On May 14th of 2023, the second tallest volcano in North America known as Popocatepetl in
Mexico began producing a dramatic spike in eruptive intensity.
Whereas beforehand 1 to 28 intermittent explosions would occur every week with this rate staying
mostly constant since the volcano reactivated in 1994, the number of explosions increased
in frequency, size, and in what is highly unusual for this volcano, created sustained
nearly 500 meter or 1640 foot high lava fountains that are more typical of a usually less explosive
stratovolcano such as Mount Etna.
By May 19th this intensity spiked again, causing so called vulcanian explosions to throw bombs
of lava more than 850 meters beyond Popocatepetl's summit crater, which then tumbled downslope
as lava avalanches for up to another 1500 meters.
This activity produced significant volumes of ash, causing 4 millimeters thick of material
to fall as far away as 45 kilometers from its summit.
I personally estimate that during the last 3 days alone, Popocatepetl has ejected 17.4
million cubic meters of ash and tephra, meaning its current eruption would rate on the 0 to
9 volcanic explosivity index as a 3.
All of this ash has resulted in the temporary closure of two major airports as ash is incredibly
potentially damaging for aircraft engines, while in addition caused schools to close
for tens of thousands of students on both Thursday and Monday.
Because of the dramatically increased intensity of this eruption, on May 21st 2023, Popocatepetl's
alert level was raised a tier on the local alert level system, now being a single tier
below what would in my opinion almost certainly trigger some evacuations.
This has triggered an influx of news reports claiming that millions of people are at risk
or that millions of people might need to be evacuated.
However, at least at the time of the writing of this video, those are gross exaggerations
in my opinion that assume a worst case scenario.
And yes, millions of people are at risk at the present if you are counting the number
of people that will be annoyed to remove ash from their building roofs and sidewalks.
With this being said, there is currently a 12 kilometer exclusion zone around Popocatepetl's
summit.
To best explain my analysis of the situation, you need to first understand the local volcano
alert level system used by CENAPRED.
This volcano alert level system has 7 tiers, with 2 being green, 3 being in yellow, and
2 being in red.
Green marks when the volcano is not erupting, yellow marks when it is erupting, and red
marks a major eruption which requires an evacuation.
Each tier has more than one "phase" which subdivide it in intensity, with a higher numbered
phase indicating a potentially more dangerous situation.
Popocatepetl is currently at an alert level of yellow, phase 3, which has only happened
at the volcano 4 other times in the last 20 years, marking the latest eruption as sort
of a once in a 5 year event.
The reason for this increase in sulfur dioxide emissions and ash emissions can be found by
simply the color of ash which fell.
Thus, I present ash which fell from Popocatepetl on May 20th on the right alongside ash which
fell from it on May 21st on the left.
The black represents highly unusual basalt, hence the darker color, while the gray ash
represents andesite which is the typical erupted composition lava at Popocatepetl.
This suggests that a preexisting basalt lava dome which had likely been built in the last
weak exploded on May 20th.
This dome likely formed due to a moderate volume injection of basalt magma from the
deep crust, hence the creation of tall lava fountains and higher than typical gas emissions.
Once the lava dome was mostly destroyed, more viscous andesite lava erupted, meaning that
the next few days to weeks might see larger explosions than witnessed in the past week
occur.
Yet, there is a legitimate concern at Popocatepetl.
It appears that lava domes are being repeatedly generated and destroyed over the past few
days.
There could reach a point where so much material builds in Popocatepetl's central crater that
a plug forms, eventually leading to a powerful eruption that if it were to occur would almost
certainly produce pyroclastic flows which would travel several kilometers.
A somewhat similar situation occurred in December of 2000, resulting in an 8 kilometer long
pyroclastic flow.
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