[Vulkanen] The ring of fire #6: Waar diverse vulkanen puffen

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Santorini quake swarm continues- Greek media pick up news now
The highly unusual swarm of earthquakes SW of Santorini on the main fault zone that also defines the volcanic vents of the region continues with about 10 quakes larger than magnitude 2 during the past 24 hours. 2 of the quakes were magnitude 4 and 4.7, respectively.
Greek media start to pick up the story and become increasingly interested:

Today the wall of silence seems to be falling as a major Sunday newspaper has exclusive interviews with a number of Greek seismologists and geologists on the matter and some information is now public.

1. Inflation
From 1993 until 2010 there was deflation in the caldera of about 1cm/year, since the beginning of 2011 that has changed to inflation centered at a radius of 15 km on the north part of the caldera, rapid episodes of inflation have been recorded at intervals that coincide with bursts in seismic activity. Since August the intensity of the phenomenon warranted a rise to alert level 4 (red), where it has remained ever since.

2. Magma column
A displacement of 107 cubic meters has been located 1km north of the central island of Nea Kameni at a depth of 4 km, it is hypothesized that it is a magma intrusion, located right at the center of the most seismicity active part of the caldera.

3. CO2.
Co2 levels have jumped to 39 tonnes/day along with the emission of other gasses, a rising gas column has been observed outside the port of Thirassia in the caldera (the island on the west rim).

4. Water temperature.
The rise in sea water temperature in the caldera has been confirmed.

Most of the Greek scientists have brushed any concerns saying that conditions are normal and that has happened before, Euthimios Lekkas, geologist from Athens University, even said on TV that there is no danger even of a large earthquake in the vicinity of the island, the next day there were 3 earthquakes magnitude 5 and above, 50 km to the SW at the other end of the fault line.
Noticeable exception, foreign geologists have a very different opinion, Michelle Parks, a geologist from Oxford, mentioned that the evidence points to something important, there is volcanic activity and the volcano is now potentially active at depth.

Consensus is that the volcano has woken up in early 2011, but opinions differ mainly on the lines of nationality of the scientists.

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Semeru volcano alert status raised to level 3
A slight increase in activity of Semeru volcano's activity has been observed by the Indonesian Geological Survey in recent weeks and its alert level was raised to 3 (out of 4, "watch") on 3 February 2012, after it had been on level 2 since 16 July 2009.

Only small to moderate eruptions had been occurring over most of the past year. Between 29 December and 15 January, 8 explosions were counted which produced ash clouds up to 600 m high. One explosion threw incandescent bombs to a distance of 300 m from the Jonggring Seloko crater. During 15-29 January, only weak explosions were recorded and a small steam and ash plume rising 25-50 m was observed.

Between 30 and 31 January, 5 explosions were recorded. They produced incandescent fallout in up to 400 m distance. On 2 February at 07:47 local time, a stronger explosion produced incandescent bombs that reached 750 m distance and caused a small avalanche of blocks rolling down a distance of up to 2.5 km (note: no pyroclastic flows). The heightened activity triggered the raise in alert level the following day.

At its present status level of 3, PVMBG recommends to stay away at least 4 km from the summit on the SE side of the volcano and climbers are advised not to approach the Jonggring Seloko crater less than 1 km.
As of 6 February, no significant changes to its activity have been reported by our correspondent on location.

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Alertstatus Galunggung (Indonesia) raised
The alert status of Galunggung volcano in West Java, Indonesia, was raised today (Mon 13 Feb 2012) due to an increase of its water temperature and a change in color.

Discoloration of the crater lake had started to be noticed in September 2011, but the changes have increased recently. According to the local volcanologists monitoring the volcano, the whole lake is now of muddy khaki color. In addition to the color change which could be caused by an increase of lake fumarole activity, an steep sudden increase by 13°C of the lake water temperature was detected, based on measurements taken on and before 5 February when it was at normal 27°C, and on 8 Feb, when it was 40°C warm.
Most fish in the lake have died and occasionally dead birds are found at the shore.
No other signs of a possible volcanic awakening were detected at the moment. The ph level of the water is still at normal levels 7-8, and there is no sulfur smell. Also, no significant seismic activity has been detected.
Nevertheless, PVMBG has now placed the volcano at alert level 2 ("watch", on a scale of 1-4) and recommends to stay away at least 500 m from the lake shore.

The last eruptions of Galunggnug was a small phreatic explosion in 1984, and the major destructive eruption in 1982-83, which produced violent explosions with ash columns reaching 20 km height, pyroclastic flows and large lahars. The eruption destroyed an older lava lake, killed many people and displaced up to 35,000.
The eruption is infamous for the aircraft accident on 24 June 1982: a British Airways Boeing 747 with 262 people on board flew through the ash plume and had to make an emergency descent after the ash caused all 4 engines to fail; fortunately, the plane could land safely.

The present-day crater lake (Danau kawah Galunggung) has a diameter of 1000 m and is 11 m deep and contains a volume of about 8 million m3 of water.
In the middle of the lake, a small 250 x 165 m diameter scoria cone which was produced during the final staged of the 1982-83 eruption rises to 30 m elevation.
A main hazard of the volcano are phreatic and phreatomagmatic eruptions capable of draining the lake and producing mud flows.

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Nine small ash explosions at Fuego
Weak ash explosions continue at Fuego volcano. INSIVUMEH reported for 13 February that 9 eruptions were counted, producing plumes up to 500 m high and occasional rumbling noises. A steam plume is rising constantly about 100 m from the crater. The ash drifted 8 miles WSW.
The new lava flow on the southwest flank in the direction of the Taniluya ravine is still active and about 200 m long. Blocks that detach from its front form small block avalanches that reach the vegetation.

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Mt.Fuji Japan: Signs of unrest
Reports are appearing about unrest and signs of a possible awakening of Mt Fuji volcano in Japan.
According to a report which includes an unclear photo of the area, a row of new craters, the largest 50 m in diameter, has appeared on the eastern flank of the volcano at 2200 m elevation. Steam was observed erupting from these vents.

The observation joins other signs suggesting a gradual reawakening: A swarm of earthquakes including 4 of magnitude 5 have occurred northeast of Mt Fuji on and after 28 January. An earlier 6.4M quake occurred under the volcano on 15 March 2011. The report also mentions increased activity from a fumarole vent at 1500 m elevation and hot spring areas at the eastern flank observed since 2003.

These locations seem to be aligned geographically, and are probably connected. Dr. Masaaki Kimura of Ryukyu University is quoted to admit that there is an increased risk of and eruption on the eastern flank and that the status of the volcano should be closely monitored.

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New cracks in Canlaon Volcano crater Philipinnes
Three 50 m wide cracks have appeared on on the upper flank of Canlaon volcano (also spelled Kanlaon) near the crater after the M6.7 earthquake on Negros island in the Philippines on 6 Feb 2012.
According to PHILVOLCS, the Philippine volcano monitoring agency, the cracks were caused by the earthquake and are not likely a precursor for a new eruption, which would be the first since 2006, although Canalon is one of the country's most active volcanoes. A more detailed investigation is
planned and the mountain was for now closed for climbers.

Erik Klemetti on his more detailed post on Eruptions Blog mentions rightly that a major hazard from Canlaon volcano are landslides and mud flows, and that these are not necessarily related to an eruption, but can be triggered as well by heavy rain and gravitational instability caused by earthquake movements. In this context, the cracks should be examined and monitored carefully.

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New eruptions at Rincon de la Vieja Costa Rica
It has been almost exactly 14 years since the last eruptive period for Rincón de la Vieja in Costa Rica, but it looks like the volcano might be awakening from its break. Last Thursday (Feb. 22), the volcano experienced two small explosions in the early morning. Seismic records suggest the volcano also had small explosions on Feb. 19 and 20, according to the OVSICORI report for Feb. 25 (PDF). None of the explosions caused any damage to anything near the volcano and there are no reports of ash fall other than in the crater itself. These explosions are very similar in style to the September 2011 explosions that were like phreatic in nature — that is, not new magma but superheated water generated the explosions. Of course, it is likely that new magma intruding the volcano is the heat source for the water, but these explosions could precede a new magmatic eruption by months or years (or lead to nothing at all). The volcano sits within a national park in Costa Rica and after these explosions, the National Emergency Commission has declared the crater area off-limits to visitors.

The last major eruption from Rincón de la Vieja was in 1966, when it produced at VEI 3 event that generated pyroclastic flows. All the way back in circa 1820 B.C., the volcano produced the Río Blanco tephra from a larger VEI 4 eruption. The summit of the volcano hosts a small crater lake (see above), which could potentially add to the initial explosivity of any eruption as the water interacts with erupting magma. There are also abundant mudpots and springs within the national park as well, attesting to the persistent geothermal activity in the area. This geothermal activity is the reason why the Costa Rican government is looking to build a 200 MW geothermal energy plant in the National Park as well.

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Alertstatus of Ijen Volcano (Java) raised to 3 again
The official alert level for Ijen volcano in East Java, Indonesia, has been raised again to 3 ("alert") due to an increase in activity, our Indonesian correspondant Andi reports.
A new 10 m wide gas vent, which erupted buring gasses, was observed on 10 March at 17 m distance from the shore. Thick steaming, larger than usual, forming a thick white column of sulfur steam 200 m high was already noted since 3 March. Measurements of the lake water temperature at 5 m depth had also shown increased values of 42.70 deg C.

On 10 March, the lake surface was 2 meters higher than normal, although this could be attributed to heavy recent rain fall.

Another sign of increased activity is that many leaves of trees and other plants around the crater have died recently, suggesting higher than normal SO2 levels.

Seismic activity has been rising as well. Since 22 Feb, a near contiuous tremor signal has been being recorded. In the interval 22-31 Feb, there were 52 harmonic tremor periods lasting up to 20 minutes, as well as 17 2 low-frequency earthquakes, 38 mostly shallow volcanic quakes. This number increased to 306 tremor episodes lasting up to 25 minutes, 27 low frequency, and 125 mostly shallow volcanic earthquakes during the latest observation period between 1-10 March.

Ijen volcano in East Java, famous for its turquoise acid lake Kawah Ijen and the sulfur mine inside its crater, had been on higher alert starting 18 December 2011, but was lowered to alert 2 on 4 Feb this year, but is now again at the second highest level of 3, meaning that volcanologist think an eruption could be imminent. Access to the crater is currently closed.

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Smoke plume from Colombian volcano on Monday
MANIZALES, COLOMBIA (CBS) -- A rising smoke plume from a Colombian volcano put nearby cities and towns on alert as it continued to emit smoke, vapor and ash Monday.

The Nevado del Ruiz volcano, located in central Colombia about 130 kilometers (80 miles) west of Bogota, has been on yellow alert since October 2010 and began spewing ash and smoke last week.

The director of the Manizales seismic observatory, Gloria Cortes, said they are keeping a close eye on the volcano and monitoring seismic activity as they work with local officials to ensure the safety of nearby residents and tourists in the area.

"The local committee leaders, led by the area mayors, and given the current state of activity, have made a decision regarding the level of alert for the different areas and cities," Cortes said.

Authorities from cities in the volcano's proximity say they too are carefully watching the situation and have issued green and yellow alerts depending on how close they are to the volcano.

The mayor of Manizales, Jorge Eduardo Rojas, said his city is on green alert for now adding that could change if activity increases.

"Everyone needs to be ready for any situation. However, the city alert, which is at green, is still green and is not going to change though we are of course carefully watching for any changes on Nevado [del Ruiz]," Rojas, said.

Other cities closer to the crater are on an elevated yellow alert, though they say populated centers are not in imminent danger at the moment.

Thus far, the smoke plume has not caused any problems for air traffic.

The volcano's yellow alert means an eruption is possible though not definite. If it passes to orange it signifies an eruption is likely in weeks.

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More emissions from Mexican volcano
The Popocatepetl volcano registered 14 exhalations of low intensity accompanied by water vapor, gas and a low amplitude spasmodic tremor, reported the National Center for Disaster Prevention (Cenapred). In its latest report, the agency of the Ministry of the Interior (Interior Ministry) explained that the exhalations of greater intensity occurred yesterday 13:30 and 22:42 hours. He said that although during the night, a glow was observed in the crater, the other metrics do not show major changes, so the light status of volcanic alert remains at yellow stage two. Observers should expect more moderate exhalations, some with ash emissions, sporadic explosions are also likely to issue short incandescent fragments and slight glow in the crater can also be observed at night.

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Mexican quake may have triggered San Salvador volcano activity
The Mexican 7.4 magnitude earthquake near Acapulco on Tuesday might have affected the currently dormant San Salvador volcano in 1000 km distance and triggered an earthquake swarm under the volcano.

San Salvador volcano is an active stratovolcano immediately northwest of the capital San Salvador City and last erupted in 1917.

The National Service of Territorial Studies (SNET) reported that as of yesterday 21 March 05:30 pm local time, the swarm consisted of 25 quakes, including 8 felt quakes between magnitude 2.2 and 3.3. The quakes were located at shallow depths between 0.5 and 5.8 km under the volcano.
The Red Cross is reported to have sent some members to the volcano area as a precautionary measure, although there were no reports of casualties or damage.

It is possible that the strong Mexican earthquake was the trigger for this swarm as a result of tectonic disturbance of the magma chamber beneath the volcano. Relationships between large earthquakes and volcanic eruptions with effects occurring up to a year after the quake have long been suggested, but are difficult to proof.

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Vulkanen actiever bij volle maan
Italiaans onderzoek van de Stromboli heeft geleerd dat vulkanen actiever zijn bij Volle Maan. Dat meldt de website Geopersdienst.nl.

Aardwetenschappers Gianluca Sottili, van het Istituto di Geologica Ambientale e Geoingegneria in Rome, en Danilo Palladino, van de Sapienza-Universiteit in Rome, analyseerden de explosies die zich voordeden in de krater van de Stromboli van juni 2010 tot oktober 2011.

Eén uitbarsting per vijf minuten
De Stromboli bevindt zich even ten noordoosten van het eiland Sicilië in Italië, en is al minstens tweeduizend jaar continu actief. Gemiddeld eens per vijf minuten vindt er een uitbarsting plaats, aldus de website.

De onderzoekers concludeerden dat het aantal explosies per uur bij Volle of Nieuwe Maan significant hoger ligt dan het gemiddelde voor de hele maand. Maar bij springtij is er lang niet altijd een groter aantal per uur. In sommige maanden was de activiteit dan zelfs het laagst.

Ook uit eerdere onderzoeken aan andere types vulkanen blijkt dat de stand van onze natuurlijke satelliet de kans op een uitbarsting kan beïnvloeden. Hoe dat precies in zijn werk gaat is nog niet duidelijk.

Aantrekkingskracht van de Maan
De Italiaanse aardwetenschappers denken dat het gaat om de aanvoer van magma vanuit de relatief ondiepe magmakamer. Omdat het gesteente rondom het gangenstelsel waarin de magma zit door de aantrekkingskracht van de Maan elke veertien dagen een klein beetje wordt samengedrukt en weer uitzet, zal de magmatoevoer dezelfde regelmaat vertonen - en daarmee ook de frequentie van de uitbarstingen.

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Nevado del Ruiz seems to be getting closer to a new eruption.

INGEOMINAS reports that during the last week, there has been a significant increase in the activity of the volcano, which can be summarized as follows:

- From March 27, there have been phases of volcanic tremor pulses related probably to deep magma movements

- Since the last week, there were seismic signals interpreted with rock fracturing, i.e. dike intrusions, located west of the active crater. Similar seismic activity was observed prior to the eruptions in November 1985 and September 1989, although this time it is less energetic.

- On March 29 at 10:54 local time, for a period of 25 minutes, there were over 135 earthquakes located south of Arenas crater at a depth of about 4 km.
- From 04:00 am local time on 31 March, there has been a significant increase in seismicity of events associated with fluid movements and fracturing of rock located in the active crater.
- SO2 emissions continue at high levels.

According to the diagnosis made so far, INGEOMINAS expects an eruption in the coming weeks, but smaller in size than those in November 1985 and September 1989.

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Dangerous Colombian volcano may erupt soon
Colombia's snowcapped Nevado del Ruiz volcano has lately shown signs pointing towards an immanent eruption.

An "Orange" alert has been posted, meaning that the volcano could erupt within days to weeks, the Smithsonian/USGS Weekly Volcanic Activity Report web page said on Thursday.

The Andean volcano's last important eruptions happened in 1985 and 1989, the 1985 eruption having led to Colombia's worst natural disaster.

During the last week of March, tremors shook the volcano with increasing, according to the Colombian government agency, INGEOMINAS. Volcanologists interpreted the quakes as telltales for "rock fracturing" and "fluid movement" within the volcano.

Seismicity remained "elevated" during the first days of April, the report said.

According to the Smithsonian website, Nevado del Ruiz is spread over more than 200 square km (about 80 square miles) in central Colombia.

Standing more than 17,000 feet above sea level, the highest reaches of the volcano are clad in permanent snow and ice, the near-equatorial location notwithstanding.

The conflict between hot lava and ice on Nevado del Ruiz has proven deadly in the past.

During the November 1985 eruption, melting of the ice cap generated lahars, volcanic mudflows, which swept down the mountain's six main river valleys, the Wikipedia Nevado del Ruiz web page said.

A lahar following the Lagunilla Valley swept through the town of Armero, killing three-fourths of its 28,700 residents. In all, more than 23,000 people were killed and about 5,000 more were injured, according to Wikipedia.

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Alert level raised for 'Popo'
MEXICO CITY, April 17 (UPI) -- Mexico Tuesday advised residents of Puebla state to take further precautions as the Popocatepetl volcano continued to show ominous signs of life.

A Yellow Level 3 alert was posted for the area around the volcano Tuesday, meaning there was a intermediate or high probability of a violent eruption, which would range from an ash cloud to a possible explosion.

Schools were shut down in the area and residents were advised to stay inside and keep their windows closed to keep out the moderate amounts of ash that have been escaping from the mountain, CNN said.

Puebla state officials earlier evacuated a 7-kilometer (4.3 mile) perimeter around the mountain.

Scientists monitoring the volcano said Tuesday they saw glowing lava inside the crater overnight and recorded a 40-minute tremor.

Popocatepetl, known as Popo, is located not far from Mexico City and has not experienced a major eruption since 2000.