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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 

Overnight the GeoNet seismometer network in the Rotorua area recorded a swarm of small earthquakes near Lake Rotomahana. We have been able to locate 19 of the events. Their magnitudes ranged from M1.4 to M2.5, while the depths ranged between 9 and 5 kilometres.

Volcanologist Brad Scott commented that this is very typical of the earthquake activity in this area. Swarms are often characterised by no one main or large event, with many of the events being about the same size. Nine of the events in this swarm range M2.1 to M2.5. There are also many events too small to be located.

The events were too small to be widely felt or cause any damage. The two felt reports we have received indicate only weak shaking was experienced. 

 

Figure:  Mount Tarawera seismograph drum showing the earthquakes recorded last night.

 

Ruapehu: Crater Lake records lowest temperature since 2010

Crater Lake is currently in a cooling trend and has now reached below 15°C. This is the lowest temperature we have recorded from the data logger installed in April 2010. Since the lake was re-established in 1999, following its removal during the 1995-1996 eruptions the temperature has ranged from 13.5 to 60.8°C. Lake temperatures have been below 15°C on three separate occasions since 1999; 21 September 2004 (14.3°C), 15 August 2007 (13.5°C), and 8 September 2007 (14.0°C). These were manually measured during lake visits.

Since 1950, the temperature of Crater Lake ranged from 9°C in November 1988 to 60°C in April 1968 and May 1971. About 25% of the time the lake is cooler than 22°C and another 25% it is warmer than 37°C with an average of about 30°C.

Volcanologist Brad Scott said “regular temperature cycling of Crater Lake has frequently occurred since the early 1980’s. The current cycle is part of the normal behaviour of Crater Lake”.

Most eruptions from Crater Lake occur when it is hot, however some have also occurred from a cool lake. To put this in context, since 1965 there have been 35 eruptions through Crater Lake that have affected the wider summit area of Mt Ruapehu, only three of those came from cooler lakes (December 1979, December 1988 and September 2007). Hence it is very unlikely (9%) that an eruption of Mt Ruapehu affecting the wider summit area will occur while the lake temperature is less than 22°C.

Mt Ruapehu is an active volcano with a well-established monitoring regime in place. Our data indicates the lake is cooling, however there are still aspects of the heat flow and chemistry which indicate the vents are not sealed from the lake. Recent pilot observations also confirm some convection in the lake. 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

 

 

When Monowai, a submarine volcano 1500 km north-north-east of Auckland, is erupting it produces an unusual type of seismic wave called a T-wave. T-waves travel very efficiently in the ocean and those from Monowai are often recorded on a seismograph in Rarotonga, about 2000 km to the east. They are also well recorded by a seismic network in French Polynesia. Over the last few years we have learned to recognise the T-waves recorded in Rarotonga, and, with the help of observations from the RNZAF, commercial pilots and shipping, we are now reasonably confident we can identify when Monowai is erupting.

Submarine volcanoes are found all the way from New Zealand to Tonga. Monowai is about 1500 km north-north-east of Auckland, two-thirds of the way to Tonga, and is one of the most active submarine volcanoes in the south-west Pacific. The top of the volcano is only about 100 m below the sea surface.  Activity is occasionally seen from passing planes, but confirming eruptions has always been one of our challenges.

When erupting, the discharges from Monowai can discolour the sea, sometimes for several kilometres around the volcano.  Debris, pumice, foam and scum  are often present, but we get few chances to see these. Fortunately, the RNZAF and commercial flights do pass this area and we receive reports from pilots when they see any activity. The latest observations are from a RNZAF flight on 31 October and allowed us to confirm that our interpretation of the data from the Rarotonga seismograph is correct, and Monowai has been erupting. Monowai has actually erupted three times in October, each time for just a few days. The current activity appears to be weaker than we observed in 2009 and 2012.The recent visual confirmation of an eruption by the RNZAF is great as it gives us more faith in our interpretation of the Rarotonga seismic data. We are also able to share this with Maritime NZ and LINZ so they can keep shipping up to date on navigation hazards.

 

Brad Scott, Volcanologist

The lower levels of activity at White Island (Whakaari) allow for a more complete data set to be collected and confirms the volcano remains quiet.

Now that volcanic unrest has decreased we have been able to continue aspects of our routine 3 monthly surveys. These include hot spring sampling, soil gas measurements and ground deformation surveys. All surveys show values similar to the previous data, indicating a low level of activity continues.

No substantial changes in activity in the lake area or active vents were observed compared with previous visits. Volcanologist Brad Scott said: “It is great to be able to get a more complete set of data from the volcano and confirm the volcanic unrest remains at low levels. The last eruptions were in October 2013”.

During their visits to the island in late September, GNS Science staff measured the lake temperature (53°C) and that of fumarole F0 (149°C), on the southern part of ­the crater floor. These are similar to other recent measurements. The lake level is still rising slowly. Since the lake re-established in late 2013 we have measured a rise of about 2.5 m. For the first time in almost 2 years we obtained a sample of the Crater Lake water and our analysis shows no significant changes, from the old lake. The fluids in the new lake are similar to those we observed in the old lake from 2003 to 2011.

Several hot springs are sampled to see if the geothermal system is changing. The recent results show no changes. The soil gas survey showed no marked changes since the last survey in 2012. While the ground deformation survey shows a few mm of uplift across the crater floor since June.

The Volcanic Alert Level remains at Level 1 (minor volcanic unrest). Typical volcanic unrest hazards like hot ground and gas remain. A range of activity can occur under these conditions with little or no useful warning.

GNS Science is continuing to closely monitor the activity at White Island (and other New Zealand volcanoes) through the GeoNet project.

Contacts:

Duty Volcanologist: Steve Sherburn

Volcano information: Brad Scott

 

The GeoNet project is funded by EQC and provides monitoring for all of New Zealand’s volcanoes.

 To find out more about White Island, see here

Want to learn more about volcano monitoring, see here 

September was a busy month for earthquakes in the Taupo district. This is not out of the ordinary for this area and demonstrates the natural variability of earthquakes in this part of New Zealand.

The Taupo Volcanic Zone, which extends from Ruapehu in the south to Whakaari (White Island) in the north, has many small earthquakes occurring every year. Typically these are 3 to 12 km deep. This last month has seen a flurry of small earthquakes in the Taupo district. Some of the larger events, which were located closer to Taupo town, were felt by some of the local community. The two largest events occurred on 22 September and were both of magnitude 3.0, located at about 8 km depth in the vicinity of the Rotokawa geothermal field.

In total 55 small earthquakes were located throughout September in the Taupo district and they have clustered in three locations:

Although September was a little more busy than normal, the locations and size of the events are not out of the ordinary. This demonstrates the natural variability of earthquakes in this area. In the last year we located 342 earthquakes in the Taupo district. The largest was a magnitude 3.9 event at 10 km depth on 22 February 2014 near Motuoapa.

Mount Ontake’s recent eruption in Japan illustrates that while volcanoes are an important part of New Zealand’s recreation landscape, there are risks associated with these mountains.

“While we are interested in learning more about  Mount Ontake’s activity from a scientific perspective, more importantly, we send our deepest sympathy to the families, rescuers and scientists during this very difficult time. The eruption in Japan was a tragic example of what can happen on any cone (strato) volcano,” says Mike Rosenberg, GeoNet Duty Officer.

Examples of cone volcanoes in New Zealand are White Island, Mt. Ruapehu, Ngauruhoe and Mt. Taranaki


Aerial image of Mount Ruapehu.

While New Zealand has exceptional volcanic monitoring capacity, there is no guarantee that we will know when a volcano will erupt in the short term. However we regularly see aspects of volcanic unrest in the longer term at our active volcanoes. 

“Often, volcanoes let us know about ahead of time about eruptions by producing a swarm of small, shallow earthquakes that have unique energy signatures which can be identified. It is rare that a cone volcano will erupt without giving us a heads up first, but it has happened in the past decade in New Zealand,” says Rosenberg.

This occurred in 2007 on Mount Ruapehu.

From a volcanic perspective, the eruption on Mount Ontake came from a relatively small amount of magma, which on similar volcanoes can make prediction even more problematic.  Even small eruptions seriously affect people in close proximity to volcanoes and sometimes can make it extremely difficult to survive. 

 

If you are working on or visiting an active volcano you need to be aware of the local hazards and be prepared for these. Department of Conservation has advice for trampers/hikers in Tongariro National Park. 

(Posted 29/09/2014)

Volcanic Landslides

Volcano camera reveals some of its other secrets.

Images from our camera on the north rim at White Island are usually dominated by the vivid white gas and steam plumes from the active vents. What is less obvious is the source of the single largest natural event on the volcano in historic time - the 1914 landslide. This was more deadly than any eruption has been historically.

 

Around 9 or 10 September 1914, a large portion of the Main Crater wall at White Island collapsed onto the crater floor and consumed a mining camp. Sulphur was mined for the manufacture of sulphuric acid and fertiliser.  At the time this was headlined as “the greatest eruption in the Dominion since Tarawera on June 10, 1886” (Bay of Plenty Times 21 September 1914). Ten sulphur miners perished; the only survivor was the company cat, Peter the Great.  

The exact date and timing of the landslide is not well known. The island was visited by a launch from Opotiki on 15 September, however the launch master was not able to attract the attention of people ashore and could not land due to the sea conditions and darkness. He returned on 19 September. On landing he was immediately aware that a disaster had struck. He returned to the mainland and organised a rescue mission, but no trace of the miners was ever found.  An unusual cloud of ‘black smoke’ was noted from the mainland above the island on 10 September and this is thought to be ‘dust’ from the landslide and the most likely day of the event.

The source area of the landslide can often be seen in images from our web camera on the north rim and extends from the crater floor to the sky line. At the time of the 1914 landslide much of the Main Crater floor was covered by a crater lake, much larger than the lake there today.  The landslide came down into this lake, mixed with water and then flowed across the Main Crater floor and into the sea. The landslide has left hummocky mounds across the crater floor. The top of these mounds are great places to take panorama pictures of the island. Scientifically this is classed as a debris flow and the mounds are known as debris mounds. Similar deposits are found around many New Zealand volcanoes (especially  Ruapehu and Taranaki).   

Landslides are a common feature of White Island due to the high steep walls and weak nature of the material in the walls. The latest moderate size landslide occurred during heavy rainfall in July 2004, when a landslide off the north wall crossed half way across the crater floor. The landslide dammed some of the small streams on the crater floor. But this was very small compared to the 1914 one, only covering about 7% of the area of the 1914 one.

Gas flights have been completed at all of our active volcanoes this week.

The GeoNet volcano gas team like to make gas flights about once a month at our active volcanoes; White Island (Whakaari), Ruapehu and Tongariro (Te Maari). However the weather has a big say in this. This week we have had a great run of fine weather and the team has made measurements at all of our active volcanoes.

We mount our gas instruments in a modified Scenica aircraft operated by HeliPro. Some of the instruments ‘sniff’ the gas, while others look up through the plume.  At White Island we also have two permanent gas sensors (MiniDOAS) that give us addition data between the flights. You can find out more about the methods we use here or watch the video clip to see the team in action. We measure the amount of CO2 (carbon dioxide), SO2 (sulphur dioxide) and H2S (hydrogen sulphide).

On Monday Tongariro was flown, this is the most difficult one for us due to the topography around the vents, so we can not fly too close or low.  When the wind is from the right direction we can also mount our gas gear in a car and measure it by driving along the road under the volcano. Since the eruptions in 2012 the vents at Te Maari have been pumping out a lot of volcanic gas. The amount of gas has remained steady for the last year and a half; CO2 ranging 180 to 630 tons per day, while SO2 ranges 18 to 60 tons per day and H2S ranges 3 to 40 tons per day.

On Tuesday Mt Ruapehu was flown. The amount of gas from here is usually low and sometimes we can not detect the gases at all. It’s quiet different if the volcano is active and erupting, then it produces a lot of gas. The crater lake also has an affect, absorbing some of the gas. The amount of gas output since 2010 has typically ranged 50 to 2000 tons per day for CO2, while SO2 ranges 0 to 190 tons per day and H2S ranges 0 to 0.4 tons per day.

Then on Wednesday, a flight was completed at White Island. This is by far the easiest one to do as it always has some gas coming out of it and there are no other hills around.  White Island was active in 2012, when some small eruptions occurred. Since then the amount of gas has declined slightly. Recently the CO2 has ranged 1050 to 2600 tons per day, while SO2 ranged 360 to 2000 tons per day and H2S ranges 4 to 80 tons per day.

 


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