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Overnight on Tuesday a moderately large avalanche flowed into the Crater Lake at Mt Ruapehu, with approximately 30 000 tons of ice and snow slipping in to the lake. The GeoNet seismographs near the summit of Mt Ruapehu recorded the ground vibration caused by the avalanche, appearing as a ‘unusual’ earthquake that in someways looked like a volcanic earthquake. Our Crater Lake temperature sensor recorded a rapid drop in the temperature of the lake, from 15 to 8 °C. Over the next few hours the lake reheated to 15 °C and appeared unaffected by the avalanche.

In the past, drops in the lake temperature have also occurred following small eruptions when large volumes of ice and snow are washed into the lake, entrained by water ejected outside the lake and draining back in. Although the lack of signal on our air pressure sensors strongly suggested that no eruption had occurred, on Tuesday night, it was important to confirm the cause, said GeoNet Duty Volcanologist Dr Tony Hurst. GeoNet and the Department of Conservation conducted an observation  flight over the Crater Lake on Wednesday to ascertain the impacts and confirm the cause of the rapid drop in the lake temperature.  Substantial avalanche scars and deposits were observed during the flight, confirming that the observed seismic signal and change in the lake temperature overnight were related to the avalanche depositing thousands of tons of ice and snow into the Crater Lake.

Although the lake has been relatively cold over the past weeks (15 °C.), heat is always being added to the lake from the vents on the lake floor.  Because of this sustained heating, the lake quickly recovered from the sudden inflow of cold snow and bounced back up to its pre-avalanche temperature.  If the heat flow wasn’t present the lake would have cooled down and stayed cooler. The GeoNet volcano gas team had also conducted a gas flight last Friday and measured typical amounts of volcanic gas from the Crater Lake, confirming no unusual level of activity at the volcano. The Volcanic Alert Level remains at Level 1.

 

In December 2013 GeoNet added a new web camera at White Island. Placed on the western rim of the Main Crater the camera can give really great views of the Crater Lake, when steam and gas allows. An important part of volcano monitoring is visual observations, and a great way to achieve this is by the use of remote cameras. The GeoNet monitoring team soon realised they could see the level of the Crater Lake changing but couldn’t quantify the changes.

In September 2014 a ‘target’ was established on the top of Donald Mound that was large enough to see in the web camera images. This then gave the GeoNet team a reference point on the images from the web cameras. From this they are able to track the water level in the Crater Lake by counting the number of pixels in the image below the target. Since the west rim camera was installed in 2013 they have been able to track a 5 metre rise in the water level of the lake. From December 2013 to May 2014 the lake rose about 3 metres and then remained unchanged until June 2015. Since then the water level has risen another 2 metres.

The Crater Lake at White Island has had quite a history of change since it first 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 to again evaporate the lake away. Small eruptions followed in August and October 2013 before the lake started to reform in November 2013.

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Volcanic Alert Bulletin TON 2015/01 - Tongariro Volcano: Volcanic Alert Level 0;  Aviation Colour Code Green;  11.50 am  Wednesday 19 August 2015

Volcanic unrest at Tongariro (Te Maari) has declined steadily since the eruptions in 2012. All monitoring indicators suggest that the unrest episode that triggered the 2012 eruptions is now over. While high temperature fumaroles are still present at the Te Maari crater, chemical analyses suggest that the gases are mostly from the hydrothermal system (steam); the heat is sustained from cooling magma remnants at depth. GNS Science lowered the Volcanic Alert Level to 0 (no volcanic unrest) from Level 1 (minor unrest).

Since Tongariro last erupted in November 2012, the activity at the volcano has been steadily declining. For example, shallow volcanic earthquakes are now extremely rare or absent and are of a similar number to pre-2012 levels. GNS Science staff has made numerous visits to the volcano to measure the temperature and sample the gases within the fumaroles. Analysis of these gas samples show a steady decline in the magmatic contribution within them, which means that the fumaroles are now dominated by hydrothermal fluids (heated ground water i.e., steam). There is a large hydrothermal system under Mt Tongariro that supports the surface features at places like Ketetahi, Te Maari, Red and Central craters. In addition, the automated sulphur dioxide (SO2) gas detectors (FlySpec) jointly operated by DOC and GeoNet since April, have barely recorded any SO2, a major indicator of volcanic gas rising from depth. The gas levels are basically at or below detection levels. Taken together, these results indicate that the minor unrest present since the 2012 eruptions has declined significantly. The steam plume that emanates from the Te Maari vent (like the one from Ketetahi) is likely to remain active for the foreseeable future.

"The Volcanic Alert Level was raised to Level 1 from Level 0 on July 20, 2012 largely due to the increased earthquake activity beneath the volcano. This was the first signs of volcanic unrest at that time”, said Dr Nico Fournier Head of Volcanology GNS Science. “On August 6, 2012 Tongariro erupted from the Te Maari vent(s) in a series of short explosions, impacting the local area. Later that year on November 21, the volcano erupted again through the same vent area” said Dr Fournier. Since the November 2012 eruption, Tongariro has been at Volcanic Alert Level 1. “We now consider the volcanic unrest associated with the 2012 eruptions to be over, hence the Volcanic Alert level is being lowered to Level 0”, said Dr Fournier from GNS Science.

GNS Science has now lowered the Volcanic Alert Level to 0 from Level 1. GNS Science continues to closely monitor Tongariro 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.

The Aviation Colour Code for Tongariro remains at Green. Aviation Colour Codes are based on four colours and are intended for reference only in the international civil aviation community.

 

Geoff Kilgour
Duty Volcanologist

 

Media Contact:

Brad Scott
Volcanologist  07 3748211

The temperature of the summit Crater Lake at Mt Ruapehu typically ranges between about 15 and 40 °C. This has been a common feature of the lake since it reformed in 1999-2000. The lake was removed during the 1995 and 1996 eruptions and took several years to refill and become established. GeoNet obtains daily temperatures from the lake using a data logger system that sends data via a satellite link.

The lake reached a high of 37-38°C at the start of April 2015 and then started to cool. During the period 7- 11 August the temperature was just under 15 °C, since then it has been stable at 15 °C. It would appear the cooling cycle is ending and the lake may start to reheat soon. In our last update from the Crater Lake we mentioned the sampling we had achieved, when the weather finally improved. The GeoNet chemists have finished the analysis and report the results are typical of the Crater Lake waters when there is a small indication of the vents been sealed. That is when less gas and heat reaches the lake. This is usual during cooling trends in the Crater Lake.

During the last 50 or so years Mt Ruapehu has erupted often and one trend we have noticed is that the eruptions occur from either a hot or cold lake. They do not occur every time the lake gets hot or cold, however if one does occur it will usually be at one of these extremes. This becomes a time when we pay some extra attention to the status of the volcano.  A good time just to check out the response plan and make sure all is good to go if needed.

Further sampling and visit to the Crater Lake is planned later this week or next, weather allowing, as part of the standard GeoNet monitoring programme for Ruapehu.

Upper Te Maari crater at Mount Tongariro was the site of small eruptions on 6 August and 21 November 2012, the first eruptive activity there since 1928 and the larger eruptions in 1896-97. The eruptions produced small ash clouds up to 8 km height and were accompanied by volcanic landslides, blasts and rocks being tossed more than 2 km from the vent.  Today emission of steam and gas, seen as a continuous white plume above the crater are a feature of the mountain. Motorists driving around the area often report the gas odour. Most of the gas is coming from a large vent and crack in a cliff just above the Upper Te Maari crater.


The steam and gas vents, known as ‘fumaroles’, are slowly cooling, however the temperature of the hottest vent remains over 380 °C. GeoNet’s gas chemists report there is still volcanic gas present, but this is slowly decreasing, like the temperature. The major gas is steam, but we still measure small amounts of carbon and sulphur dioxide (CO2 and SO2) and other volcanic gases.

These eruptions and volcanic unrest at Ngauruhoe in 2014, saw GeoNet boost the monitoring systems in the area, some on a temporary basis. Additional data is now obtained from 5 seismographs to record the volcanic earthquakes, 5 GPS’s to measure ground movements, 3 air pressure wave sensors to record air waves from future explosions and 3 web cameras. These are complimented by 2 Flyspec gas sensors installed by DOC and GNS Science. What was already a effective monitoring system in 2012 is now one of the best volcano monitoring networks in New Zealand.    

Monitoring of Tongariro by GeoNet saw the unrest developing, but the GeoNet team was just as surprised as everyone else when the eruption occurred just on midnight August 6. The eruption affected the Tongariro Alpine Crossing, which has tracks running within 1.5 km of the Te Maari vents and resulted in its closure in August 2012. The eruptions provided many research opportunities for the volcanologists and social scientists interested in volcanology. Well established response and recovery planning was also tested at all levels. The co-ordinated science and risk management response saw robust decisions being made about visitor and scientist safety, leading to new electronic warning signs on the track being established by DOC, letting visitors know more about the volcanic risk and track status in near real time.

As the activity declined at Tongariro, GNS Science has lowered the Volcanic Alert Level from Level 2 to Level 1 in November 2012 and the Aviation Colour Code to Green from Yellow in March 2013. The Volcanic Alert Level remains at level 1 (minor volcanic unrest).

GeoNet’s volcano teams plan to sample the summit Crater Lake at Mt Ruapehu about once a month. At this time of the year the weather can be challenging.  Late last week the weather presented the opportunity and the lake was visited by helicopter.  

The lake is currently cooling from a high of 39.6 °C on 25 April, now being only 17.4 °C. This is very normal for the Crater Lake.  Over a period of 9-14 months the lake will typically heat to around 40 °C and then cool to around 16 °C.  The lake is overflowing via the outlet in to the upper Whangaehu Valley.  Conditions didn’t allow for the flow to be measured - it usually ranges around 20-50 litres per second.  The scientists observed signs of convection in the lake and noted the colour remains grey, but is now a lighter grey colour. This is normal as the lake cools and some of the disturbed sediment in the lake settles.  The water and gas samples will be analysed by the GNS Science laboratories.

The GeoNet seismic network at Ruapehu continues to record volcanic tremor, however the level of volcanic tremor has declined since late June. Volcanic tremor is always present at Ruapehu, but the level does vary a lot. Research suggests volcanic tremor is linked to both hydrothermal and magmatic processes at Ruapehu. 

Keen volcano watchers may have noticed we added a new web camera at Tongariro last week. The new camera has been installed on Pihanga as part of a revision and upgrade of our data-links in the area. The new Pihanga camera is about 10 km south-east of the one on Kakaramea and looks more along the eastern side of Tongariro towards Ngauruhoe, with Lake Rotoaira in the foreground. The views from the two cameras complement each other.

In the images from the weekend we see steam columns from Te Maari. This camera, like all of our volcano cameras, is in fact ‘two’ cameras, a standard daylight camera and a specialised ‘low light night’ camera - we will have images at night as well when conditions allow.

Volcano monitoring is made up of many parts - an important part is visual observations, and a great way to achieve this is by the use of remote cameras. Advances in camera technology and, more importantly in this case, the upgrade of the data-links, are allowing us to bring back more data. As with all of our remote camera installs the local conditions are going to dictate how many useful images we get from the site. 

GeoNet chemists visited White Island last Thursday and Friday to sample and collect gas from the high temperature fumaroles. Fumaroles are high temperature vents which emit steam and gases such as carbon dioxide, sulfur dioxide, hydrogen chloride, and hydrogen sulfide.

Fumarole 0 (zero) is the hottest accessible fumarole on the island. The temperature during sampling was 168 °C, been 8 °C warmer than the previous sampling.  They also sampled Noisy Nellie at 100.2 °C and 13a at 100 °C.  The temperature of these two fumaroles have not changed appreciably during the last year. We usually sample the fumaroles every 3 months.

Intermittent volcanic tremor declines as Ruapehu Crater Lake starts to cool

Ruapehu Volcano

Volcanic Alert Level 1

Aviation Colour Code: Green

2.30 pm Monday 11 May 2015

 

The level of seismic activity has decreased. “During April we recorded intermittently moderate to strong levels of volcanic tremor at Mt Ruapehu, however since April 28

the level has more than halved” reported volcanologist Brad Scott.

Mt Ruapehu’s Crater Lake has started to cool. The temperature had declined to about 37°C in late April and is now at 34°C. The lake has been in a heating phase which started in late 2014 when the lake was 15°C, reaching a peak of over 40°C in late January–early February 2015 (see RUA 2015/02).

The Crater Lake was sampled on April 24 and no changes are apparent in the chemistry of the lake water. No other changes have been observed at the Crater Lake.

Mt Ruapehu remains at Volcanic Alert Level 1 (minor unrest). 

The Volcanic Alert Level ranges from 0 to 5 and defines the current status at a volcano.

The Aviation Colour Code for Ruapehu is Green. Aviation Colour Codes are based on four colours and are intended for reference only in the international civil aviation community.

GNS Science continues to closely monitor Ruapehu through the GeoNet project. http://www.geonet.org.nz/volcano

 

Steve Sherburn

Duty Volcanologist

 

Media Contact:

Brad Scott

Volcanologist  07 3748211

Ruapehu Crater Lake heating and intermittent volcanic tremor.

Ruapehu Volcano

Volcanic Alert Level 1

Aviation Colour Code: Green

3 pm Wednesday 29 April 2015

 

The Crater Lake is currently in a heating phase which started in late 2014  when the lake was 15°C, reaching a peak of over 40°C in late January–early February 2015 (see RUA 2015/01). The temperature declined to about 31°C in mid March and is now at 37-39°C. We have not observed any other changes at the Crater Lake.

Over the last 2-3 weeks we have been recording intermittent moderate to strong levels of volcanic tremor at Mt Ruapehu, which has been some of the strongest we have seen in the last 8 years. The signals are similar to those in 2006 and 2007 but weaker than those recorded in 1994/1995.

Historically we have not seen a direct relationship between volcanic tremor and discrete volcanic eruptions or sequences of eruptions. However it is one of those signals often present before, during or after enhanced volcanic unrest. Mt Ruapehu remains at Volcanic Alert Level 1 (minor unrest).  

 

The Volcanic Alert Level ranges from 0 to 5 and defines the current status at a volcano.

The Aviation Colour Code for Ruapehu is Green. Aviation Colour Codes are based on four colours and are intended for reference only in the international civil aviation community.

GNS Science continues to closely monitor Ruapehu through the GeoNet project. http://www.geonet.org.nz/volcano

 

Art Jolly

Duty Volcanologist

 

Media Contact:

Brad Scott

Volcanologist  07 3748211

Recent volcanic unrest at Ngauruhoe ends: Volcanic Alert Level lowered to Level 0

Volcanic unrest at Ngauruhoe has declined to representative background levels over the past three weeks. The number of volcanic earthquakes recorded near the volcano is now at typical background numbers. No other indicator of unrest has been detected. GeoNet lowered the Volcanic Alert Level to 0 (no volcanic unrest) from Level 1 (minor unrest).

It is now three weeks since GeoNet last recorded a slightly unusual number of shallow volcanic earthquakes at Ngauruhoe, indicating volcanic unrest. Furthermore, no anomalous ground temperature or unusual level of gas emission were detected at the summit, during visits, indicating that the minor unrest recently occurring at Ngauruhoe has now ceased. GeoNet accordingly lowered the Volcanic Alert Level to 0 from Level 1. GNS Science continues to closely monitor Ngauruhoe and our other active volcanoes through the GeoNet project

The Volcanic Alert Level was raised to Level 1 from Level 0 on March 20 in response to the changes in volcanic earthquake activity. In March, the number of events per day has ranged from 1 to 67, which was similar to previous minor episodes of unrest between 2006 and 2010.

The Volcanic Alert Level ranges from 0 to 5 and defines the current status at a volcano.

The Aviation Colour Code for Ngauruhoe remains at Green. Aviation Colour Codes are based on four colours and are intended for reference only in the international civil aviation community.

 

Nico Fournier

GeoNet volcano duty officer

 

Information Contact:

Brad Scott

Volcanologist  07 3748211

 

Background information:

Volcano activity in New Zealand: http://www.geonet.org.nz/volcano

Volcanic Alert Levels; http://info.geonet.org.nz/display/volc/Volcanic+Alert+Levels

Past Volcano Alert bulletins: http://info.geonet.org.nz/blog/volc

 

 

 

 

Seismic activity around Ngauruhoe has remained slightly elevated this last week. Visits were made to install additional seismic equipment and measure fumarole temperatures.  

Ngauruhoe unrest continues: Volcanic Alert Level 1

The Volcanic Alert Level was raised to Level 1 from Level 0 on March 20 in response to the changes in earthquake activity, indicating minor volcanic unrest. The GeoNet seismographs around Mt Ngauruhoe have continued to record earthquake activity. Our analyses indicate these earthquakes are shallow, occurring at depths of less than about 5 km. Since March 1 the number of events per day has ranged from 1 to 67, which is similar to previous episodes between 2006 and 2010.

We have visited the summit crater and eastern outer rim to measure fumarole temperatures and obtain thermal IR images (see below). GNS Science gas chemist Agnes Mazot commented, “the temperatures in the summit crater and on the outer eastern rim are unchanged from our previous visit in January 2015. The maximum temperature measured was 87 °C, on the outer eastern rim. The temperatures in this area have ranged 81 to 87 °C over the last 17 years”.

Thermal IR (InfraRed) images are one method of mapping heat flow over large areas, some of which may not be accessible. The image below shows part of the inner north wall of the summit crater. Collecting repeat images will allow us to ascertain if there are any changes. The warmest area is the white area near the centre of the image, being 35 °C.

 

 

 

Thermal IR image and visual image of the inner north wall of the summit crater, 27 March 2015.

The current change at Ngauruhoe indicates the volcano has entered a state of volcanic unrest, like we have recorded several times in the last 30 years. No previous periods of unrest have resulted in a volcanic eruption. The outcome of this unrest is more likely than not that there will be no eruption in the short term, like during the 2006-2010 unrest.

The last significant eruption at Ngauruhoe was in 1975.  Earthquakes are not unusual near Ngauruhoe but it is some time since we last recorded significant numbers or events above magnitude 1. Similar numbers, but smaller events occurred in December 2014. Other swarms of earthquakes near Ngauruhoe occurred in 1983, 1991, 1994, 1995 and again 2006-2010, but otherwise Ngauruhoe usually has little earthquake activity.

We continue to monitor Ngauruhoe closely and will release updated information as it is available or necessary.

The Volcanic Alert Level ranges from 0 to 5 and defines the current status at a volcano.

The Aviation Colour Code for Ngauruhoe is Green. Aviation Colour Codes are based on four colours and are intended for reference only in the international civil aviation community.

GNS Science continues to closely monitor our active volcanoes through the GeoNet project. http://www.geonet.org.nz/volcano

Information Contact:

Brad Scott

Volcanologist  07 3748211

 

 

 

  

23 March 2015, 4:00pm - Volcanic Alert Level rises to Level 1; Aviation Colour Code remains Green (no change)

Seismic activity around Ngauruhoe has increased above the typical background level, indicating minor volcanic unrest. Consequently GNS Science has raised the Volcanic Alert Level to level 1 (minor volcanic unrest) from 0 (no volcanic unrest).

During the last two to three weeks there has been an increase in the number and magnitude of earthquakes being recorded by the GeoNet seismographs around Mount Ngauruhoe. Initial analysis indicates these earthquakes are shallow, occurring at depths of less than about 5 km.

The last significant eruption at Ngauruhoe was in 1975. Earthquakes are not unusual near Ngauruhoe, but it is some time since we last recorded significant numbers or events above magnitude 1. Similar numbers, but smaller events occurred in December 2014. Other swarms of earthquakes near Ngauruhoe occurred in 1983, 1991, 1994, 1995 and again between 2006 and 2010, but otherwise Ngauruhoe usually has little earthquake activity.

The Volcanic Alert Level was raised to Level 1 in June 2006 and then lowered to Level 0 in December 2008 in response to the earthquake activity at that time. No other parameters we measure at Ngauruhoe (gas, temperature) changed during these times.

The current change at Ngauruhoe indicates the volcano has entered a state of volcanic unrest, like we have recorded several times in the last 30 years. No previous periods of unrest have resulted in a volcanic eruption. The outcome of this unrest is more likely than not that there will be no eruption in the short term, like during the 2006-2010 unrest.

We continue to monitor Ngauruhoe closely and will release updated information as it is available or necessary.

The Volcanic Alert Level ranges from 0 to 5 and defines the current status at a volcano.

The Aviation Colour Code for Ngauruhoe is Green. Aviation Colour Codes are based on four colours and are intended for reference only in the international civil aviation community.

 

Art Jolly
Duty Volcanologist

Media Contact
Brad Scott
Volcanologist 07 3748211

 

Starting last Wednesday (March 4th) the GeoNet seismometer network between Taupo and the Tongariro National Park started recording a swarm of small earthquakes. They locate about 10 kilometres west north west of Tokaanu. We have been able to locate 73 of the events so far. Their magnitudes ranged from M0.8 to M 2.8, while the depths ranged between 5 and 14 kilometres, with most being 7-8 kilometres deep.

Volcanologist Brad Scott commented that this is very typical of earthquake swarm activity, when many earthquakes are recorded over a period of time.  Swarms are often characterised by no one main or large event, with many of the events being about the same size. Only four of the events in this swarm are larger than M 2, another eleven are larger than M1.5. There are also many events to small to be located.

Some local residents have felt these events. The events were too small to be widely felt or cause any significant damage.  In 2008 there was a similar swarm about 3-5 kilometres east of where this swarm is occurring.

Crater Lake heating phase reaches peak.

Ruapehu Volcano

Volcanic Alert Level 1

Aviation Colour Code: Green 

10.00am Friday 30 January 2015

Mt Ruapehu’s Crater Lake has been heating again. Since early December 2014 the temperature has risen from 15 °C and has now reached temperatures over 40 °C. Similar temperatures were reached in March 2011 and April 2014, before the lake cooled.

Data from a recent Crater Lake sampling (14 January) has shown there are several changes in the lake chemistry. In particular we see evidence for increased amounts of volcanic gas discharging through the lake. The increase in the lake temperature and gas discharge is probably indicative of renewed heating of the hydrothermal system under the lake. Observations from recent visits and pilot reports confirm some convection is present in the lake. The lake has changed from a blue/green colour to light grey as a consequence.

Volcanologist Brad Scott said “Since 1950, the temperature of Crater Lake ranged from 9°C to 60°C. About 25% of the time the lake is warmer than 37°C with an average of about 30°C. Cycling of the lake temperature is not unusual and we have seen 5 heating cycles since 2010”.

Mt Ruapehu is an active volcano with a well-established monitoring regime in place and documented historic eruption record. In the past changes like those we are observing now have had two typical outcomes:

  • In most cases the lake temperature reaches a maximum (40-42 °C), which is sustained for a short time (days-weeks) and then the lake starts cooling with no eruptive activity. At present the lake appears to have stopped heating.
  • More rarely the lake temperature continues to increase and minor steam eruptions may start in the Crater Lake. This is very similar to the climax of many heating episodes between 1985 and 1995. If the lake temperature continued to increase larger volcanic eruptions could occur.

The Volcanic Alert Level for Ruapehu remains at Level 1, indicating minor volcanic unrest. The Volcanic Alert Level ranges from 0 to 5 and defines the current status at a volcano.

The Aviation Colour Code for Ruapehu is Green. Aviation Colour Codes are based on four colours and are intended for reference only in the international civil aviation community.

GNS Science continues to closely monitor Ruapehu through the GeoNet project. http://www.geonet.org.nz/volcano

Natalia Deligne

Duty Volcanologist

 

Media Contact:

Brad Scott

Volcanologist 


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

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