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Monday  

Our volcanologist-at-large, Brad Scott, updates us on what’s been going on with our volcanoes over the last couple of weeks. Post the Kaikoura earthquake we have maintained a close watch on the volcanoes. To date we have not seen any changes that can be directly related to the earthquake or the aftershock activity. We have seen changes, as we always do at the active volcanoes, but do not consider any are directly related to the Kaikoura event. However, we can’t eliminate the possibility that activity may change in relation to more shakes around the country.  

Volcano rundown: let’s start at the top

 

Starting offshore North of New Zealand, we work our way south along the Kermadecs, beginning with Monowai submarine volcano. There has been no activity noted since 11-12th November. However, we did notice a random pumice raft in the middle of the ocean near Tonga but this looks unrelated to Monowai.

Next is Raoul Island, nothing new is apparent there, only the Crater Lakes showing their usual summer warming cycle, due to the warmer weather.

A team visited White Island (Whakaari) and our ever watching Dino, last Thursday with a film crew and made several observations. The temperature of the main vent in the active crater has declined, down from 280 to around 140 °C. The small pools of water on the crater floor are getting smaller. The temperature of the hottest accessible fumarole (steam vent) remains around 180 °C. The gas flux has varied from around 300 to 600 tons per day of SO2. Overall the situation remains very similar at White Island (Whakaari) to how it was a couple of weeks ago.

Auckland Volcanic Field is also quiet too, no earthquakes near there. Moving south, Okataina Volcanic Centre (this includes Tarawera) is quiet, just a couple of small shallow earthquakes nearby.

The big news in volcano land this week is the that there has been a small steam (hydrothermal eruption) in Lake Rotorua. Eruptions have been known in this area all through our written history (1830 – present), so it’s not too unusual. The occurrence of steam eruptions has been variable in Rotorua, with many during the exploitation of the geothermal system, however they declined after the bore closure (1987). The last significant one was in 2001. We’ll be keeping a close eye on this latest hydrothermal eruption but, as this is pretty much business as usual for this system, we aren’t too concerned about it. We went down to check out the eruption and it didn't leave much interesting evidence

Our central volcanic zone is pretty quiet too. Taupo Volcanic Centre is quiet, just a couple of small earthquakes. Further south, the Tongariro-Ngauruhoe area is very quiet, again just a couple of small earthquakes. A team visited Te Maari and measure 308 °C from the vent here. The volcanic tremor at Ruapehu remains weak. The lake temperature is now 24.5 ˚C, continuing to slowly decline.

Mt. Taranaki continues its silent watch over the West Coast of the North Island.

So that ends our tour. And thankfully, it looks like the volcanoes have continued to ignore the Kaikoura earthquake sequence.

 

 

 

A RNZAF flight on Wednesday November 16 has reported floating pumice to the west of Minerva Reef in an area about 600 km SE of Fiji and 500 km SW of Tonga. We are not aware of any active submarine volcanoes in this area. The nearest active submarine volcano is Monowai (400 km SE) and we know it was active on November 10-11. Monowai usually does not produce pumice rafts, just discoloured plumes.

We have analysed some satellite images from the area using https://worldview.earthdata.nasa.gov/ and can see the pumice rafts in images from November 15 and 16. They extend for more than 100 km in the images. We have not as yet been able to ‘back track’ the pumice in older images to confirm a source location. The pumice is generally seen around 179°W and 179°E and 23° 20” S.

 

In October 2012 a much larger pumice raft was found (https://goo.gl/8A7c57) and later we found out it came from Harve submarine volcano.

The Kaikoura Earthquake and Tsunami have been keeping us all very busy but don’t worry our volcanologists have still been keeping an eye on the volcanic activity around the country. First off, we’ve had a lot of questions about how the M7.5 Kaikoura Earthquake has affected our volcanoes. From what we can tell, these systems are separate and the large earthquake(s) haven’t affected our volcanoes.

Volcanologist Brad Scott has prepared the following tour for us as we thought it would be good to give you a bit of an update tour of our temperamental friends, New Zealand’s volcanoes.

Volcano rundown: let’s start at the top

Starting offshore North of New Zealand, we work our way south along the Kermadecs, beginning with Monowai submarine volcano, which had a brief bit of activity over the 11-12th November that lasted about 24 hours. This is normal behaviour as we see a few days’ of activity every month. Next is Raoul Island, nothing new is apparent there, only the Crater Lakes showing their usual summer warming cycle (climate induced). And it’s a similar situation at White Island. The volcanic tremor levels remain very low and although there have been a couple of earthquakes nearby we see that every other week as well. Auckland is quite too.

Moving on-shore, Okataina Volcanic Centre (this includes Tarawera) is quiet, just a couple of small shallow earthquakes near Kawerau and a half dozen to the south in Waikite Valley (a place no stranger to small earthquake swarms). There were also a couple of earthquakes near the Wairakei geothermal system. Taupo Volcanic Centre is quiet, just 2 events so far this week.However, it is a very different story north of Kuratau (near Turangi) which experienced a sequence of earthquakes between the 10th and 13th of November. We had the story ready to run on Monday, but decided to hold off publishing it because we were focused on the bigger issues of the Kaikoura earthquake.

The sequence has come in four parts to date:

  • The first, which included the largest earthquakes, started on November 10 and appeared as a typical main-shock after-shock sequence. The largest of the 27 earthquakes in this part was a magnitude 3.3.
  • After a quiescence (aka a geological power nap) of about 21 hours, the second sequence started. It behaved much more like a typical Taupo Volcanic Zone swarm and included 52 earthquakes.
  • The third part of the sequence started about 11 hours after the second and was also swarm like (32 earthquakes).
  • The fourth part included three magnitude 3 earthquakes and an isolated magnitude 3.2 earthquake on the eastern side of the lake (9 events). This part dropped off before midnight Sunday/Monday and so far has not notably reactivated following the M7.5 sequence - i.e. since the first Kaikoura earthquake.

 The earthquakes range in magnitude from a little less than 1.0 to magnitude 3.3. The earthquakes are located between 5 and 11 km deep, with the majority of these between 7-8 km. Small shallow earthquakes like these will be well felt by local residents and we have received many felt reports from the area. It is not clear if the sequence has finished yet. Prolonged earthquake swarms (sequences) are a regular feature of the Taupo Volcanic Zone. One near Matata in the mid-2000’s lasted several years.

Further south, the Tongariro-Ngauruhoe area is very quiet, just a couple of small earthquakes. The volcanic tremor at Ruapehu is slowly declining, heading back towards normal background levels. The lake temperature is now 31 ˚C, slowly declining from the recent maximum of 39 ˚C.

Mt. Taranaki continues its silent watch over the West Coast of the North Island.

So that ends our tour. And thankfully, it looks like the volcanoes have ignored the Kaikoura earthquake(s).

VOLCANIC ALERT BULLETIN: RUA – 2016/10
2.15pm Monday 31 October 2016;
Ruapehu Volcano

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

Since early September, Mt Ruapehu’s Crater Lake had been heating at a rate of around 1°C per day, reaching a maximum of 40ºC on October 4. The lake temperature has cooled slightly since then and is now hovering around 37°C. After October 18, the level of volcanic tremor under Mt Ruapehu increased in strength. Volcanic tremor is always present at Mt Ruapehu, however the level can vary.

An increase in the strength of volcanic tremor began on October 18, where a sharp increase was noted before the energy declined a day later. Subsequent tremor increases occurred again on October 25 and 28, and currently remains higher than normal. These tremor pulses do not appear to be related to any variation in the lake temperature. Our records show that similar periods of increased volcanic tremor were present May-June 2016, again when the lake temperature was high. Importantly, no eruptive activity or geysering was noted in Crater Lake during the previous periods of volcanic tremor.

Weather conditions have not been ideal for mountain observations. Nevertheless, our scientists will be visiting the lake to collect water samples for further analysis and making a gas flight when the weather conditions improve.

The active crater at Mt Ruapehu is occupied by Crater Lake and it displays temperatures that typically range between about 15 and 40°C and the phases can last between about 9 and 20 months. The lake cooled to a minimum of 12°C in mid-August and then remained at 13-14°C until early September when it started to heat again and reached a peak of 39.8°C on October 4.

GNS Science volcanologists continue to closely monitor Ruapehu through the GeoNet project. The Volcanic Alert Level for Mt Ruapehu remains at Level 1 (minor volcanic unrest) and the Aviation Colour Code also remains unchanged at Green. 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.

Brad Scott
Duty Volcanologist

 

 

2016 Volcano Short Course

Following the 1995-1996 eruptions of Mt Ruapehu, which were the largest eruptions in New Zealand for 50 years it was realised there was a need for more detailed education about ‘The Volcano Problem’. In December 1997 GNS held its first volcano short course; Volcanoes and Society in Taupo. Now 19 years later the course is still popular and fulfilling a need with emergency managers and operational staff, engineering lifelines, the Ministry of Civil Defence and Emergency Management, students, communications specialists and staff from a SW Pacific volcano observatory.

In 1997 the course covered off: The Volcano Problem, Volcanic Impacts and Mitigation, Volcano Surveillance, Warnings and Alerts and Planning to Respond. In 2016 the course covered: The Volcano Problem, Near Vent Hazards, Volcanic Ash Impacts, Ash and Gas Impacts on Health, NZ Volcanoes, The IWI perspective, GeoNet Volcano monitoring, Warning Communications, Challenges of Modern Media, Communicating Hazard and Risk, Management of Risk and case studies. The content has grown as have the issues we face from volcanoes.  This year 15 people attended the course and the Field Trip.

Presenters came from a variety of organisations, including the University of Hawaii, GNS Science, Joint Centre for Disaster Research, BOP Emergency Management, the Ministry of Civil Defence and Emergency Management and Auckland University. Two of the presenters also presented on the 1st course back in 1997. The field trip covered an introduction to ‘Caldera Volcanoes’, aspects of geothermal hazards, volcanic land forms, the 1886 Tarawera eruption and faulting associated with the large caldera volcanoes. The course was well received by the participants. The 2017 course will mark the 20th running of the Volcano Short Course.

Recently we had a short lived episode of volcanic ash emission at White Island and our geologists collected some samples. The ash was what geologists call ‘very fine’, that is the particles are very small. They reported back to us that the ash ‘didn’t show any signs of new magma been involved. So how do they know this?

The traditional method is to place the ash sample under a microscope and describe what you see. This time around they did that, as well as putting some in the new Scanning Electron Microscope (SEM) that our geothermal team has obtained. It has very powerful electron optics. One of the features of an SEM is that you can get up to 60,000X magnification. With this extra magnification we can see all sorts of detail in the ash fragments.

Below are two images of volcanic ash. In the right image is some ash from Yasur volcano in Vanuatu. Here explosions happen very 5-10 minutes from craters full of molten lava and the explosions produce a volcanic ash that is made up almost entirely of fresh magmatic particles. You can see the indentations from the gas bubbles and the ‘long’ needle like structures of the volcanic glass.

In the other image is some of the ash we collected from White Island last week. You can see it is made up of lots of angular fragments and crystals. Most of this sample is broken up rock and crystal. This sample is a marked contrast to the one from Yasur. As we can not see any fresh magmatic glass or material with gas bubbles, we are confident there is no new magma at White Island. The new SEM is going to be a big help when it comes to looking at fine ash samples from our eruptions.

Volcanic ash hazards can be very far reaching and are disruptive and damaging. Volcanic ash affects more people, infrastructure and life than any other eruptive phenomena. It consists of very small jagged pieces of rock and volcanic glass. Ash is abrasive, mildly corrosive and conducts electricity when wet. It does not dissolve in water.

VOLCANIC ALERT BULLETIN: WI – 2016/13

15:20 Monday 3 October 2016

Volcanic Alert Level 1 (no change)

Aviation Colour Code: Yellow (no change)

Observations during a visit to White Island on Friday have confirmed that a large part of the gas is now being emitted from one ‘joint’ vent on the lava outcrop at the back of the crater. The joining of the vents has resulted in a stronger and noisier gas flow from this vent. The temperature has declined slightly, it is now only 250 °C, down from 300 °C. The other significant change is the disappearance of the shallow lake. The lake was about 3 m deep and has now drained to leave some small ponds. The water level started to drop on the 24th and by the 26th of September the lake was gone and remains so. The seismic and acoustic activity remains low, and although the gas flux is difficult to measure (due to wind conditions) it doesn’t appear to have changed substantially.

Recently we have also experienced some issues with the power supplies for some of our remote monitoring gear, mostly related to the accumulative effect of the weather (little sun) and ash on the solar panels. One of the cameras had an issue with the data card. On Friday a team visited the island armed with a new camera, batteries, glass cleaning gear, thermal IR, and gas measuring equipment.

The easterly conditions prevailing when the team got there restricted their access to the summit area. This meant the West Rim camera couldn’t be replaced and they were also unable to make detailed gas measurements as planned. They could visit the other two cameras, clean them, and swap out the batteries. They also visited the larger fumarole, known as F0 and measured its temperature. This had increased about 9 °C and is now 190 °C.

Ash emission has ceased, however White Island is always capable of a new eruption at any time, without any useful warning. We continue to monitor the volcano for possible renewed activity. The Volcanic Alert Level remains at Level 1. The Aviation Colour code remains Yellow.

 Agnes Mazot

Duty Volcanologist

 

Media Contact:

Brad Scott  

(07 3748211)

Volcanic Alert Bulletin RUA 2016/09:

10:50 am Friday 30 September 2016; Ruapehu Volcano

Alert Status:
Volcanic Alert Level
 remains Level 1 (no change) 
Aviation Colour Code
remains Green (no change)

This morning, steam plumes have been visible above Mt Ruapehu’s Crater Lake. The lake temperature is now 37 ºC as part of a heating episode that began around 2-3 September 2016. No seismic or acoustic activity has been recorded this morning, indicating the steam plume was not generated by activity in the lake. The Volcanic Alert Level for Mt Ruapehu remains at Level 1 (minor volcanic unrest) and the Aviation Colour Code also remains unchanged at Green.

The active crater at Mt Ruapehu is occupied by Crater Lake. Crater Lake displays temperatures that typically range between about 15 and 40 °C and the phases can last between about 9 and 20 months. The lake cooled to a minimum of 12 °C in mid-August and then remained at 13-14 °C until early September when it started to heat again. Based on past experience, as the lake continues to heat up, more occasional steam plumes can be expected. This is often controlled by atmospheric conditions near the mountain.

There have been no local volcanic earthquakes or changes in the levels of volcanic tremor this morning on the GeoNet instruments at Ruapehu. GNS Science volcanologists continue to closely monitor Ruapehu through the GeoNet project.

 

Geoff Kilgour
Duty Volcanologist

 

Media Contact:
Brad Scott
Volcanologist 

phone 07 3748211

Volcanic Alert Bulletin WI 2016/12:
11:00am Monday 19 September 2016; White Island Vol
cano 

Alert Status:
Volcanic Alert Level
 is lowered to Level 1 (from Level 2)
Aviation Colour Code
remains Yellow (no change)

No further sustained eruptive activity has been observed at White Island. As a consequence the Volcanic Alert Level has been lowered to Level 1. The Aviation Colour code remains Yellow.

Observations over the weekend suggest no further sustained ash emissions have occurred from the active vents. Occasionally images on the web camera indicate very minor amounts of ash may be present in the steam plumes, but this has not been confirmed. Such intermittent appearance of ash is likely due to shedding of debris on the fumarole walls and may be expected to continue. The seismic and acoustic activity remains low, and the gas flux from the island has not changed substantially during this minor activity.

Although Tuesday’s eruption has ceased, White Island is always capable of a new eruption at any time, without prior warning. GeoNet continues to monitor the volcano for possible renewed activity.

Brad Scott
Duty Volcanologist


Media Contact:
Brad Scott
Volcanologist 

phone 07 3748211

Volcanic Alert Bulletin WI 2016/11:
12:15pm Thursday 15 September 2016;
White Island Volcano

Alert Status:
Volcanic Alert Level
 is lowered to Level 2
Aviation Colour Code
 
is lowered to Yellow 

Observations from a visit to White Island on Wednesday suggest that the minor ash emission that occurred on Tuesday 13 September 2016 has ceased. The Volcanic Alert Level is lowered to 2, and the Aviation Colour code is lowered to Yellow.

 Analysis of ash collected on Wednesday shows no evidence that Tuesday’s eruption was driven by new magma. Instead, gas flow dragged recently loosened material to the surface. Seismic and acoustic activity at remains low, and the gas flux from the island has not changed substantially since before Tuesday’s eruption.

Although Tuesday’s eruption has ceased, White Island is always capable of a new eruption at any time, without prior warning.

GNS Science continues to closely monitor White Island 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.


Steven Sherburn
Duty Volcanologist

 

Media Contact:
Brad Scott
Volcanologist 

phone 07 3748211

VOLCANIC ALERT BULLETIN: WI – 2016/10 

11:15 Wednesday 14 September 2016

Volcanic Alert Level 3 (no change)

Aviation Colour Code: Orange (no change)

Monitoring data available from the island confirms there has been no escalation in the level of activity and the emission of ash is currently very minor. 

The level of volcanic activity seen yesterday and overnight is very minor, with small amounts of volcanic ash being passively emitted from vent(s) within the active crater. We have reviewed all available data sets; seismic activity remains low, the gas flux remains low and there are no measureable acoustic signals. Some of our cameras are still affected by ash and steam, hence limiting our observations.

The poor light conditions and local high cloud make it difficult to assess the amount of ash present. It does appear the bulk of the emission was yesterday and only minor amounts are now present. Should ash emission increase today there is a low possibility of traces of ash reaching the East Cape area (based on weather and ashfall models).

The current activity is minor. We will review the situation if changes occur. Implications for visitor safety remain unclear. The Volcanic Alert Level remains at Level 3.

 

Steve Sherburn

Duty Volcanologist

 

Media Contact:

Brad Scott

07 3748211

VOLCANIC ALERT BULLETIN: WI – 2016/09

15:15 Tuesday 13 September 2016

Volcanic Alert Level 3 (no change)

Aviation Colour Code: Orange (no change)

As far we can tell from our monitoring data there has been no escalation in the level of activity at White Island since late morning. Seismic activity remains low on the island. Some of our cameras are now been affected by ash and steam, so we may not see much from them in the short term.

The level of volcanic activity seen earlier today was very minor, with volcanic ash been passively emitted from a vent on the 2012 lava dome.

The ash is visible on a NZ Metservice visible satellite image, which shows a plume extending offshore of East Cape. Any ash fall will follow wind direction and is likely to be blown offshore over the next day.

The current activity is minor. We will review the situation in the morning unless changes occur overnight. Implications for visitor safety remain unclear.

 

 

 

Steve Sherburn

Duty Volcanologist

 

Media Contact:

Brad Scott

07 3748211

VOLCANIC ALERT BULLETIN: WI – 2016/08

12:50 pm Tuesday 13 September 2016

Alert Status

Volcanic Alert Level 3 (change from Level 1)

Aviation Colour Code: Orange (change from Green)

 

The level of volcanic activity at White Island has increased late this morning with minor volcanic ash been passively emitted from a vent on the 2012 lava dome. A report from the island at 11.50 h has confirmed the ash emission.

The Volcanic Alert Level is now raised to Level 3, from Level 1.

The Aviation Colour Code is changed from Green to Orange.

The current activity is minor. We are unsure of the implications for visitor safety and will be issuing a further VAB later this afternoon (3 pm).

 

Steve Sherburn

Duty Volcanologist

 

Media Contact:

Brad Scott

07 3748211

GNS staff visited White Island (Whakaari) last week to continue their routine monitoring of the volcano and complete reinstating the levelling and magnetic networks. We also collected thermal IR images of the lava dome area, measured the Crater Lake level and temperature and fumarole temperatures. The Volcanic Alert Level remains at Level 1 (typical background levels).

Observations during this visit confirm the Crater Lake is reforming and growing. The April 27 eruption removed about 13-15 m of lake floor sediments and the new lake is forming at a lower level on the floor of the crater. The lake is currently about 28.4 m below the overflow level. Since 19 May the water level has risen about 3 m and the lake temperature has decreased as it gets larger. The temperature is now 52 ºC. The lake is now a light lime green colour, having changed from a milky grey shortly after the April eruption.

We are sometimes able to get Thermal IR images of a rocky lava mound in the back of the 1978/90 Crater and have established information on the very high temperatures that are present there. This is the same area where a lava dome grew in 2012. There are two areas of hot gas output and the temperature measurements ranged from 198 to 295 ºC. These are down on the measurements we made in August when they ranged 292 to 337 ºC in the hottest area. The temperature of Fumarole 0 (the largest accessible one) has changed little. We measured 170-173 ºC this time and 168-171 ºC last visit.

As we reported in May and June many of our survey pegs were sheared off or broken by the April eruption. This has had implications for the regular surveys we do like the levelling, magnetics and soil gas flux. We have completed reinstalling pegs and made the first magnetic and levelling surveys last week. Minor volcanic unrest continues.


The active vent-crater at Mt Ruapehu is occupied by a crater lake. Recently the lake has been cooling and we even discussed the possibility of new record low temperatures. The Crater Lake displays temperatures that typically range between about 15 and 40 °C. The lake has cooled to a minimum of 12 °C (15 August) but has now started to heat rapidly. GeoNet obtains temperatures from the lake using a data logger with a temperature sensor in the lake and communications via a satellite link.

In early August we discussed the possibility of the post 1995/1996 Crater Lake reaching a new low temperature as the lake was cooling strongly at that time. The lake reached a new minimum temperature of 12.0 °C on 15 August. For much of August the lake temperature ranged 13-14 °C, occasionally looking like it maybe going to turn and start heating. The temperature was starting to rise, very slowly, in late-August, but with quite a bit a lot of variability. However by 2 September a rising trend was clearly established. The lake temperature is now 17.6 °C.

On May 11 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. About 2 days after the lake temperature stared to rise on 2 September, the level of volcanic tremor also started to rise and has remained present since 4 September. The heating and cooling cycles are controlled by a mix of volcano and geothermal processes. 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.

 

 


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

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