On June 12th 2022, at 3:37 am local time the Bulusan volcano in the Philippines produced
a new phreatic eruption, sending a plume of ash several hundred meters into the sky.
Over the next 18 minutes, the eruption continued, ejecting particles of superheated ash and
pulverized rock.
During this period, an interesting incandescent glow was noted to originate from Bulusan's
summit, where it was seen by many from its southwestern flank.
After the explosive phase of the eruption ended at 3:55 am, 6 vents which each originated
from a distinct crater on the mountain began emitting moderate amounts of ash.
These weak ash and steam plumes would later be seen once the sun rose, rising to a height
of 500 meters and drifting to the north and northwest.
By 9 am the ash emissions had ceased, and towns up to 50 kilometers distant from the
volcano had been covered in up to 3 millimeters of fresh ash.
What had just occurred was the 2nd phreatic eruption of Bulusan during its new eruptive
period which began on June 5th.
So, what will happen next?
Was the incandescent glow seen on Bulusan lava?
How long will its new eruption last?
This video will answer all 3 of these questions and discuss Bulusan's recent eruption.
For context, Mount Bulusan is located on the southeastern tip of the island of Luzon where
it is 54 kilometers southeast of Legazpi.
Bulusan is a more than 1,000 meter tall andesitic stratovolcano which is one of the most active
volcanoes in the Philippines.
It has erupted 14 times since 1978, where each eruption consisted of a single or group
of phreatic explosions, which are essentially large steam explosions.
They are caused when underlying magma directly or indirectly heats overlying groundwater,
causing it to flash to steam.
Since the mass of steam takes up more space than the water it once was it causes an immense
amount of pressure to build.
Eventually, this pressure is released upwards in an explosive manner, producing an eruption
which does not eject any lava.
Since record keeping began at Bulusan in 1852, it has not erupted a single fragment of lava.
Thus, the witnessed orangish red incandescence during Bulusan's latest eruption was not lava,
but most likely a symptom of volcanic lightning.
This lightning was generated when millions of ash particles collided with one another,
creating an electrical current which raced outwards in several directions.
The incandescence was thus likely the result of a lightning caused vegetation fire on Bulusan's
summit.
Although Bulusan's edifice has been uplifted by hydrothermal fluids, there is currently
no indication that a magmatic eruption is imminent as the movement of molten rock within
the volcano's magma conduit has so far not been detected.
Regardless, you might be looking at Bulusan's latest eruption and be confused as to why
its currently only rated as a 1 on the 0 to 5 alert level system.
This apparent low rating is not due to negligence, but rather has to do with how Bulusan is assigned
its alert level.
Not only do individual geological and disaster agencies have distinct rating systems, but
also many agencies give individual volcanoes differing criteria which must be met for a
raised alert level to be issued.
In the case of Bulusan, phreatic eruptions without evidence of a magmatic intrusion fits
the criteria to be designated as a 1 whereas the same scenario would cause Pinatubo to
be designated as a 2.
In the next several days to weeks, Bulusan will most likely continue to produce occasional
phreatic explosions interspersed with moderate degassing of the volcano.
Historically, the median eruption of this volcano lasted 40 days, but some eruptions
have lasted longer than 3 years.
There really isn't a good method to determine how long an eruption will last.
Based on the current emissions of Bulusan, its combined two phreatic eruptions would
most likely be classified as a 2 on the 0 to 8 volcanic explosivity index.
Bulusan's historic eruptions have ranged anywhere from a 1 to a 3, producing plumes up to 8,000
meters in height.
Thanks for watching.
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