WHAT IS HAPPENING AT WHITE ISLAND VOLCANO??? New Zealand/Kermadec & South Pacific QUAKE/VOLCANO WATCH

K-Ar ages of some volcanic rocks from the Cook and Austral Islands

1U.S. Geological Survey, Menlo Park, California 94025
2Marine Physical Laboratory, Scripps Institution of Oceanography, La Jolla, California 92037
3Geological Research Division, Scripps Institution of Oceanography, La Jolla, California 92037
4Present address: (Jarrard) Department of Geology, University of California, Santa Barbara, California 93106; (Clague) U.S. Geological Survey, Menlo Park, California 94025.
Abstract

K-Ar age measurements on 19 volcanic rocks from Rurutu, Mangaia, Rarotonga, and Aitutaki in the Cook-Austral chain do not show a systematic increase in the age of the volcanoes to the west-northwest away from Macdonald Seamount as predicted by the melting-spot hypothesis and suggested by geomorphic evidence. Ages determined for alkalic basalt samples from Rurutu range from 1.02 to 1.09 m.y., for Mangaia from 16.6 to 18.9 m.y., and for Aitutaki from 0.66 to 0.77 m.y. Two distinct periods of volcanism on Rarotonga were dated at 1.8 and 1.2 m.y. B.P. The relation between the dated units and the main shield-building stage of these volcanoes is uncertain and will remain so until better data on the eruption history and mode of formation of volcanoes in the chain are available.

[link to gsabulletin.gsapubs.org]

According to Institute of Geological & Nuclear Sciences Limited (GNS) in a media release on 11 August, the Laboratoire de Géophysique (Papeete, Tahiti) reported that seismographs in Rarotonga recorded eruptive activity at Monowai seamount on 3 August. The activity then stopped overnight. See also the article we published on the massive amounts of pumice found in the greater Kermadec Islands area.

MVO reported that during 3-10 August activity at the Soufrière Hills (Montserrat) lava dome was mostly at a low level. The seismic network detected two small swarms of volcano-tectonic earthquakes on 7 and 8 August. Scientists at MVO observed a period of ash venting that began at 1700 on 8 August, less than two hours after the second swarm. Roaring sounds were heard at the same time. The ash plume drifted W over Plymouth at an altitude of about 1 km (3,280 ft) a.s.l., and a small amount of ashfall was reported by a fisherman offshore. The source of the venting appeared to be the gas vent in the floor of the 11 February 2010 collapse scar, and not the crater created on 23 March 2012.
On 9 August the inside of the collapse scar was partially visible during a helicopter flight. Fumarolic activity in the 23 March crater had increased compared to two weeks ago, and some other fumaroles were also more active. A change in wind direction shifted the volcanic plume N for much of the day and the odor of volcanic gas was noticeable in some inhabited areas. The Hazard Level remained at 2 (on a scale of 1-5).

as butterfly pointed out recently, we need to be watching the northland graphs, a lot of activity happening up there

[link to www.geonet.org.nz]

Thread: Japan aftershock upgraded to M7.4 — Gov’t now says it was 2 quakes at same time

hiya luis

yeah, i noticed that thread

also matrix had a thread about a possible paraguay quake that may have occured, but wasnt listed anywhere, here is the data from it:


2012-12-10 17:09:22.1 23.16 S 58.11 W 183 mb 6.2 A PARAGUAY BEO
2012-12-10 17:06 M THE
2012-12-10 17:06 M MCSM
2012-12-10 17:06 M LVV
2012-12-10 17:06 M BUC
2012-12-10 17:06 A MOLD
2012-12-10 17:05 10 M KAN
2012-12-10 17:00:13.0 24.58 S 4.87 E 10 mb 6.4 A SOUTH ATLANTIC OCEAN BEO

there is an unusual spike on the taupo volcano graphs

[link to www.geonet.org.nz]

i cant see any correlating spikes on any other nz volcan graphs

the closest is these spikes on the rarotonga ones, but they dont exactly match up
[link to www.geonet.org.nz]

4.1 05:28:06 Wed 12 Dec 2012 Depth: 170.1 km

3.2 02:54:52 Wed 12 Dec 2012 Depth: 101.4 km

3.7 02:46:16 Wed 12 Dec 2012 Depth: 337.5 km

Volcanic Alert Bulletin RUA-2012/05 - Ruapehu Volcano
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12 December 2012, 11:15 am - Ruapehu heightened unrest continues; Volcanic Alert remains at Level 1; Aviation Colour Code remains Yellow
Following a thorough review of recent monitoring data GNS Science has confirmed that it believes Ruapehu remains at a heightened level of unrest and that an eruption is more likely than normal.

GNS Science head volcanologist Gill Jolly said, “Our analysis is still showing higher than normal temperatures beneath the crater lake. We think this reflects a partially sealed zone a few hundred metres beneath the lake which might be causing a pressure build up behind it. That pressure would make an eruption more likely than normal.”.

“It doesn't mean that an eruption is inevitable”, said Dr Jolly. “If the sealed zone fails suddenly an eruption could occur, probably with little or no warning. If it fails more gradually then the pressure would probably be released more slowly and the likelihood of an eruption would revert to normal”.

“We never have the whole story so there is always uncertainty in our assessment of what might happen at volcanoes. It's like detective work without all the clues. But when we see something that might increase the chance of an eruption we have to be more cautious”, said Dr Jolly.

The crater lake is quiet and its temperature has remained relatively low, 20 - 25 degrees Celsius, since March. Our understanding of the situation is consistent with these observations.

GNS Science continues to closely monitor Ruapehu through the GeoNet project.

Background
Eruptions in 1988, 2006, and 2007 are believed to have occurred as a result of sudden failure of a seal beneath the crater lake.

Small earthquakes 3-5 km beneath the crater lake in late-October and early-November have now stopped. It is not clear if those earthquakes were related to the high temperatures estimated a few hundred metres beneath the lake.

GNS Science has a monitoring site at the crater lake which regularly sends back the temperature of the lake water.

The Volcanic Alert Level ranges from 0 to 5 and defines the current status at a volcano. Level 1 indicates a departure from typical background surface activity.

Aviation Colour Codes are based on four colours and are intended for quick reference only in the international civil aviation community. Code Yellow indicates that a volcano is experiencing signs of elevated unrest above known background levels.

Brad Scott, Steven Sherburn
Volcanologists

[link to info.geonet.org.nz]

Volcanic Alert Bulletin TON-2012/36 - Tongariro Volcano
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11 December 2012, 4:45pm - Prominent gas discharge at Tongariro, but no eruptive activity; Volcanic Alert Level remains at Level 1; Aviation Colour Code remains Yellow
Despite continued gas discharge that has been very noticeable over the last few days, Tongariro has not erupted since the explosion on 21 November. However, because of the current volcanic unrest a substantial possibility of further eruptions remains over the next few months.

GNS Science volcanologist Brad Scott said, “After the second eruption in November we now have to consider the possibility that Tongariro might have entered an eruptive episode and this unrest could continue for several months. Within an episode Tongariro might quietly discharge steam most of the time, but occasionally have small eruptions with little or no warning. There was a similar episode of activity in the 1890s”.

GNS Science head volcanologist Gill Jolly said, “There is still a lot we don't know about the recent activity and this means it is difficult to be certain what will happen over the next few months. Unfortunately with active volcanoes nothing is black and white and our best assessments still have a lot of uncertainty”.

“What we can say is that eruptions substantially larger than that on 6 August should give us some warning signs and at the moment we don't see any such signs ”, said Dr Jolly. In recent days GNS Science have received several reports of possible eruptions, but these have been normal steam discharge coupled with fine weather and light winds making for a prominent steam and gas plume.

There has been only minor seismic activity at Tongariro since 21 November, and no volcanic gas measurements last week due to poor weather and high winds. Gas may continue to be smelt downwind from Tongariro and be a minor irritant.

Background
The Volcanic Alert Level ranges from 0 to 5 and defines the current status at a volcano. Level 1 indicates volcanic unrest, with departures from background levels.

Aviation Colour Codes are based on four colours and are intended for quick reference only in the international civil aviation community. Code Yellow indicates that volcanic activity has decreased significantly but continues to be closely monitored.

Brad Scott, Steven Sherburn
Volcanologists

[link to info.geonet.org.nz]

Volcanic Alert Bulletin WI-2012/16 - White Island Volcano
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12 December 2012, 1:30 pm - Spiny lava dome – a new and unusual style of eruptive activity at White Island; Volcanic Alert is raised to Level 2; Aviation Colour Code changed to Orange

image at link
White Island showing a wide view of the active crater area. The lava dome is at the base of the prominent steam plume on the right side. The larger steam plume on the left side comes from a hot lake.

image at link
A close up view of the dome. The dome is made of thick, relatively cool and congealed lava and has prominent spines. The dome is about 20 – 30 metres across. In the foregrouond is a small, cold lake.

image at link
A compiled image showing the wide and close up views of the active crater area and the dome.
GNS Science volcanologists have noticed a spiny lava dome at White Island in an existing small crater formed as a result of eruptions in August. The Volcanic Alert Level has been raised to 2 and the Aviation Colour Code to Orange.

“On Monday we were able to see a spiny lava dome that has grown in a crater formed by an eruption on 5 August. We were really lucky the steam was not too thick and got great views. The dome is probably 20 – 30 metres across and has spines sticking up. In more than 30 years visiting White Island I've never seen anything like it”, said GNS Science volcanologist Brad Scott.

“If you imagine a volcano is like a tube of toothpaste then a lava dome is like the congealed, dried toothpaste that has come out of the tube. It doesn't move like a lava flow but grows from the inside as new magma comes up and pushes the already cooled magma upwards and outwards” said Mr Scott.

Comments from tour operators at White Island suggest the dome may have been visible for two weeks, but not as clearly as Monday. How long the dome has been growing is unknown, but possibly since the ash eruption in early August.

Lava domes are usually formed by magma that has lost most of its gases so that it is very sticky. This causes the magma to pile up over the volcanic event and form a dome. Lava domes are common at some volcanoes, but have never been seen before at White Island. Magma last reached the surface at White Island in 2000. At that time it was erupted explosively as molten rocks called volcanic bombs, rather than forming a dome.

“We've raised the Volcanic Alert Level and Aviation Colour Code to reflect the new style of eruptive activity”, said GNS Science head volcanologist Gill Jolly. “Our concern is that lava dome growth can be accompanied by explosive eruptions and could impact people on the island. We need to see if the dome is continuing to grow. If it's not growing then we will be less concerned”.

GNS Science continues to closely monitor White Island through the GeoNet project.

Background
The Volcanic Alert Level ranges from 0 to 5 and defines the current status at a volcano. Level 2 indicates minor eruptive activity.

Aviation Colour Codes are based on four colours and are intended for quick reference only in the international civil aviation community. Code Orange indicates that a volcanic eruption is under way with no or minor ash emission.

Volcanoes can erupt in many different ways. They can erupt explosively like Tongariro earlier this year when rocks and ash were hurled into the sky. They can erupt effusively with lava flows like Ngauruhoe in 1954 or in Hawaii. A lava dome is a type of effusive eruption.

Brad Scott, Steven Sherburn
Volcanologists

[link to info.geonet.org.nz]

White Island volcanic alert level raised

[link to www.nzherald.co.nz]

Lava Dome - John Seach

A lava dome is a mound of volcanic rock extruded from a volcano. The lava piles into a heap rather than flowing away. Diameters of domes range from a few metres to several kilometers. They can be up to 1000 m high.

Types of Lava Domes
1) Spiny domes (Pelean).
These are the steepest domes with a smooth surface and vertical spines.

2) Blocky domes.
These are composed of distince lobes which erupt sequentially from a vent.

3) Platy domes.
These have a low profile which is determined by local topography.

One of the main hazard from domes are explosions and collapse. Viscous lava in the dome can allow high pressure to build, resulting in explosive eruptions. Dome collapse under the weight of gravity can result in pyroclastiv flows, one of the most deadly types of volcanic eruption.

Causes of partial dome collapse include rain, gas overpressurisation, and over-steepening.

Examples of volcanoes with domes
Mt St Helens (USA), Merapi (Indonesia), Gunung Ranakah (Indonesia), Nigata-yake-yama (Japan), Nii-jima (Japan), Nipesotsu-upepesank (Japan), Augustine (Alaska), El Chichon (Mexico), Micotrin (Caribbean), Methana (Greece), and Soufriere Hills (Montserrat).

[link to www.volcanolive.com]

DESCRIPTION:
Lava Domes, Volcanic Domes, Composite Domes

From: Hoblitt, Miller, and Scott, 1987, Volcanic Hazards with Regard to Siting Nuclear-Power Plants in the Pacific Northwest, USGS Open-File Report 87-297
Volcanic domes are mounds that form when viscous lava is erupted slowly and piles up over the vent, rather than moving away as a lava flow. The sides of most domes are very steep and typically are mantled with unstable rock debris formed during or shortly after dome emplacement. Most domes are composed of silica-rich lava which may contain enough pressurized gas to cause explosions during dome extrusion.
The direct effects of dome eruption include burial or disruption of the preexisting ground surface by the dome itself and burial of adjacent areas by rock debris shed from the dome. Because of their high temperatures, domes may start fires if they are erupted in forested areas. Domes are extruded so slowly that they can be avoided by people, but they may endanger man-made structures that cannot be moved. The principal hazard associated with domes is from pyroclastic flows produced by explosions or collapses. Such pyroclastic flows can occur without warning during active dome growth and can move very rapidly, endangering life and property up to 20 kilometers from their sources. Such pyroclastic flows can also cause lahars if they are erupted onto snow and ice or incorporate water during movement.
From: Foxworthy and Hill, 1982, Volcanic Eruption of 1980 at Mount St. Helens: The First 100 Days, USGS Professional Paper 1249
Dome: A steep-sided mass of viscous (doughy) lava extruded from a volcanic vent, often circular in plan view and spiny, rounded, or flat on top. Its surface is often rough and blocky as a result of fragmentation of the cooler, outer crust during growth of the dome.
From: Miller, 1989, Potential Hazards from Future Volcanic Eruptions in California: U. S. Geological Survey Bulletin 1847
Volcanic domes are masses of solid rock that are formed when viscous lava is erupted slowly from a vent. If the lava is viscous enough, it will pile up above the vent to form a dome rather than move away as a lava flow. The sides of most domes are very steep and typically are mantled with unstable rock debris formed during or shortly after dome emplacement. Most domes are composed of silica-rich lavas that have a lower gas content than do the lavas erupted earlier in the same eruptive sequence; nevertheless, some dome lavas still contain enough gas to cause explosions within a dome as it is being formed.
From: Tilling, 1985, Volcanoes: USGS General Interest Publication
Volcanic or lava domes are formed by relatively small, bulbous masses of lava too viscous to flow any great distance; consequently, on extrusion, the lava piles over and around its vent. A dome grows largely by expansion from within. As it grows its outer surface cools and hardens, then shatters, spilling loose fragments down its sides. Some domes form craggy knobs of spines over the volcanic vent, whereas others form short, steep-sided lava flows known as "coulees." Volcanic domes commonly occur within the craters of on the flanks of large composite volcanoes.
From: Myers, et.al., 1997, What are Volcano Hazards?: USGS Fact Sheet 002-97
Molten rock (magma) that pours or oozes onto the Earth's surface is called lava and forms lava flows. The higher a lava's content of silica (silicon dioxide, SiO2), the less easily it flows. For example, low-silica basalt lava can form fast-moving (10 to 30 miles per hour) streams or can spread out in broad thin sheets up to several miles wide. Since 1983, Kilauea Volcano on the Island of Hawaii has erupted basalt lava flows that have destroyed more than 200 houses and severed the nearby coastal highway. In contrast, flows of higher-silica andesite and dacite lava tend to be thick and sluggish, traveling only short distances from a vent. Dacite and rhyolite lavas often squeeze out of a vent to form irregular mounds called lava domes. Between 1980 and 1986, a dacite lava dome at Mount St. Helens grew to about 1,000 feet high and 3,500 feet across.

[link to vulcan.wr.usgs.gov]

Dangers of Lava Domes


While one could easily outpace the eruption and growth of a lava dome, some extreme hazards do exist as the result of lava domes. When lava domes are growth rapidly and becoming unstable they will often collapse and spawn large and deadly pyroclastic density currents. In fact, pyroclastic flows due to lava dome collapse have been responsible for many of the largest volcanic disasters in history, including the 1902 destruction of St. Pierre on the island of Martinique. On May 8, 1902 the large and growing lava dome at Mount Pelée collapsed sending a large flow into the capital city of St. Pierre, killing all but two of the citizens.

This was scientists’ first experience with pyroclastic density currents, and while many lessons were learned that day, and have been learned since, people continue to be at risk from lava dome collapse spawned PDCs. Those especially at risk are scientists working near or on the volcano, and local community members whose homes could potentially be build on the flanks of an active volcano. It is imperative that we continue to try to understand lava dome dynamics so that we can better understand and work to mitigate the risk posed to people by lava dome collapse.

[link to www.google.co.nz (secure)]

Scientists keeping tabs on Ruapehu, White Island

[link to www.stuff.co.nz]

A rare "lava dome" has formed around the crater of New Zealand's most active volcano, as scientists raise the volcanic watch level on White Island.

A lava dome is when magma, which has lost much of its gas, bubbles out of the crater of a volcano.

It cools quickly and builds up from the bottom. GNS scientists likened it to "congealed toothpaste" found round the edge of the tube.

The Bay of Plenty volcano is New Zealand's most active and since a rating system has been in place, it has never rested at zero.

GNS today raised its alert level to two, indicating there had been minor eruptive activity.

Constant plumes of steam on the island generally made it difficult to see anything close to the crater, but GNS scientists said conditions on Monday allowed them to get a closer look.

Vulcanologist Brad Scott said he had "never seen anything like it" in his 30 years visiting the island.

"We were really lucky the steam was not too thick and got great views. The dome is probably 20-30 metres across and has spines sticking up."

It is thought the lava dome was a result of an ash eruption recorded on August 5.

Scientists also today confirmed Ruapehu remains at a heightened level of unrest and that an eruption is "more likely than normal".

GNS Science head vulcanologist Gill Jolly said analysis was still showing higher than normal temperatures beneath the crater lake.

"We think this reflects a partially sealed zone a few hundred metres beneath the lake which might be causing a pressure build up behind it. That pressure would make an eruption more likely than normal."

It doesn't mean that an eruption is inevitable, Jolly said.

"If the sealed zone fails suddenly an eruption could occur, probably with little or no warning. If it fails more gradually then the pressure would probably be released more slowly and the likelihood of an eruption would revert to normal."

Eruptions in 1988, 2006 and 2007 are believed to have occurred as a result of sudden failure of a seal beneath the crater lake.

"We never have the whole story so there is always uncertainty in our assessment of what might happen at volcanoes.

"It's like detective work without all the clues. But when we see something that might increase the chance of an eruption we have to be more cautious," Jolly said.

Small earthquakes 3 to 5 kilometres beneath the crater lake in late October and early November had now stopped.

GeoNet said it was not clear if those earthquakes were related to the high temperatures estimated a few hundred metres beneath the lake.

The crater lake is quiet and its temperature has remained relatively low, 20 - 25 degrees Celsius, since March.

First sighting responsible for undersea eruption
27th Oct 2012 5:00 AM

New Zealand scientists are investigating active undersea volcanos, north of New Zealand. New images reveal the impacts of a significant eruption on the seafloor.

NIWA research vessel Tangaroa has just mapped the Kermadec volcano that erupted 800 kilometres north east of Tauranga, on 19 July 2012, producing a pumice raft the size of Canterbury.

Tangaroa recently embarked on a 23-day voyage of discovery in the Kermadecs, north of New Zealand, to study the volcanic chain that stretches for 1000 kilometres north from Bay of Plenty.

"When we mapped the area yesterday", says NIWA ocean geology scientist Dr Joshu Mountjoy, "we found a new volcanic cone which has formed on the edge of the volcano, towering 240 metres above the crater rim.

"It is fantastic to be able to record the change on the seafloor following these kinds of events."

The Havre volcano eruption was strong enough to breach the ocean surface from a depth of 1100 metres. It produced clouds of ash visible by satellite, and a pumice raft that covered an area of 22,000 square kilometres.

The voyage, led by NIWA's volcanologist Dr Richard Wysoczanski, comprises geology and biology scientists from NIWA, GNS Science, as well as students from Victoria University of Wellington and The University of Auckland.

Dr Wysoczanski says, "One of the most exciting aspects of the cruise is the chance to map Havre volcano which, we have now confirmed, erupted in July. We know the shape of the volcano from previous research. Using the multibeam echosounder, we made a before and after comparison of the volcano to determine the size of the eruption and the change it has made to the seafloor."

NIWA had previously mapped Havre volcano in 2002, showing a 1 kilometre high undersea mountain with a 5 kilometre wide, 800 metre deep central crater. This central steep-walled crater is a caldera, which is a type of volcano, like Lake Taupo, known to produce large and violent eruptions.

amazing thermal image of havre volcano
[link to www.bayofplentytimes.co.nz]

Excellent Thread!! will be stopping in on a regular basis, Thanks for all your hard work!

hiya AC

thank you, and welcome aboard

this new development at white island is a surprise, to say the least..

White Island Volcano, New Zealand
John Seach on December 12th, 2012
On 12th December 2012 the alert at White Island volcano, New Zealand was raised to level 2 after a 20-30 m wide spiny lava dome was observed in a small crater. Tour operators on the island had noticed the lava dome for about 2 weeks. The dome possibly started forming after the August 2012 ash eruption. This is the first time a lava dome has been observed at White Island volcano.
More on White Island Volcano…

-----

White Island Volcano - John Seach

(Whakaari)
Bay of Plenty, New Zealand

37.52 S, 177.78 E
summit elevation 321 m
stratovolcano

White Island is currently the most active volcano in New Zealand. It is located 48 km offshore in the Bay of Plenty at the northeastern extremity of Taupo Volcanic Zone. White Island is unusual because its active subaerial vent is located below sea level.

White Island consists of an older eroded western cone, and a younger central cone that forms most of the island. The volcano rises 700 m from the sea floor.

The volcano has a history of frequent small phreatic and phreatomagmatic eruptions,
interrupting long intervals of continuous intense, fumarolic and hydrothermal activity. Historically active vents are located in the western subcrater and the western half of the central subcrater. Fumaroles and hot springs discharge on the floor of the main crater, and represent the subaerial expression of a long-lived acidic hydrothermal system related to the deeper magmatic system of the volcano.

The floor of the main crater is covered by a debris avalanche deposit, with a hummocky topography which formed by crater wall collapse in
September 1914, blocking a long-established vent system in the western subcrater.

Gases are continually emitted from the craters and fumaroles on White Island and pose a hazard to visitors to the volcano. Sulphur mining occurred at the island until 1914 when a crater collapse created a lahar which killed 10 workers.

2012 Lava dome
On 12th December 2012 the alert at White Island volcano, New Zealand was raised to level 2 after a 20-30 m wide spiny lava dome was observed in a small crater. Tour operators on the island had noticed the lava dome for about 2 weeks. The dome possibly started forming after the August 2012 ash eruption. This is the first time a lava dome has been observed at White Island volcano.
2012 Eruption
A small eruption occurred at White Island volcano at 04:55 am on 6th August 2012. The eruption occurred at the crater lake and was preceded by strong volcanic tremor on 4-5 August. The crater lake had gradually emptied during 2011 and 2012, and the water level rose rapidly 3-5 m on 27-28 July 2012.
2008 update
White Island's Crater Lake has continued to rise since December 2007, after being almost completely evaporated in late October 2007. By 23rd October 2008 the lake had risen by 15 m. New springs formed on the floor and old springs flowed again. Steam, gas, and mud emissions increased from the largest vent during October 2008.

1976-1982 Eruptions
The eruption sequence was the longest and largest historical event at the volcano. The eruptions consisted of seven phases of alternating phreatomagmatic and Strombolian explosions.
White Island Volcano Eruptions

2012, 2001, 1998-2000, 1998, 1995, 1986-94, 1983-84, 1976-82, 1974, 1971, 1971, 1970, 1969, 1968-69, 1966-67, 1962, 1959, 1958, 1957, 1955, 1947, 1933, 1930, 1928, 1926, 1924, 1922, 1909, 1908?, 1886?,1886, 1885?, 1885, 1856?, 1836, 1826.

images of john seach at white island
[link to volcanolive.com]

White Island volcanic alert raised

[link to www.rotoruadailypost.co.nz]

The volcanic alert level at White Island has been raised to 2 and the aviation colour code to orange.

GNS Science volcanologists have noticed a spiny lava dome at White Island in an existing small crater formed as a result of eruptions in August.

"On Monday we were able to see a spiny lava dome that has grown in a crater formed by an eruption on August 5. We were really lucky the steam was not too thick and got great views. The dome is probably 20 - 30 metres across and has spines sticking up. In more than 30 years visiting White Island I've never seen anything like it", said GNS Science volcanologist Brad Scott.

"If you imagine a volcano is like a tube of toothpaste then a lava dome is like the congealed, dried toothpaste that has come out of the tube. It doesn't move like a lava flow but grows from the inside as new magma comes up and pushes the already cooled magma upwards and outwards" said Mr Scott.

Comments from tour operators at White Island suggest the dome may have been visible for two weeks, but not as clearly as Monday. How long the dome has been growing is unknown, but possibly since the ash eruption in early August.

Lava domes are usually formed by magma that has lost most of its gases so that it is very sticky. This causes the magma to pile up over the volcanic event and form a dome. Lavadomes are common at some volcanoes, but have never been seen before at White Island.

Magma last reached the surface at White Island in 2000. At that time it was erupted explosively as molten rocks called volcanic bombs, rather than forming a dome.

"We've raised the Volcanic Alert Level and Aviation Colour Code to reflect the new style of eruptive activity", said GNS Science head volcanologist Gill Jolly. "Our concern is that lava dome growth can be accompanied by explosive eruptions and could impact people on the island. We need to see if the dome is continuing to grow. If it's not growing then we will be less concerned".

GNS Science continues to closely monitor White Island through the GeoNet project.

Scientists warn of unrest along New Zealand's North Island volcano belt

[link to www.globaltimes.cn]

New Zealand's central North Island looks set for a period of volcanic activity after warnings issued on three volcanoes over the last two days.

On Wednesday, scientists at the government's Institute of Geological and Nuclear Sciences (GNS Science) announced they had noticed a "spiny lava dome" that had grown in a crater on White Island, a volcanic island off the east of the North Island, after an eruption on August 5.

GNS Science raised the volcanic alert level to level two, indicating minor eruptive activity, and the aviation color code to orange, warning pilots that an eruption was underway with little or no ash emissions.

"The dome is probably 20 to 30 meters across and has spines sticking up. In more than 30 years I've never seen anything like it while visiting White Island," GNS Science volcanologist Brad Scott said in a statement.

"If you imagine a volcano is like a tube of toothpaste then a lava dome is like the congealed, dried toothpaste that has come out of the tube. It doesn't move like a lava flow, but grows from the inside as new magma comes up and pushes the already cooled magma upwards and outwards," said Scott.

Lava domes were common at some volcanoes, but had never been seen before at White Island, where magma last reached the surface in 2000 during an explosive eruption that threw up molten rocks called volcanic bombs, rather than forming a dome.

"Our concern is that lava dome growth can be accompanied by explosive eruptions and could impact people on the island. We need to see if the dome is continuing to grow. If it's not growing, then we will be less concerned," GNS Science head volcanologist Gill Jolly said in the statement.

GNS Science would continue to closely monitor White Island.

Also Wednesday, GNS Science volcanologists warned they still believed Mount Ruapehu, in the central North Island, remained at a heightened level of unrest and that an eruption was more likely than normal.

"Our analysis is still showing higher than normal temperatures beneath the crater lake. We think this reflects a partially sealed zone a few hundred meters beneath the lake, which might be causing a pressure build up behind it. That pressure would make an eruption more likely than normal," Jolly said in a statement.

"It doesn't mean that an eruption is inevitable," said Jolly.

"If the sealed zone fails suddenly an eruption could occur, probably with little or no warning. If it fails more gradually then the pressure would probably be released more slowly and the likelihood of an eruption would revert to normal."

The crater lake was quiet and its temperature had remained relatively low at 20 to 25 degrees centigrade since March.

Eruptions at Ruapehu in 1988, 2006 and 2007 were believed to have occurred as a result of sudden failure of a seal beneath the crater lake.

Small earthquakes 3 to 5 km beneath the crater lake in late October and early November had stopped, but it was unclear whether they were related to the high temperatures estimated a few hundred meters beneath the lake.

The volcanic alert level for Ruapehu remained at level one, indicating a departure from typical background surface activity, and the aviation color code at yellow, indicating signs of elevated unrest above known background levels.

On Tuesday, GNS Science warned that neighboring Mount Tongariro was still showing a substantial possibility of further eruptions after an eruption in August and two more last month.

"After the second eruption in November we now have to consider the possibility that Tongariro might have entered an eruptive episode and this unrest could continue for several months," Scott said in a statement.

"Within an episode Tongariro might quietly discharge steam most of the time, but occasionally have small eruptions with little or no warning. There was a similar episode of activity in the 1890s."

Tongariro had seen only minor seismic activity since November 21, but there had been a very noticeable gas discharge in recent days.

It was on volcanic alert level one and aviation color code yellow.

The 80,000-hectare Tongariro National Park has more than 1 million visitors a year.

Last month's eruption resulted in videos of panicked hikers fleeing from the plume of ash and steam.

Tongariro's eruption on Aug. 6 was the first since 1897.

Wow T!
Do you ever sleep? This is an amazing thread! You need an assistant! lol. Stay Safe Sis,prayers and

thank you, AK xxx

its only 8.42pm here, but i guess i will be busy tonight learning about spiny domes on my doorstep!

Nice new article about White island dome by Erik Klemetti
[link to www.wired.com]
The Strange Spine of New Zealand’s White Island
By Erik Klemetti12.11.1210:43 PM

The strange new White Island dome, peering over the ridge towards a cold lake in the volcano’s crater. The dome is ~20-30 meters across and may have been forming for the past two weeks. Image: GNS Science:
[link to www.wired.com]
...Now, that might be the strangest looking lava spine/dome I have ever seen. To give you a sense of scale, the GeoNet report on the spine says its ~20-30 meters across, so not that big. I’m not even sure how to describe it – the lava forming it has to be highly viscous and somewhat cool to form those strange spikes coming off the top. The color (yellows and reds) also suggests that the lava erupting has been pretty highly altered by hydrothermal gases (or that could have happened after the lava was extruded). Brad Scott from GNS Science said “in more than 30 years visiting White Island I’ve never seen anything like it.” It is truly weird – not only because domes are fairly uncommon at White Island.
The closest thing I can think of to this cold slug of lava is the famous whaleback plug that erupted during the 2004-08 eruptions at Mt. St. Helens. However, in that case, the dome was smoothed by the cold, viscous dacite lava dragging against the walls of the conduit. Here, it also seems like partially solidified, jagged lava was forced out of the conduit at the vent. This new activity has prompted GNS Science to raise the alert status at White Island to Level 2 with an Orange aviation code as new explosions could occur...

hiya AC

thanks for that article

Mount St Helens...

hmmm...

And link from comments for this article
[link to petrology.oxfordjournals.org]
...CONCLUSIONS

1.There is a clear pattern of volcanism over time on White Island, with major episodes of lava extrusion each probably separated by periods of phreatomagmatic or strombolian volcanism.

2.The White Island magmas probably all originate from enriched (metasomatized) mantle at or just above the slab–mantle wedge interface; the fluids come from the dehydrating slab. There is, however, good evidence for at least two separate source locations. Partial melts rise to a magma chamber within the crust where mixing and limited crustal contamination occurs.

3.High-Mg magmas rise rapidly from the main magma chamber as slugs or pockets of magma, which geophysical data suggest are <2 km beneath the active vents.

4.Prehistoric andesite and dacite lavas of White Island are also the products of eruptions from the same magma chamber, but have experienced different processes. The ‘dirty’ lavas with inherited phenocrysts result from interaction of the magma recharge with pre-existing crystal mush in the magma chamber. The ‘clean’ high-silica andesites–dacites are a product of filter-pressing of a more fractionated volatile-rich melt fraction.

5.Such multi-magma plumbing systems probably occur under most andesite–dacite arc volcanoes.

*Log Entry #244 Fri Dec 7 [21:31 UTC]
FRIDAY, 07 DECEMBER 2012 21:31
To view this video Log Entry please purchase a subscription

A deep earthquake recorded in the North Island Of New Zealand Today (166km) on Dec 7th, indicates a strong
meridian migration moving north which should produce a strong kinetic release into the Kermadec Islands Region
in the coming days. Possible locations for this event are:


Kermadec Islands Region (Raoul Island)
South Of The Fiji Islands
South Of Tonga


Forecast - (6.4-6.7 Magnitude)
Time Frame suggests December 8-10

*GNS Science Reports*
12 December 2012, 1:30 pm - Spiny lava dome – a new and unusual style of eruptive activity at White Island.
Volcanic Alert is raised to Level 2; Aviation Colour Code changed to Orange

[link to solarwatcher.net]

wow, heaps of info at this link