Within Indonesia, one prominent volcano has been recently in the news for all the wrong
reasons.
The volcano in question is located to the northwest of the Toba supervolcano, and is
erupting from the same magma chamber which underlies the adjacent supervolcano.
The volcano I am referring to is called Mount Sinabung, which has been almost continuously
erupting since 2010.
Sinabung is a dangerous volcano, as its eruptions are unusually large.
Its current eruption has frequently produced pyroclastic flows, which have traveled across
the volcano, reaching up to 5 kilometers away.
This video will discuss this erupting volcano and mention what its future hazards are.
The Sinabung volcano is located in the northwest portion of the Island of Sumatra within Indonesia.
Specifically, it is 54 kilometers southwest of the city of Medan.
Before Sinabung began forming, volcanic activity had been ongoing in the region for several
million years.
This volcanic activity was due to two tectonic plates colliding southwest of Sumatra, where
the Indo Australian plate was being subducted underneath the Eurasian plate.
The melted crust from this collision then migrated upwards, but instead of erupting
on the surface, it collected in the crust.
This eventually led to four large volume eruptions at the Toba supervolcano, the last of which
formed a massive 100 by 35 kilometer caldera approximately 75,000 years ago.
However, despite the vast volume of magma which erupted, a supermassive magma chamber
remained.
This fed several lava dome forming eruptions, which occurred intermittently for 20,000 years
following its last caldera forming eruption.
However, since then, no eruptions have occurred at Toba.
This suggests that its vast magma chamber is erupting elsewhere and we finally know
where.
Although we aren't exactly sure when it began forming, much of this highly viscous magma
erupted at a young stratovolcano called Sinabung.
Recent studies of zircons found in some of Sinabung's lava flows have confirmed that
they originate from Toba's magma chamber.
As such, Sinabung could technically be considered an extension of the Toba supervolcano.
Regardless, by 34,000 years ago, Mount Sinabung had begun forming, as large volumes of lava
erupted onto the surface.
This lava deposited layer after layer of a gray lava called andesite.
Since this lava was highly viscous, it would often form lava domes during eruptions.
These lava domes would then collapse, sending large pyroclastic flows down the flanks of
the volcano.
Although we really don't know much about the early history of Sinabung, we can infer a
lot of data based on its recent eruptions.
Mount Sinabung appears to undergo a long term eruptive and dormancy cycle.
First, Sinabung would lie dormant for a period of several hundred to several thousand years.
Then, something would trigger magma to travel up through the crust into the volcano.
Initially, this would cause a series of phreatic eruptions, as heated groundwater in the volcano
flashes to steam and explodes.
Eventually, this magma would reach the main crater of Sinabung, and erupt in an explosive
manner.
Due to the high viscosity of the lava, it would build over the eruptive vent, before
being ejected by an explosion in what is termed a vulcanian eruption.
After several years to decades of high volume explosive eruptions, Sinabung would become
dormant once again, and thus the cycle repeats.
Before 2010, the last cycle of eruptions at Sinabung occurred in 810.
The eruptive series created a series of lava flows now overlaid by jungle which can be
found on the northwest of the volcano.
After a 1200 year dormancy, Sinabung erupted once again much to the surprise of locals
who had considered the volcano to be extinct.
Its first eruptive series in 2010 was largely phreatic, and resulted in minor damage in
the surrounding area.
After a three year dormancy, Sinabung erupted again in 2013 but this time with a large volume
of andesite magma.
This andesite has repeatedly formed lava domes, which get partially destroyed in vulcanian
explosions.
These explosions have largely sent pyroclastic flows to the southeast of Sinabung, although
they have traveled in all directions.
Using google earth, we can see the expanding area effected by these destructive pyroclastic
flows.
Although they have only traveled up to 5 kilometers away, I need to caution that 5 kilometers
is by no means a safe distance.
Given the type of lava erupted by this volcano, I say that pyroclastic flows can travel up
to 8 kilometers away.
As such, I recommend that the evacuation radius be increased.
As a final note, I caution residents to stay away from river channels whenever Sinabung
erupts, as the volcano has produced several large lahars.
Lahars are essentially flash floods filled with ash and other volcanic products.
They have swept away homes and bridges, and could effect areas up to 30 kilometers away.
I hope that you enjoyed this video!
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