New Zealand volcanoes activity - White Island and Mt. Tongariro (July 31 until August 5, 2012)

This is Part 1 of the New Zealand volcanoes activity report

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Read also : (31/7 – 05/08)  – (06/08 - 07/08) -

This page is an archive page of activity reporting of the New Zealand volcanoes. As our main article becomes too long, we need to cut off some parts for easier reading and for Internet traffic bandwidth reasons.
Best Webcams : White Island Crater Rim and White Island Crater (1 image every 30 minutes) - Mt Tongariro (1 image every 15 minutes). If you know about a better one, please inform us and we will include it here


August 5, 2012

Small eruption at White Island Volcano

The White Island web camera has captured a small eruption on Sunday morning local time (August 5 04:55 am NZST or August 4 16:55 UTC) from the Crater Lake at White Island. During the past week there has been an increase in volcanic tremor and volcanic gas levels.
Overnight Friday July 27 to Saturday July 28 the lake level in the Crater Lake at White Island rose by about 3 m to 5 m. A volcanic earthquake was also recorded indicating an eruption may have occurred. A flow of gas and steam has been present through the lake and from vents near the lake since then. A gas flight on August 1 recorded increases of sulphur gases in the steam and volcanic gas plume.
Since early July there have been intermittent periods of volcanic tremor, becoming more continuous since July 28. A particularly stronger episode was recorded overnight August 4 - 5, and ended in a volcanic earthquake at 04:54 am NZST. Examination of the images from the Factory webcam between 04:54 am and 04:57 am on August 5 have revealed an eruption from the Crater Lake, nicely lit by the moon (see photo sequence below).
These phenomena are not unknown for White Island, but this is the first substantial confirmation that small scale eruptions are now occurring on the island and confirms the risk to visitors has increased.
White Island is an active volcano and there is always risk when visiting the island. Eruptions can occur at any time with little or no warning. We advise extra caution should be taken if visiting the island.
GNS Science volcanologists are monitoring the activity and further information will be released as soon as it is available.
The alert level of the volcano was raised from 1 to 2 (on a scale of 0 to 5).

Eruption at White Island on August 5 2012 - Image courtesy Geonet and GNS Science

 

White Island volcano New Zealand - RSAM and SSAM graph - image courtesy Geonet and GNS Science

Mount Tongariro volcano

The volcanic earthquakes continue beneath Mount Tongariro, but have declined in size and number. No other changes have been observed.
The sequence of volcanic earthquakes recorded at Mount Tongariro since July 13 has continued, but now there are fewer than 5 events each day and most are smaller than those in July (see graph below). Activity is currently at a lower level than in previous weeks, but may increase again at any time. The earthquake locations cluster in a zone beneath northern Tongariro (Emerald Lakes – Te Māri craters) at 2 km-7km depth.
No other changes have been observed. Initial analysis of the July gas samples confirmed that there had been a marked increase in the volcanic gas component of fumarole discharges at Tongariro. Full analysis of these samples continues.
We are planning field visits next week to retrieve data from the portable seismometers that were deployed across the mountain in late July. We also plan to repeat a survey of soil gas flux survey in the next few weeks. GNS Science volcanologists are monitoring the unrest and further information will be released as necessary.

Seismicity at Mt Tongariro - Image courtesy Geonet and GNS Science

 


August 3-4, 2012

New Zealands shaky attitude towards earthquakes and volcanoes
On Thursday, there was breaking news out of GNS Science after volcanologists determined that a recent increase in activity meant the aviation alert level needed to be lifted over White Island. The volcano’s alert level remains the same, but the increase in activity means pilots should be on a slightly higher alert in case a small eruption shoots ash and rock into the sky above this well offshore volcano. But this raised alert level follows hot on the heels from the decision to lift Mt Tongariro’s alert level up to one a couple of weeks ago, after a swarm of small quakes there. The two are unrelated confirms GNS. Read more …


August 2, 2012

Crater Lake at White Island has recently started to re-fill and gases are now vigorously streaming through it. Airborne gas measurements made yesterday show that the discharge of some sulphur gases has increased. During the past few weeks there has also been some minor volcanic tremor.
During 2011 and early 2012 White Island Crater Lake slowly evaporated to expose steam vents and form two large muddy pools. However, sometime between Friday July 27 and Saturday July 28, the lake level rose quickly by about 3 m to 5 m. Vigorous flow of gas and steam through the new lake can be seen from the air. Two photos at the end of this bulletin, taken from a similar position, clearly show the change in water level.

The lake has been inaccessible for many months and we have not been able to measure changes in its temperature or chemistry. Sulphur gases measured yesterday in the steam and gas plume have increased during the last three months but CO2 gas output remains at about the same level.
Since early July there have been intermittent periods of volcanic tremor, including several hours early on Saturday July 28 and during Monday and Tuesday this week. Tremor is not uncommon at White Island but earlier this year it had been at very low levels.
A recent ground survey showed that the main crater floor is no longer subsiding and now may be slowly rising.
These phenomena are typical for White Island’s activity, but are the first substantial changes to occur in the last few years.
White Island is an active volcano and there is always risk when visiting the island. Eruptions can occur at any time with little or no warning. The recent changes in activity suggest that the hydrothermal system has become unstable, and as a result the risk has increased. We advise extra caution should be taken, especially if approaching the Crater Lake and other active thermal features.
GNS Science volcanologists are monitoring the activity and further information will be released as soon as it is available.
The increased activity at White Island has no connection with the recent earthquakes and changes in gas flux at Tongariro volcano.
Alert Level remains at 1; Aviation Colour Code changed to Yellow
Image and text courtesy GEONET New Zealand and GNS Science


July 31, 2012

99 volcanic earthquakes since July 11 at Mt. Tongariro volcano, New Zealand

GNSC science volcanologist Michael Rosenberg published a rather extensive report on the current Mt. Tongariro volcano activity earlier today.

As part of our routine monitoring, we have recorded a sequence of volcanic earthquakes at Mount Tongariro since July 13, peaking in activity on July 20, and now numbering 3-10 per day, as shown on the graph below. The earthquakes cluster in a zone between Mount Tongariro and the eastern side of Lake Rotoaira at 2-7 km depth. These are very small earthquakes and unlikely to be felt by people.

To better understand the significance of these earthquakes and if volcanic unrest is developing at Mount Tongariro we have recently:

  • conducted more sampling of selected springs and fumaroles and completed some chemical analyses;
  • installed a GPS instrument to detect possible ground movement.

Analysis of the gas samples collected in the last fortnight shows that volcanic gas levels are above the normal levels measured at Tongariro. There is always a mix of volcanic and hydrothermal gases and fluids rising to the surface at Tongariro, but the recent samples contain a marked increase in the volcanic gas component. These results confirm the volcanic unrest indicated by the seismic data.

We are working to complete the analysis of the water samples and plan more field work within the next two weeks or sooner if activity changes significantly. GNS Science volcanologists are monitoring the unrest and further information will be released as necessary.

Mount Tongariro is a volcanic complex that lies to the north of Mount Ngauruhoe. It consists of numerous craters, cones and lava flows. Te Māri craters lie about two kilometers east of Ketetahi hot springs on the north side of Mount Tongariro. The Te Māri craters are the last craters to be active on Tongariro. Ash eruptions from Tongariro are recorded from 1855 to 1897, as well as unconfirmed activity in 1926-27.

Text and graphics courtesy Geonet and GNS Science

Rodger Wilson said in his daily volcano activity overview : Seismicity at Mt Tongariro volcano (New Zealand) has returned to low levels, but numerous small events are evident on seismic records there.


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