volcanic unrest at Mt Ruapehu. The increased gas output coupled with high heat flow and volcanic tremor imply a higher likelihood of activity. At this time these changes at Ruapehu are considered sufficient to change the Volcanic Alert Level. The volcanic alert level for Mt Ruapehu is now raised to Volcanic Alert Level 2 (moderate to heightened unrest). The Aviation Colour Code has also changed, from Green to Yellow.

GNS Science volcanologists continue to closely monitor Ruapehu through the GeoNet project.

 

Geoff Kilgour
Duty Volcanologist

 

Media Contact:
Brad Scott
Volcanologist


07 3748211


GeoNet is a collaboration between the Earthquake Commission and GNS Science.

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