Posts Tagged ‘VEI5+’

Could Mount Agung eruption be the VEI 5+ volcano that is overdue?

October 16, 2017

We have not had a VEI 5+ volcanic eruption for 26 years since the Mount Pinatubo eruption in 1991. In 2015, I pointed out that the probability of a VEI 5+ volcano eruption within 5 years was over 95%. The probability of a VEI 5+ eruption in the next two years must now be approaching 99%.

(see also The next VEI 5+ volcanic eruption is overdue).

http://geology.com/stories/13/volcanic-explosivity-index/

It has been 24 26 years since the last VEI 5+ (Mount Pinatubo, 1991, VEI 6) occurred and the probability that a VEI 5+ volcanic eruption will occur within the next 5 years is now over 95%. There are around 10 – 14 VEI 5+ eruptions every hundred years and for the the last 300 years the time between eruptions has been as short as 1 year and as long as 23 years. The current gap could be the longest recorded in three centuries. There are, on average, 2 eruptions of intensity 6 every hundred years and so the probability that an eruption of VEI 6 could occur within 5 years is about 50% (current gap 24 years, average gap 50 years). That a supervolcanic eruption of VEI 7 or greater could occur within the next 5 years is less than 1%.

Mount Agung’s volcanic activity is now reaching levels which suggests that an eruption is “imminent”.

Volcano Agung in Bali is showing worrisome signs of a major eruption, writes German climate blogger Schneefan here. The highest level of activity with multiple tremor episodes were just recorded. You can monitor Agung via live cam and live seismogram.

The 3000-mter tall Agung has been at the highest warning level 4 since September 21.

Schneefan writes that the lava rise has started and that “an eruption can be expected at any time“.

So far some 140,000 people have been evacuated from the area of hazard, which extends up to 12 km from the volcano. Schneefan writes:

Yesterday ground activity by far exceeded the previous high level. Quakes have become more frequent and stronger, which indicates a stronger magma flow (see green in the histogram). Since October 13 there has been for the first time a “nonharmonic trembling (tremor), which can be seen in red at the top of the last two bars of the histogram.”

The colors of the columns in the bar chart from bottom to top stand for perceptible earthquakes (blue) low eartnhquakes (green) surface quakes (orange . Just recently red appeared, signifying non harmonic tremors.  The seismogram below shows what are at times longer period quakes: meaning magma is violently flowing in the volcano. Source: https://magma.vsi.esdm.go.id/.

Since yesterday the seismogram for AGUNG has been showing powerful rumbling (red).

The seismogram of AGUNG shows powerful tremors (level RED). The seismogram is updated every 3 minutes: Source: Seismogramm

Because Agung is located near the equator, a major eruption with ash flying up into the stratosphere would have short-term climatic impacts that could last a few years.

Agung last erupted in 1963 with an explosivity index of VEI 5, sending a plume of ash some 25 km into the atmosphere before leading to a cooling of 0.5°C. The eruption of Pinatubo in the Philippines in 1991 led to a global cooling of 0.5°C.


 

Mt. Sinabung lava dome now at 3.3 million cubic metres and still growing

June 15, 2015

Mt. Sinabung started erupting on 27th August 2010 after being dormant for 400 years. It has caused evacuations a number of times and has then quietened down only to start again a few weeks later. Lava flows have reached some 5 km from the summit on a number of occasions. 16 people were killed in early 2014. Mt. Sinabung gives the impression of building up for what could be the next VEI5+ volcanic eruption. One visual indicator is the size of the lava dome building up though it cannot be predicted as to how large a lava dome can get before it collapses. Multiple small collapses are much preferable to a single large collapse. But this lava dome has now grown to about 3.3 million cubic metres.

The shape and size of lava domes varies greatly, but they are typically steep-sided and thick. The thickness can range anywhere from a few meters to nearly one kilometer in height. The diameter or length of these domes can range from a few meters to many kilometers. The form that the dome takes is a function of many factors including strength and viscosity of the lava, as well as the slope of the land they are erupted onto.

On June 6th the lava dome at Mt. Sinabung was assessed to have reached 3.1 million cubic metres having grown around 100,000 cubic metres from the day before. Further assessment since then has been masked by cloud and smoke from the simmering and ongoing eruption. Yesterday “Sinabung spewed hot clouds reaching 3,500 meters to the south and 2,500 meters to the southeast.”

Wrath of Sinabung:: Burning lava streams from the peak of Mount Sinabung in Karo, North Sumatra, Thursday night. The volcano has been spewing lava 100 times a day since the alert was raised to the highest level on June 2, monitors say. (Antara/Zabur Karuru)

Burning lava streams from the peak of Mount Sinabung in Karo, North Sumatra, Thursday night. The volcano has been spewing lava 100 times a day since the alert was raised to the highest level on June 2nd. (Antara/Zabur Karuru) – Jakarta Post

Jakarta Post:

“In today’s eruption, Sinabung’s hot clouds simultaneously moved to the south and southeast. The hot cloud releases to the south reached 3,500 meters, or farther than the ones in the southeast, which reached 2,500 meters. This is because the lava dome is in the southern side of Mt. Sinabung,” Deri told The Jakarta Post on Sunday.

He said Mt. Sinabung still had a huge potential to erupt as the volume of its lava dome was still quite large.

“From the latest data, the volume of Mt. Sinabung’s lava dome has reached 3.3 million cubic meters. Eruptions previously occurred have not yet fully abolished its lava dome; thus, there is still a potential for massive eruptions,” said Deri.

Pyroclastic flows are caused by collapse of parts of the lava dome. On 14th June around ten flows were observed descending to the south-east and through the east-North-east channel.


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