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The shorts and t-shirt weather many have been experiencing may have been great for tan lines but the humid and cloudy conditions in the Bay of Plenty have not helped us with our monitoring flights for White Island (Whaakari). However yesterday the weather finally did allow for a monitoring flight to White Island.  The gas output from the volcano hasn’t changed much. This great weather also gave us unparalleled views of the Crater Lake, which also remains unchanged.

 

About our monitoring flights

We use several techniques to monitor and evaluate the volcanic gas output from White Island.

About once a month we plan to make airborne measurements of sulphur dioxide (SO2), carbon dioxide (CO2) and hydrogen sulphide (H2S) outputs from the volcano. The recent humid conditions in the Bay of Plenty have challenged us, however yesterday we made a successful flight.

To put some context around what White Island is currently doing, late last year the gas output averaged about 370 tons per day for SO2, 2100 tons per day for CO2 and 20 tons per day for H2S. During our flight yesterday (February 4) we measured 450 tons per day of SO2, 2100 tons per day of CO2 and 20 tons per day of H2S. These results are all very similar to our other recent measurements.

Two DOAS SO2 gas spectrometers are also installed on the island and under favourable conditions measure the sulphur dioxide (SO2) gas output. This has averaged around 300 tons per day in 2015, ranging from 120 to 750 tons per day.  During January- February 2016 it has ranged 180-670 tons per day.

We are crossing our fingers that the good weather holds for the next gas monitoring “fly by”.

Last week, we got a reminder about volcano hazards from the Tongariro eruptions in 2012. One of the stream valleys draining from near the Te Maari crater at Tongariro flooded, creating lahar-like conditions in the valley. Debris (sand, clay and rock) left over from the 2012 eruptions was remobilised by heavy local rainfall and washed out of the valley. Minor damage was done to a walking track.

Even though it’s been three years since the mountain erupted, moderate amounts of ash, sand and gravel remain as loose debris in the valley; it has never quite been cleared out. Due to the high intensity rain last week, the valley flushed out some more of this debris. We call this process remobilisation and refer to the floods as secondary lahars.

So when this stuff gets moving the consistency can range from that of muddy dishwater to that of thick wet concrete. Depending on the ratio of water to debris, within the flow there will be grain sizes from clay to boulders. This fluid has the potential to pick up much larger boulders and carry them down stream.  This type of flow can be quite damaging when carrying large boulders, so you want to make sure you and all your stuff are out of the way.

These secondary lahars are often referred to by volcanologists as the ‘sting in the tail of a volcanic eruption’. They can deposit volcanic ash and debris over large areas down slope and in river channels. Volcanologist Brad Scott points out we’ve seen several examples of these events in Tongariro National Park. Following the 1995/96 Ruapehu eruptions ash and debris was washed off the mountains for years and similar is now occurring at Tongariro following the 2012 eruption at Te Maari.

Depending on the consistency of the flow the scientists have several technical names for these (volcanic mud flow, debris flow or lahar). In all cases it is a mixture of water and volcanic debris that moves rapidly down off the volcano. For now, it looks like Tongariro is still capable of producing these secondary lahars when enough rainfall occurs.  Unfortunately the effects of the 2012 Te Maari eruption are still with us, albeit in a minor way. 

Since the 2012 eruptions, we’ve been keeping an extra close watch on Te Maari (Tongariro), installing extra seismic and GPS sites.  Although the activity has returned to background levels, the eruption has provided us with new research opportunities, particularly for our gas and geophysical scientists who want to further our understanding of what happens after an eruption. 

Over the past two years volcano geophysicist Craig Miller has been undertaking precise gravity measurements at Te Maari to detect changes to the volcano and hydrothermal system since the eruption.  The most recent of these surveys was completed last week. The gravity measurements show a positive increase in the local gravity field around the crater since the eruption.  This increase implies there has been a growth in mass or density of the rocks below the crater.

Coincident with the gravity changes new findings from satellite measurements show a small amount of subsidence or sinking of around 20 mm, per year (the length of a Pineapple Lump sweet) has been occurring in the Te Maari area since 2012.

Given this information, we think these changes are related to changes in temperatures and pressures in the hydrothermal or magmatic systems, specifically as the volcano is getting cooler and depressurising post eruption.   Both gravity and deformation data suggest changes are occurring at a depth of several hundred metres below the crater. Further analysis of the gravity data will identify the likely cause of these changes.

GeoNet continues to keep watching Te Maari closely. These repeat gravity and deformation check-ups help us understand more about the dynamic processes going on under the bonnet of Mt. Tongariro and supplement our standard volcano monitoring.


 

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VOLCANIC ALERT BULLETIN: WI2015/03
10:00am Thursday 10 December 2015; White Island Volcano

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

Recent routine monitoring of White Island (Whakaari) indicates minor volcanic unrest continues. In October GNS scientists reported an increase in the amount of volcanic gas been emitted and the presence of volcanic tremor.  This week we have completed soil gas and leveling surveys and a gas flight. The results of these surveys and other continuous monitoring confirms minor volcanic unrest continues at White Island.

GNS volcanologists who visited the Island this week measured minor amounts of ground deformation, ranging from +20 mm to -12 mm (over the last 3 months) and a small increase in the CO2 soil gas flux from 660-750 grams per square metre per day also in the last 3 months. There has been a small increase in the temperature of the hottest fumarole (174 to 177 ºC) in the last 6 weeks and the lake temperature (54-56 ºC). The water level of the Crater Lake has stabilised with no change noted on this week’s visit or by the regular measurements in the last 3-4 weeks. The SO2 gas output as measured by the DOAS SO2 gas spectrometers, has ranged between 250 to 680 tonnes per day of gas during the last month.

The levels of volcanic tremor continue to vary but do show a consistent rise over the last 2 months. They remain below those observed in 2012 when unrest was stronger and small eruptions occurred. The airborne gas measurements show a increase in CO2 output since the 18 November flight (2000-2200 t/day), while SO2 (400-340 t/day) and H2S (26-15 t/day) have declined.

The Volcanic Alert Level remains at Level 1 (minor volcanic unrest). The changes we are seeing presently are consistent with minor volcanic unrest. Activity may continue to increase or die away.  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.  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.

Volcano information:
Brad Scott
07 374 8211

Want to learn more about volcano monitoring?

http://www.geonet.org.nz/volcano/info/whiteisland

http://www.gns.cri.nz/Home/Learning/Science-Topics/Volcanoes/Monitoring-Our-Volcanoes or http://info.geonet.org.nz/display/volc/Monitoring+Methods

 

Volcanic Crater Lakes

In volcanic areas crater lakes are very common, some occupy depressions formed by lava flows damming valleys, while others are in craters formed during an eruption. The size varies from a few tens of meters across to tens of kilometres. Some are filled with cold ground water while others are warm or hot, heated by the underling volcanic processes. The colour of crater lakes varies markedly according to the temperature and chemistry of the water, and the type and concentration of particles suspended within it. Any reactivation or change in status of an active volcano is often reflected in the Crater Lake. This may be a chemical change, a temperature increase or water level variation. Many factors can influence a crater lake. It is these aspects of crater lakes that GeoNet takes an interest in.

Our interest in the Crater Lake is often shared with others depending on where the lake is and its past behaviour. At Mt Ruapehu that includes DOC and the Iwi, while in the large geothermal systems like Waimangu and Waiotapu it includes the Regional Councils, DOC, Iwi and the concession holders. At some of the lakes we have automated data loggers to collect data that is sent back to our data centres, or we use data from other agencies that already have monitoring in place. Often agencies support GeoNet as we have developed the technology to capture the information. This in turn makes information and data available to many end users. An example is the Crater Lakes at Waimangu.

The Crater Lakes at Waimangu were formed after the 1886 Tarawera eruption. Today they are some of the largest and most significant geothermal features in the Rotorua-Taupo area. This significance is recognised by the Regional Councils and no exploitation is allowed that could disrupt the lakes. This makes them perfect for monitoring. The BOP and Waikato regional councils share with GeoNet monitoring equipment in two of the lakes at Waimangu, while GeoNet also adds chemical sampling. Recently the councils have also established web cameras viewing Inferno Crater Lake and Frying Pan Lake using technology developed by GeoNet at Tongariro National Park and White Island.

 

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VOLCANIC ALERT BULLETIN: WI2015/02

White Island Volcano
Monday 2 November 2015, 2pm

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

Recent routine monitoring of White Island (Whakaari) suggests a slight decrease in the level of volcanic unrest. In October GNS scientists had measured an increase in the amount of volcanic gas emitted at White island. The increase of emitted gas also coincided with the presence of volcanic tremor.  The level of volcanic gas and tremor has declined slightly over the last week. This indicates a lower level of unrest at White Island. 

GNS volcanologists who visited the Island last week measured a small drop in the temperature of the hottest fumarole (170 to 162 ºC). There was no change in the lake temperature (54 ºC). The water level of the Crater Lake was falling but no change was noticed on this visit. The DOAS SO2 gas spectrometers ranged 350 to 520 tons per day of gas during the last week.

The Volcanic Alert Level remains at Level 1 (minor volcanic unrest). The changes we are seeing presently are common for the island. Activity may continue to increase or die away.  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 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.

Brad Scott
Duty Volcanologist


Media Contact:
Brad Scott
phone 07 3748211

 

Want to learn more about volcano monitoring?
http://www.gns.cri.nz/Home/Learning/Science-Topics/Volcanoes/Monitoring-Our-Volcanoes or http://info.geonet.org.nz/display/volc/Monitoring+Methods

Data from the GeoNet monitoring system at Mt Ruapehu underpins the lahar warning system operated by the Department of Conservation (DOC) and Ruapehu Alpine Lifts (RAL). The warning system is known as EDS (Eruption Detection System) - it provides an automatic warning to skiers when an eruption occurs. Lahars travel very fast and can reach the top of the ski areas within about 90 seconds of an eruption. The Whakapapa area is particularly prone to lahars from eruptions. The lahar warning system is complemented by education (posters, brochures, hazard maps), live tests on ski days, surveys of awareness, and training of operators.

The GeoNet monitoring system at Mt Ruapehu has recorded many signals during an eruption. Research funded by EQC, DOC and RAL has enabled the seismologists to develop a system that can identify an eruption from Mt Ruapehu. The system is based on identifying the earthquake produced by the eruption together with the airwave created when the eruption bursts through the Crater Lake. Hence the network of seismometers and airwave detectors operated by GeoNet is the core of the system. It has to establish the earthquake is from the volcano, and then confirm there is also an airwave at the same time. Once both of these parameters are confirmed the EDS is activated; the sirens and audio warnings on the ski area turn on to give the public warning. This is a world first.

The GNS Social and Impact scientists have also been studying the effectiveness of the education, training and responses to the EDS warnings. Observers during a live test document the responses of the skiers to establish how many ski to safety. Usually about 10% are left at risk during these tests. They also conduct surveys of awareness - what do people think are the correct actions. They find 30-40% are unsure of the correct actions. They have also developed a range of educational material in conjunction with DOC and RAL (brochures, posters, hazard maps), signs on lift tows ‘asking questions’ and repeating the key message ‘move out of the valleys’.

GeoNet and GNS Science have developed a series of videos related to our volcano hazards and how we monitor our volcanoes. These can be seen here.

YouTube videos about lahars and testing EDS can be seen here:

 

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Volcanic Alert Bulletin WI 2015/01 
9:30am Tuesday 14 October 2015: White Island Volcano

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

Recent routine monitoring of White Island (Whakaari) suggests a slight increase in volcanic unrest. GNS scientists measured an increase of CO2 in the gas emitted at the largest accessible fumarole (steam vent) on 1 October. These subtle changes also coincide with the presence of volcanic tremor and more elevated amounts of SO2 gas being emitted from the volcano. This indicates that unrest at White Island might have increased slightly over the past few weeks.

GNS geochemists sampled the largest accessible fumarole on 1 October. This sampling indicated a small increase in the temperature to 170ºC and an increase in the amount of CO2 gas; these are consistent with the other gas measurements we have made at White Island.

GeoNet uses several techniques to monitor and evaluate the volcanic gas output from White Island. Two DOAS SO2 gas spectrometers are installed on the island and under favorable conditions measure the sulphur dioxide (SO2) gas output. This has averaged around 300 tons per day this year, ranging from 120 to 750 tons per day during the last month. About once a month we make airborne measurements of sulphur dioxide (SO2), carbon dioxide (CO2) and hydrogen sulphide (H2S) outputs. This year these have averaged about 350 t/day for SO2, 1180 t/day for CO2 and 8.5 t/day for H2S. During our most recent flight on October 7 we measured 525 t/day of SO2, 1800 t/day of CO2 and 10.5 t/day of H2S. Both the SO2 and CO2 show increases.

Volcanic tremor is a common type of volcanic earthquake activity recorded on the island. Since 8 October this has been increasing in strength and become ‘banded’. This means that the volcanic tremor signal switches on an off every few hours, showing as bands across the seismic drum plot. Banded tremor is common at White Island and many active volcanoes worldwide. It has been recorded during increasing unrest and a variety of eruptive periods in the past.

During visits to the island in October, GeoNet staff have also sampled and measured the lake temperature (54°C) and it remains similar to other recent measurements. However the lake level has risen about 2 metres since June. Since the lake re-established in late 2013 we have measured a rise of about 6m.

The Volcanic Alert Level remains at Level 1 (minor volcanic unrest). The changes we are seeing presently are common for the island. Activity may continue to increase or die away.  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. 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.

Volcano information: Brad Scott
07 374 8211

 

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

http://www.geonet.org.nz/volcano/info/whiteisland

Want to learn more about volcano monitoring?

http://www.gns.cri.nz/Home/Learning/Science-Topics/Volcanoes/Monitoring-Our-Volcanoes

Lake Rotomahana sampling

On the 10th of June 1886 Mt Tarawera awoke from a short 600 year sleep, producing the largest historic eruption in New Zealand.  The eruption was short lived but very destructive. In a few hours a line of craters formed a rift over 17 km long, the famed Pink and White Terraces were gone and 106 locals had lost their lives. The eruption came in 3 phases; starting on Mt Tarawera the rift opened both to the north and south across the three summit lava domes (Wahanga, Ruawahia and Tarawera). Then followed the massive steam and lava eruptions from Rotomahana excavating new craters over 120 m deep in that area. The third phase was the creation of new craters in the Waimangu Valley area.

As part of the volcano monitoring in the area the GeoNet team samples the largest and hottest fumarole on the shore of Lake Rotomahana and two of the larger hot springs. Depending on the lake level these springs can also erupt as geysers. However as the lake level is down a couple of metres none of the springs are geysering at present. The fumaroles and springs are at boiling temperatures in this area. Another feature of the lake is the CO2 gas which diffuses through the lake from vents on the floor of the lake. The discharge has been measured at 550 tons per day, which is similar to Mt Ruapehu when quiet or less than half of White Islands current output.

 

There are many hazards associated with active volcanoes. Lahars are one of these and they can be very destructive.  A lahar is a type of mudflow or debris flow composed of slurry of volcanic material, rocky debris, and water. The material flows down from a volcano typically along a river valley.  Lahar is a Javanese word that describes volcanic mud and debris flows. There are three primary ways a lahar is formed;

1)    Volcanic eruption through a Crater Lake

This is very common at Mt Ruapehu. Many of the larger eruptions like those in June 1969, May 1971, April 1975, November 1977, December 1988 and September 1995 have produced lahars on Mt Ruapehu. The volcanic explosions expel the Crater Lake water onto the summit plateau and it then drains off the volcano as lahars in the valleys.

2)    Dam break

This occurs when debris from a volcanic eruption blocks up a river or lake outlet. The 1953 Tangiwai tragedy, where 151 people died after an express train fell into the Whangaehu River is an example. The outlet of Mt Ruapehu’s Crater Lake was blocked by debris from the 1945 eruption and this failed in 1953. A similar dam was created after the 1995/96 eruptions and that dam broke in March 2007. A large flood (lahar) was also recorded in February 1861, but we have no information about the source area. No eruptions were recorded at the time.

3)    Remobilisation of eruption debris

During a volcanic eruption ash and debris falls on the flank of the volcano. Then days, weeks or even months later heavy rain remobilises the debris and it is washed off the volcano.

Lahars can also be formed when snow and ice is melted by a volcanic eruption or a glacier breakout. In Iceland these are known as ‘jokulhlaup’. Lahars are able to flow large distances from the volcano and are very powerful. Lahars account for about 20% of the known fatalities associated with volcanoes in the world.

GeoNet and GNS Science have developed a series of videos related to our volcano hazards and how we monitor our volcanoes. These can be seen here.

GeoNet chemists, geologists and surveyors visited White Island last Thursday to take a soil gas survey, sample the Crater Lake, local hot springs and conduct a levelling survey. These tasks are part of the standard monitoring undertaken by GeoNet at White Island. The Crater Lake temperature was measured at 52.6 °C down from the 57.4 °C measured in June. The soil gas survey showed no change with 22 tons/day of C02 been measured, the same as in February 2015. Height changes measured by the levelling survey ranged from +32 mm to -19 mm compared to September last year (typical changes).  The temperature of Fumarole 0 (the hottest accessible fumarole on the island) was also measured, been 161 °C compared to 168 °C in June (basically no change). Overall the changes are minor and the volcano remains in a low level of volcanic unrest.

 

The monitoring at White Island is based around the 2 continuous recording seismographs and GPS that are complimented by the web cameras and a mini DOAS gas sensing network. Data from these permanent installations are supported by other data collected during regular visits, like last week.  These include spring and fumarole sampling, levelling for ground deformation, soil gas to measure the gas flux from the Main Crater floor and the temperature of the Crater Lake.

You can watch a video from a past trip below.

 

 

Nakadake volcano which forms part of the very large Aso volcano in southern Japan erupted at 9.45am on 14 September producing an eruption very similar to those from Te Maari in August and November 2012 and Ngauruhoe in the early 1970’s. The eruption was short lived and didn’t produce a very large ash cloud, similar to the Te Maari events. The other striking similarity is the production of what volcanologists call pyroclastic density currents (PDC’s), the most destructive near source volcanic hazard. They are a fast moving ‘current’ of hot gas and rock that normally hug the ground and travel downhill, or spread laterally under gravity. They are a common and devastating result of many explosive volcanic eruptions. 

The pyroclastic density currents (PDC’s) can be seen developing in the videos of both the Aso eruption and the 21 November Te Maari events (below). They also occurred in the 6 August 2012 Te Maari event but went unnoticed as it was dark. During the eruptions of Ngauruhoe in March 1974 and February 1975 they flowed down the flanks of the cone.

The 14 September eruption at Aso was preceded by small scale eruptions. JMA (Japans volcano agency) reported on 3 September a small-scale eruption that generated a whitish plume that rose 200 m above the crater and minor ashfall occurred. A white plume rose 400 m on 7 September.  Nakadake volcano is one of the most active volcanoes in Japan. Only the northernmost (Nakadake crater No. 1) has been active in the past 80 years, although some others were active before an eruption in 1933. The Nakadake No. 1 crater is occupied by a crater lake during its calm periods. Like Te Maari the Aso volcano is part of a National Park, however the summit crater of Nakadake is accessible by a toll road and cable car. Both are popular tourist destinations. 

Mt. Aso eruption of 14 September 2015.Te Maari eruption of 21 November 2012.

When the GeoNet volcano monitoring team outlines how they monitor a volcano they will mention seismic systems to record volcanic earthquakes and GPS to follow ground deformation. They will also mention gas and water chemistry and the behaviour of geothermal systems. One of the changes they look for is an increase in activity of the hot springs and geysers. If new magma (molten rock) is rising in a volcano it can add heat and fluids to a geothermal system. This will appear as more activity in the springs at the surface. There may be an increase in temperature, water level or cause over flow. There may also be a change in the chemistry of the fluids. Hence why we monitor these aspects of the volcanoes. Last week we responded to the reactivation of a geyser in Rotorua.

Geothermal systems are a by-product of volcanic activity. The heat from the volcano interacts with the local ground water to heat the water that is supplied to the springs and geysers at the surface. Hence we get lots a hot springs near our active volcanoes, especially in the Rotorua-Taupo area where we have some large volcanoes. They are known as caldera volcanoes. The large geothermal systems are also a source of energy and many are exploited for this. One of the consequences of development is the destruction of geysers and hot springs. For example, many features stopped after Wairakei was developed for geothermal electricity (over 100 springs and geysers stopped). Rotorua is another example, but there it was realised that the use was destroying the surface features and a bore closure programme was introduced to preserve the features.

The Rotorua bore closure programme by Ministry of Energy has resulted in many surface features recovering in the decade following the closures. Springs that had dried up have started to overflow again. Some had quite spectacular restarts and impacted the local environment. Hydrothermal eruptions can also be triggered during volcanic unrest. They were also a common feature in Rotorua during the active growth of bore use. There have been none since 2006 and this is attributed to the decline in bore use. Last week we had a geyser start erupting again in Rotorua. The GeoNet team visited to assess the activity and sample the fluid. The conclusion of their assessment is these changes are due to the bore closure programme, not volcanic unrest. Rotorua volcano has not had a volcanic eruption in the 50-70,000 years. 

About once a month the GeoNet volcano gas team make gas flights about our active volcanoes; White Island (Whakaari), Ruapehu, Ngauruhoe  and Tongariro (Te Maari). However the weather has a big say in this. Last week we have had suitable fine weather and the team completed a set of measurements at White Island (Whakaari).

The flight was completed at White Island on Friday using a float plane from Rotorua. White Island was active in August 2012 and August-October 2013, when some small eruptions occurred. Since then the amount of gas has declined slightly. Since the eruptions the carbon dioxide (CO2) output has ranged 950 to 1800 tons per day, while sulphur dioxide (SO2) ranged 170 to 610 tons per day and hydrogen sulphide (H2S) ranges 4 to 18 tons per day.  On Friday we measured a daily gas flux of 806 tons of CO2, 217 tons of SO2 and 10.4 tons of H2S. We also have two automated SO2 gas sensors at White Island and obtain 2-3 days of data each week from them. The SO2 output measured by them has ranged 106 to 675 tons per day. Last week’s data are typical of White Island.

White island is by far the easiest volcano for us to measure as it always has some gas coming out of it and there are no other hills around.  We can mount our gas instruments in two different aircraft types, the Cessna 206 or a Scenica aircraft. Some of the gas instruments ‘sniff’ the gas, while others look up through the volcanic gas 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).

 

 

 

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.

 


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

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