"Scientists are releasing a new warning about the threat of a massive supervolcano eruption,
like the one under Yellowstone National Park."
"But it could be the world's most powerful natural weapon mass destruction,
if it erupts, scientists say it will be more powerful than 60 million atom bombs."
"It could destroy the United States as we know it."
There has been a lot of frenzied fear over an imminent apocalypse coming from the eruption
of the Yellowstone supervolcano.
And according to who you read, it could lead to anything from a mass drop in global temperatures
to the extinction of life on Earth.
But exactly how likely is this to happen?
An ordinary volcanic eruption would reach about 100 cubic kilometers of erupted magma.
Supervolcanoes can reach up to 5000 cubic kilometers in a single eruption.
Whereas a normal volcano builds up in a series of small eruptions producing a volcanic cone,
when a supervolcano erupts it generates a cavity in the ground as all the magma that’s
accumulated below the surface is expelled, that cavity is what’s referred to as
a caldera, a broad basin up to several tens of kms across. Although we do occasionally
see single calderas sitting on their own It’s much more common to see, what are known as,
caldera fields, which is groups of 5, 10, 20 or even more, calderas overlapping each other,
in a very wide area that might be hundreds or even a thousand km across.
Throughout history there have been over 100 super-eruptions.
But due to millions of years of erosion, it’s impossible for us to know when exactly they
happened and how many there have been.
Yellowstone is undoubtedly the most famous supervolcano caldera field in the world.
It is not the biggest - but due to its location, it could potentially cause the most economic
disruption to western civilization.
It’s produced three very large caldera forming eruptions in the last two million years,
it has also produced a very large number of smaller eruptions, at the moment, magma does seem
to be accumulating beneath it again, but there aren’t strong indications of very
large bodies of magma, so it may well be a quite long time yet,
before Yellowstone is capable of producing a supervolcano eruption again.
There’s another argument that says “okay it’s had three of these eruptions in the
last 2 million years, and the last one was about two thirds of a million years ago,
therefore we’re due for another one.
But that’s quite a naive argument,
in that it assumes the spacing between supervolcano eruptions
within a single volcanic field is uniform and when we look at other supervolcano fields,
that’s not the case.
If an eruption were to take place today, experts estimate a blanket of ash would cover most of the U.S.
It could also force vast quantities of gas, like sulfur dioxide, into our atmosphere.
Immediate impact of a supervolcano eruption can be divided into three parts.
Firstly, close to the caldera and extending for 100 km or more from the caldera,
there's a zone of complete devastation, outside that, there’s a zone of regional damage where
there is fallout of the ash that’s gone up into the atmosphere, and spread out in
a giant ash cloud. In the modern day context, the obvious consequence - suppression
of agriculture, disruption to transport, collapse of buildings with the ash accumulating on the roofs.
The third component is the very fine ash and the volcanic gases, spread out high
in the atmosphere, and spread out all over the world.
It’s been proposed that the amount of that ash, the amount of gas, which condenses to
form aerosols, is so great that, what it will do, is it will reflect back sunlight and the earth
will experience a period of global cooling.
The evidence from past supervolcano eruptions says that actually it may not be as bad as that.
"Now doctor, is this realistic? Or are we just scaring people out there?
Because people are writing in they're thinking we're talking about armageddon here."
So perhaps it’s not as apocalyptic as some may suggest.
Without the full knowledge of what’s happened in our past, it’s quite difficult to tell
what’s going to happen in our future.
Human society is both much more vulnerable to disruption from large scale natural disasters
like super-eruptions but equally we have much greater capacity to respond to it.
If we can foresee a super-eruption happening years or even decades ahead from that precursory
activity and we actually have the will to act upon that knowledge then we might be able
to cope an awful lot better than the hollywood movie view of a super-eruption might suggest.