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  Moderator vrijdag 22 mei 2015 @ 09:27:48 #1
8781 crew  Frutsel
pi_152846631
Afgelopen week heeft de vulkaan Sakurajima (in Japan) zich weer van zijn beste (explosieve) kant laten zien.



quote:
A peak of activity occurred yesterday, with two strong explosions that produced ash plums that rose to 17,000 ft / 5 km altitude.
The activity was followed by continues, noisy smaller explosions and ash venting which lasted and slowly decreased during the night.
Today, two normal-sized explosions have taken place so far

After a very busy 17 May, with several strong explosions sending ash plumes to up to 16,000 ft (4.5 km) altitude, the volcano has been relatively calm during 18 and most of 19 May.
A filming team of VolcanoDiscovery being on location, we could observe hour-long phases of near-continuous mild to moderate ash venting. After approx. 10 hours of almost no visible activity, a probably strong explosion occurred yesterday night at around 11 pm, lasting several minutes, producing numerous lightning and heavy ash fall on the eastern sector. Cloud cover prevented detailed observations.

De vulkaan staat al langer bekend vanwege zijn vaak explosieve erupties die spectaculaire plaatjes/filmpjes opleveren, zoals deze


Meer vind je er ook hier:
WKN / Spectaculaire uitbarstingen vulkaan Sakurajima in Japan
pi_152864650
De vulkanen zijn erg actief de laatste jaren. Of lijkt dat zo?
pi_155320988
Vulkaan bij kernreactor Japan actiever

Een vulkaan in de buurt van een kernreactor op het Japanse eiland Kyushu wordt steeds actiever. De autoriteiten hebben mensen die binnen een straal van 3 kilometer van de vulkaan wonen zaterdag geadviseerd te vertrekken.

De vulkaan Sakurajima ligt op circa vijftig kilometer van de nucleaire reactor Sendai, die enkele dagen geleden opnieuw is opgestart door energiebedrijf Kyushu Electric Power.

Alle kerncentrales in Japan werden stilgelegd na de kernramp in Fukushima op 11 maart 2011. Door een aardbeving en de daaropvolgende tsunami ontstond een meltdown, waarbij de splijtstof en het reactorvat smelten. Het stilleggen kostte het land miljarden. Sendai is de eerste Japanse reactor die sinds de ramp in Fukushima is opgestart.
pi_155356622
quote:
The most recent radar measurements done by ALOS-2 satellite of the Japan Aerospace Exploration Agency (JAXA) show that the summit of the volcano has inflated by the enormous amount of approx. 16 cm during the interval 4 Jan - 17 August this year.
This suggests that a significant batch of new magma is currently stored in the volcano's upper plumbing system and the question remains when and how it might erupt. While surface activity at the volcano has remained very calm, authorities continue to prepare for the possible scenario of a major eruption in the near future. [less]
quote:
Activity has actually decreased and been relatively low at the volcano during the past days. However, the risk of a major eruption remains according to the Japan Meteorological Agency who maintains alert level 4 (preparation for evacuation).
http://www.volcanodiscovery.com/sakurajima/news.html
pi_155403634
quote:
Update
A pancake-shaped flat dome of lava has been detected inside the Showa summit crater. This type of dome is typical for moderately viscous and gas-poor lava (typically andesitic composition) extruded at subduction-zone stratovolcanoes.

The alert level of the volcano remains at 4 out of 5. One possibility is that the dome corresponds to older lava from the upper conduit that has been pushed out by a rising batch of fresher lava still inside the volcano.

Volcanic gas releases from sea floor detected

More worrying signs of volcanic unrest started to appear: according to FNN News, volcanic gas releases have been detected at the sea floor of the Futatsumata Port on the northern shore of Sakurajima peninsula (located approx 4 km from summit).
pi_155406794
quote:
Vent of Showa crater blocked - internal pressure rising

According to Japanese scientists, the scenario of a major eruption at the volcano is becoming more and more likely. The Asahi Shimbun news agency sent a drone to photograph the crater, confirming that a flat dome is currently blocking the conduit.
This blockage explains the near absence of explosions since mid July and suggests that internal pressure is increasing. The question is, simply put, when will it blow up and how much will come out?
Source: Blocked vent on Kagoshima volcano increasing likelihood of massive eruption (Asahi Shimbu
pi_155779404
quote:
Alert level lowered, no more deformation detected during 2 weeks

The alert level was downgraded back to 3 (out of 5) last Tuesday as signs of unrest and the risk of a sudden major explosion have decreased.

No rapid crustal movements have been detected since 17 August, suggesting that the inferred magma intrusion has stopped and is now stagnating & cooling instead of migrating further towards the surface.
The volcano continues to be unusually calm with only minor explosions and ash emissions occurring occasionally from the Showa crater.
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