At the present, there are no warning signs that a supervolcano is about to produce a
large caldera forming eruption.
However, lets throw that aside for the moment.
Suppose a supereruption did occur.
Just how bad would it be?
What region of the world would become uninhabitable?
This video will outline a hypothetical eruption sequence if a theorized supervolcano in remote
Alaska was to produce a low end volume supereruption.
For context, supereruptions widely range in size and their volumes are generally measured
in terms of cubic kilometers of volcanic rock ejected.
A useful comparison is the 1980 eruption of Mount Saint Helens, which ejected one cubic
kilometer of material.
For comparison, supereruptions have ejected amounts of material ranging from 280 to 5,500
cubic kilometers of volcanic rock.
For our hypothetical supervolcano, we will have it produce a low end supereruption which
ejects 350 cubic kilometers of rock.
This supervolcano would be located around Mount Cleveland, which today is actually suspected
of being part of a supervolcano.
This supereruption would begin with a series of small phreatic explosions in areas of abundant
fumaroles, forming small craters.
As the alert level of the 6 adjacent volcanoes are changed from orange to red, something
strange occurs.
A curious fisherman who passes by notices a large group of bubbles rising to the surface
in a ring like shape surrounding the volcanoes.
Knowing that a major explosive eruption was imminent, a televised address was made, asking
all residents to get away from the coastline, leave islands in the Aleutians, and evacuate
the major cities of Homer, Kodiak, Juneau, and Anchorage.
After around 95% of the population in these areas left, a massive explosive eruption began
at three vents to the east of the Carlisle volcano.
As flights around the Pacific were immediately grounded, a plume of ash rose 40 kilometers
into the atmosphere.
Pyroclastic flows raced across the ocean, reaching nearby volcanic islands and destroying
all vegetation on them.
Then, the most powerful explosion ever recorded occurs.
A blast equivalent to the detonation of 800 megatons of TNT takes place as the majority
of Mount Cleveland explodes in an instant.
The blast wave produced by this explosion was so powerful, that anyone left at the nearby
town of Nikolski would be left permanently deaf.
This pressure wave would go on to be heard around the globe, and would circle the planet
several times.
This blast soon causes a massive landslide to occur as tens of cubic kilometers of rock
begins sliding into the ocean.
Upon impact, a megatsunami is generated.
Soon, a 250 meter or 820 foot high wave reached the town of Nikolski, wiping it off the map.
As the tsunami wave traveled up smaller mountains, it continued onwards.
Soon, the towns of Unalaska and Akutan would be destroyed by a wave more than 59 meters
or 194 feet tall.
While this wave would lose energy as it continued onwards, it would still have sufficient power
to generate destructive waves as far away as Anchorage.
While this was occurring, a plume of ash shot 50 kilometers into the atmosphere.
Near the eruption site, kilometer high pyroclastic flows raced across the ocean, travelling up
to 93 miles or 150 kilometers distant, and incinerating everything in their path.
As the eruption mushroom shaped plume expanded to the size of the continental United States,
it slowly drifted eastwards.
Soon, the west coast of both Canada and the United States would be shrouded in darkness
as the day seemingly turned to night due to the abundance of raining ash.
In Seattle, a half inch thick layer of ash would fall over the span of 48 hours.
In Juneau, roofs of poorly built structures begin to collapse, as a 4 inch thick layer
of ash continues to pile up.
In Anchorage, the situation would be far worse, as approximately a foot of ash would cover
the ground.
While this eruption would continue for another month, most of the ejected material would
be deposited in a span of 72 hours.
Due to falling ash, the tsunami, pyroclastic flows, and toxic volcanic gasses, the eruption
would end with 125,000 dead in the best of scenarios.
After the eruption ended, what used to be Mount Cleveland and the Tana volcanoes would
instead be a deep and 18 kilometer wide caldera.
Drinking water across much of the United States, Canada, and northern Mexico would no longer
be safe to use as it would be contaminated by fluorine via falling ash.
Over the next thirty years, temperature would plunge around the globe by 5 degrees Celsius
or 8 degrees Fahrenheit causing a volcanic winter.
Due to the abundance of sulfur dioxide in the atmosphere, crops would fail as only half
of the sunlight reached the ground.
Because of this, famines would spread around the globe, and wars in unstable nations would
pop up.
Luckily, there are no warning signs of such an eruption occurring at any supervolcano
such as Yellowstone or Toba anytime soon.
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