In the 20th century, there were a number of volcanoes which produced devastating eruptions.
Mount Saint Helens in 1980.
Santa Maria in 1902.
Mount Pinatubo in 1991.
Many of these eruptions are well known due to the catastrophic effects they had on human
life and the nearby environment.
However, one of the deadliest eruptions of the century has been long forgotten due to
the part of the world it took place in.
The volcano I am referring to is called El Chichon, which is located within Mexico.
In 1982 it produced a massive eruption which devastated the landscape in a 10 kilometer
radius, leading to more than 2,000 fatalities.
This video will discuss this volcano and mention what its future hazards are.
The El Chichon volcano is located in southeastern Mexico, where it is relatively close to the
border with Guatemala.
A major city close to this volcano is San Cristobal, which lies 90 kilometers to the
southeast.
The El Chichon volcano began forming 370,000 years ago, when magma related to offshore
plate subduction reached the surface.
Since the lava had a high viscosity, large quantities of gas could not easily escape
the magma which lead to numerous volcanic explosions.
During these eruptions, large rounded lava domes were constructed out of a gray rock
type known as trachyandesite.
These lava domes were periodically destroyed by larger eruptions, after which they would
then be rebuilt.
By 220,000 years ago, these overlapping lava domes had constructed a tall peak which likely
towered to 1500 meters above sea level.
Over the next several thousand years, a new complex of lava domes was constructed to the
northwest, before being destroyed in a large eruption which left a horseshoe shaped crater
in the landscape.
Then, 210,000 years ago, another large eruption occurred, but this time at the site of the
first group of lava domes to form.
This eruption completely destroyed the summit complex of El Chichon, leaving behind a 2
kilometer wide and 800 meter deep crater.
Over the next 120,000 years, numerous eruptions slowly refilled the hole left by the large
crater.
After a long period of infrequent eruptions, El Chichon became far more active beginning
12,000 years ago.
After the emplacement of another lava dome, eruptions began occurring to the southeast.
However, as seen by the giant crater in the ground, this newer eruptive center was destroyed
in another massive eruption approximately 8,000 years ago.
From 2030 BC to 1360 AD, a series of 10 large eruptions occurred, which created and destroyed
numerous lava domes within the summit complex.
Many of these eruptions were quite large, distributing ash as far away as Guatemala.
By the mid 20th century, El Chichon looked from the outside to be a dormant or extinct
volcano.
An old lava dome covered in numerous trees was its summit, which did not particularly
stand out in the landscape due to its small height compared to nearby mountains.
Then, beginning in 1980, a large swarm of earthquakes began in the region.
These earthquakes continued to escalate until El Chichon erupted on March 28th, 1982.
As the eruption began, it only continued to escalate, as trapped gasses underneath the
summit were released by intermittent explosions.
However, these explosions were not releasing a sufficient amount of pressure, causing an
even greater volume of combustible gas to remain beneath its summit.
Then, on March 29th, with little warning, the lava dome was instantly vaporized in a
massive explosion.
Pyroclastic flows soon raced outwards in all directions at speeds exceeding 200 kilometers
per hour.
These superheated flows destroyed all life in a 9 kilometer radius, leading to the destruction
of several towns.
As a continuous plume of volcanic material rose into the atmosphere, large volumes of
ash began falling across more than 24,000 square kilometers and burying crops by up
to 40 centimeters of ash.
Two more large explosions occurred on April 3rd and April 4th, after which the eruption
waned.
As the ash cleared, the summit became visible.
The summit lava dome had been destroyed, leaving behind a 1 kilometer wide and 300 meter deep
crater.
Since then, no additional eruptive activity has occurred.
Luckily, El Chichon is unlikely to erupt for sometime, as after individual eruptions it
typically takes between 100 to 600 years for another eruption to occur.
In the unlikely event it was to produce an eruption a bit sooner than expected, it would
require the evacuation of everyone in a 15 kilometer radius, totaling about 35,000 residents.
The main threat from this volcano are long distance pyroclastic flows, which have been
recorded travelling more than 10 kilometers away during individual eruptions.
With this being said, an extended evacuation radius would be needed for citizens up to
50 kilometers away who live adjacent to low lying points such as rivers and streams.
Any large rainstorm would wash away large quantities of ash deposited from an eruption,
generating a wall of debris in what is termed a lahar.
I hope that you enjoyed this video!
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