Vaporized blood, crushed in an earthquake, being buried under tons of ash, or just being
cooked live in a flow of hot lava? How would a supervolcano actually kill you?
Defining a "supervolcano" isn't easy. The controversial term only
really took off after a 2005 docum-drama called
Supervolcano dramatized the aftermath of an eruption in Yellowstone National Park.
"This after all is not only how life ends, it's also how life begins"
Most volcanologists agree that a volcano becomes a supervolcano when it can potentially reach
level eight of the Volcanic Explosivity Index, or VEI. The second qualification
is if it can produce over 1,000 cubic kilometers of material, like volcanic ash.
Adding to the confusion is the fact that supervolcanoes are not bound to
erupt in devastating fashion. Broadly speaking, volcanic eruptions can be put
on a scale. Effusive volcanoes are relatively low-energy, like the ones that create large,
sloping shield volcanoes such as Hawaii's Kīlauea. Eruptive volcanoes have more explosive power, such
as the destructive Plinian-type eruptions, named after Romans Pliny the Elder who died in the AD 79
eruption of Mount Vesuvius, and his nephew Pliny the Younger, who later wrote about the eruption.
But what if the worst-case scenario happened today? What if an especially
large supervolcano, such as the one sitting beneath the Yellowstone caldera,
were to suddenly and explosively erupt? The consequences of this event
could be nothing short of disastrous and would affect humans the world over.
It's difficult to pin down the precise time that a volcano of any sort will erupt,
but certain precursors hint strongly at a coming blast. The movement of
magma toward the Earth's surface can produce telltale signs like bulging of the ground,
increased levels of volcanic gases, and odd temperature changes. Perhaps
the most dramatic precursor of all would be the earthquakes, and they wouldn't be mild, either.
Increased activity in a large reservoir of magma could spell more frequent and intense quakes,
especially as all of that melted rock moves closer and closer to the surface,
as U.S Geological Survey scientist Jacob Lowenstern told Vox. The tremors would also
serve to break up the ground above the entire looming magma chamber, making it easier for
the molten rock and pent-up gasses to reach the surface for miles around the volcano. Hopefully,
this would also afford scientists the opportunity to warn the public and get an evacuation moving in
time, though it would probably be a massive undertaking never before seen in history.
It's hard to say exactly how a blast from a supervolcano would turn out,
but things could get pretty spectacularly awful. The supervolcano currently sitting
beneath Yellowstone National Park is a good example. If that magma
chamber suddenly burst open, the shockwave emanating from the epicenter might kill
90,000 people alone, and that's before all of the actual volcanic material reaches them.
Smaller eruptions hint at the sort of shockwaves that a big one could produce. In January 2022,
a submerged volcano located within the territory of Tonga, named Hunga Tonga-Hunga Ha'apai,
erupted, causing a sound that could be heard from Alaska to New Zealand. While it produced a large,
deadly tsunami, the volcano also created a pressure wave so immense that it bounced around
the Earth for days. Speaking with The New York Times, physicist Mark Boslough compared the wave
to a staggeringly large sonic boom that encircled the planet, known to researchers as a "Lamb wave"
after mathematician Horace Lamb. Previously recorded Lamb waves came courtesy of nuclear
weapons testing. The last known volcano to have a similar worldwide effect was Indonesia's Krakatoa,
whose 1883 eruption was so intense that sailors on a British ship 40 miles from
the volcano suffered ruptured eardrums from the shockwave. The captain of that
ship wrote that the blast was so immense he thought that perhaps Armageddon had occurred.
Krakatoa offers up some of the best real-world evidence of what a larger
supervolcano might do to the hearing of people who
are nearby. Even witnesses thousands of miles away could hear the blast.
People typically reported that the eruption sounded like large artillery firing in the
distance. This is the longest a sound wave has been known to travel from its source to a
human ear. The Krakatoa eruption was incredibly powerful, spewing forth material at supersonic
speeds and obliterating its island. The tsunami generated by the explosion killed anywhere from
36,000 to 120,000 people. The sound alone still stands at the loudest noise ever recorded.
Despite all this, Krakatoa is not considered to be a supervolcano.
Its explosivity only comes in at a six on the Volcanic Explosivity
Index. While a supervolcano could erupt more quietly, such as with an oozing lava flow,
one that blasts forth as a violent Plinian eruption could be seriously loud.
Supervolcanoes are sitting on top of a lot of magma. Just how much depends on the volcano.
The Yellowstone caldera sits atop two large reservoirs of magma. The magma chamber closest
to the surface sits as little as three miles beneath the top and is an estimated 55 miles
long by 25 miles wide. Geologists originally estimated that only about 15% of that rock is
in melted magma form, but a 2022 study increased that number to about 20%. The lower magma chamber
is more than four times larger and sits between 12 to 30 miles deep, but just 2% of its reserves
appear to be melted. This still represents a tremendous amount of superhot molten rock,
but it might not be the massive underground cauldron of your worst nightmares.
Most estimates conclude that an Yellowstone eruption would produce more than a square
kilometer of lava. Though past lava flows have been fairly slow,
one in today's park would incinerate plants and buildings, cover roads,
and make it all but impossible to access parts of Yellowstone.
All of that lava, ash, superheated gas, and other material that can spew forth from a
supervolcano has to come from somewhere. And while a plume of toxic material hurtling into
the sky or along the slope is sure to catch your attention, there's also the
empty magma chamber left underneath the spewing volcano to worry about. During large eruptions,
that chamber quickly loses the support of the molten rock it once contained,
potentially becoming an unstable, hollow cave which might collapse in on itself. Anything on the
surface would be brought down in a catastrophic tumble, forming a crater called a caldera.
Sometimes, calderas fill with water, creating large lakes that people might not realize were
once the site of a humongous volcano. The Toba caldera in Indonesia is now a lake. In fact,
it's the largest known lake to have been formed by a volcano,
containing more than 58 cubic miles of water and reaching as deep as 1,656 feet. The biggest
caldera anyone appears to have found is underwater. Known as the Apolaki Caldera,
it sits in the Philippine Sea of the island of Luzon. It's estimated to be a staggering
93 miles across. The eruption that formed this beast occurred about 41 million years ago.
While there are plenty of things to worry about if you're in the path of a volcano, one hazard is
extra terrifying: pyroclastic flows. A pyroclastic flow is a mass of volcanic material, like ash,
rock, and gas, that comes barreling down the side of a volcano at intense speeds, ranging from 50
miles per hour, up to over 430 miles per hour. Because this mass of material is often dense and
can top 1,300 degrees Fahrenheit, anything in its path is pummeled and incinerated into oblivion.
This is exactly what killed most of the people who died during the eruption of
Mount Vesuvius. A 2018 study found that people sheltering in seaside boat houses
had been hit by a sudden and intense wave of heat soon after the eruption, followed by a
fast-moving pyroclastic flow. This was based on evidence left behind in skeletons, which showed
residue from the rapid vaporization of blood, which were preserved by a dense bed of ash.
A supervolcano could produce enough explosive power and material to create a pyroclastic flow
which could extend as far as 62 miles from the epicenter of the eruption.
Shockwaves, earthquakes, blasts of heat, and pyroclastic flows aren't all,
though. And relatively speaking, those threats don't even make it that far.
Not so for the ash produced by a supervolcano, which can be blasted high into the atmosphere,
allowing the material to spread out over a massive range. Volcanic ash
also contains sharp bits of material, making it tough and mildly corrosive.
Because it becomes conductive when wet, ash can also disrupt electronics.
The sheer amount of ash can be a big deal. An eruption of the Yellowstone
supervolcano could produce so much ash that structures as far as 60 miles away
would collapse under the weight. The fine ash can enter air filters and vehicle engines,
complicating evacuation efforts and attempts to bring supplies into the region.
According to a 2014 study published in Geochemistry, Geophysics, Geosystems, evidence
of ancient Yellowstone eruptions indicates that volcanic material made it as far as the Gulf of
Mexico. Depending on the length and intensity of a future eruption, practically everyone in the
United States and its neighboring countries would be dealing with the widespread and disruptive ash.
In addition to covering everything and ruining machines, volcanic ash can irritate your upper
respiratory tract and can present serious problems for anyone with pre-existing breathing
conditions. Very fine ash with a high silica content can present an even bigger and more
long-term breathing problem, as it can scar lung tissue and lead to a disease known as silicosis.
"...it's not ash from your backyard barbecue. It's rock.
It's abrasive. It's pervasive. It's destructive."
That's not all. It can also irritate the eyes and skin of sensitive people. And then there's
the problem of sulfuric acid, which can be produced when water in the atmosphere binds
with volcanic sulfur dioxide gas. This can lead to a decrease in air quality that could set in
motion long-lasting health issues. According to a 2019 study published in Epidemiology,
the late 18th-century eruption of Iceland's Laki volcano set into motion a complicated series of
events that lowered temperatures and increased levels of air pollution for Europe and beyond.
Pregnant people appeared to have been put under greater stress by the results of this eruption,
leading to a lower birth rate and greater infant mortality in Sweden for years after the eruption.
And then there's the mud, which can't be taken lightly.
"The Parks Service says lahars are the number
one volcanic hazard that can affect people living below Mount Rainier."
Known as a lahar, the mixture of water and volcanic debris that is produced by an eruption
can move downhill in excess of 100 miles per hour, becoming larger as it goes by collecting
more material. Depending on the landscape, a volcano can trigger a lahar by eruption beneath
or near a lake, or by melting ice and snow on its peak. Rainfall soon after an eruption can also
form fine volcanic ash into a lahar. The threat of a lahar can last long after the eruption,
as the changed landscape may not be able to contain rainfall and debris as it once did,
resulting in regular flooding and recurrent lahars. These mudslides can crush buildings,
block roads, and kill anyone who is unlucky enough to be in the way.
A supervolcano eruption could be so mighty that it could drastically change that of
the entire planet. The 1991 eruption of Mount Pinatubo in the Philippines shot an estimated
15 million tons of sulfur dioxide into the upper atmosphere. For the next two years,
those volcanic gasses reflected and absorbed sunlight, contributing to planet-wide cooling
by about one degree Fahrenheit at its peak. Dramatic as that effect was,
Pinatubo is not considered to be a supervolcano, only reaching six on the VEI. A sufficiently large
eruption of the Yellowstone supervolcano would likely have an even more noticeable
impact on the global climate, though it's hard to say precisely what it would do.
The lowered temperatures created by an atmosphere loaded with volcanic ash and
sulfur dioxide could harm agricultural production and put food insecurity and
famines at the top of everyone's mind. Toxic acids like Hydrogen halides produced by an
eruption can also damage food crops and put a dangerous dent in the global food supply.
While a supervolcano might contribute to global cooling, sometimes called a volcanic winter,
an eruption might also strip away other parts of our atmosphere. A 2021 study published in
Communications and Environment concluded that the Toba supervolcano eruption, which took place about
74,000 years ago, stripped a considerable amount of ozone out of the atmosphere.
The culprit? Volcanic gases like hydrogen chloride, which can disrupt the formation
of ozone, and provide a surface for ozone-busting reactions to take place.
Atmospheric ozone is kind of a big deal. When it sits high in the stratosphere around our planet,
it absorbs ultraviolet radiation from the sun,
protecting our bodies from being blasted by cancer-causing rays. Chemical pollutants
produced by humans can deplete ozone, too. Again, you really want an ozone layer.
"Without an ozone layer, UV radiation would sterilize the Earth."
Thankfully, like the ozone damage caused by human pollution, volcanic ozone woes
don't last forever. The ozone-depleting effects of an eruption are temporary and
often abate within just a few years. However, there's no telling how long
ozone damage might last in the wake of an especially powerful supervolcano blast.