On June 12th, 1811, the British Navy ship HMS Sabrina was patrolling the Azores island
chain in the Atlantic as part of normal operations during the Peninsular War.
Suddenly, the relative silence was broken by a series of distant explosions.
Looking around, the crew quickly spotted a series of smoke plumes rising from the water.
This was immediately assumed to be the result of two ships firing with cannons at each other
as part of a battle.
Quickly sailing towards the smoke, the crew then realized that no battle existed there.
Rather, the sound of cannon like explosions was the result of a shallow submarine volcanic
eruption.
As shallow lava interacted with the overlying ocean water, it produced a series of powerful
explosions.
After anchoring away from the eruption at Ponta del Gada, the captain rode across part
of the island on horseback to get a safer view of the ongoing eruption.
He then observed the volcanic plume and clouds it quickly produced along with the nature
of the explosions.
Then, as the clouds above the eruption plume got larger and darker, and began slightly
rotating, something strange occurred.
A series of waterspouts suddenly formed, moving across the ocean surface.
Although not known at the time, what had just been witnessed was a tornado not generated
by a typical thunderstorm but rather completely from a volcanic eruption.
The volcano in question which produced the tornado was Sete Cidades, and this volcano
would continue to erupt for several more days.
So, how did a volcanic eruption create a tornado, and what types of eruptions would be best
for producing another tornado?
For context, I am specifically referring to true tornadoes in this video and not a separate
phenomena.
On occasion, whirlwinds develop within large fires or volcanic eruptions due to the intense
heat, creating what is known as a fire whirl.
While these phenomena can create a near continuous stream of fire and throw chunks of molten
rock long distances, they are not actually tornadoes.
While so called fire whirls can reach wind speeds of 120 miles or 200 kilometers per
hour, true tornadoes can reach wind speeds of up to 300 miles or 482 kilometers per hour.
While tornadoes occur around the planet, they most frequently occur in the United States,
which has on average 1,200 tornadoes each year.
Although tornadoes have occurred in all 50 US states, they most frequently appear east
of the Rocky Mountains and west of the Appalachian Mountains in the so-called tornado alley.
These tornadoes are generated by a rotating thunderstorm called a supercell.
Yet, not all tornadoes within the United States have been produced solely by severe thunderstorms.
For example, on August 15th of 2020 the Loyalton fire was burning out of control in California.
Due to the extreme heat of the blaze, it soon caused large masses of hot air to rise upwards,
while colder air traveled downwards.
Soon, a large group of pyrocumulonimbus clouds were created, which went on to generate not
one but two tornadoes.
The volcanic tornado which occurred at Sete Cidades originated under a similar circumstance.
For tornadoes to form, three things are needed; moisture, instability, and wind shear.
Due to the overlying water, large amounts of it flashed to steam and rose into the atmosphere
along with volcanic gasses.
Rising higher into the atmosphere, the warmer steam encountered a colder mass of air.
This interaction quickly formed a series of clouds, which continued to get larger and
larger.
As the energy in the clouds continued to increase, significant wind shear occurred, causing a
wall cloud to form and leading to the generation of a true tornado.
At shown by this example, while rare, volcano generated true tornadoes do occur.
They can technically form at any type of volcanic eruption, but are most likely to form during
a shallow submarine or surtseyan explosive eruption, as this eruption type naturally
ejects significant quantities of moisture into the atmosphere.
Similar eruptions in large water filled volcanic craters or caldera lakes could also produce
a tornado, but would be far less likely.
And, if an eruption was energetic enough, even one beneath a thick glacier whose plume
breaks through the glacier could also potentially generate a tornado.
Thanks for watching!
If you would like to request a specific topic, please leave a comment below.
Additionally, I would like to thank my new patron Nexhale for supporting this channel!