Sometimes, after an earthquake has passed, the ground will shake again in an aftershock.
Similarly, if a smaller earthquake precedes a bigger one, it’s called a foreshock. So,
between foreshocks, earthquakes, and aftershocks, it can sometimes be that one single disaster
unfolds in many parts. But, on top of this, there’s also another, separate phenomenon
wherein clusters of full earthquakes are set of one after another, after another.
And scientists recently (and unexpectedly) experienced this in one of our planet’s
most unique settings: Antarctica. This is Unveiled, and today we’re
exploring how an underwater volcano caused 85,000 earthquakes in Antarctica in four months.
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We know that Earthquakes are one of the most destructive forces of nature on this planet. But,
often, it’s not the event itself, the actual shaking of the ground, that’s so lethal. Rather,
it’s the effects that that shaking causes. Violent vibrations in the earth can uproot and
destroy the infrastructure on top of it, and we’ve unfortunately seen many a city reduced to rubble
following a quake. Many related deaths come, then, via falling debris raining down onto the ground.
Or else, death comes from the secondary disasters that follow earthquakes, such as mudslides or
tsunamis. And, while the really big ones thankfully don’t happen every day of the week,
earthquakes aren’t rare. In any given year, around 500,000 of them are detected on average,
according to US government statistics… although the spread isn’t even. Most of them (about
ninety percent) occur around the infamous Pacific Ocean region called the Ring of Fire, an area
reaching from far east Asia and Australasia to the west coast of North and South America. It perhaps
came as something of a shock to scientists, then, when they recorded 85,000 earthquakes over just
a few months in, of all places, Antarctica. Details of the “massive earthquake swarm” were
published in an April 2022 report, in the journal “Communications: Earth and Environment”. In August
2020, an international team of researchers at a station on King George Island, close to the
Antarctic coast, caught wind of the first quake. That event in itself was somewhat surprising,
but the Earth moves in mysterious ways (literally in this case) and the team might’ve reasonably
assumed it to be a one off. But then another one came, and then another… and, well, from that point
on the earthquakes just kept coming. On King George Island, an incredibly remote location,
the team were reportedly hard-pressed for the facilities needed to measure seismic activity,
but they managed to pool data from various sources that were picking these things up. And,
ultimately, they started measuring the Antarctic quakes in August (following the first one) and the
unprecedented shaking didn’t calm down until November of the same year. They recorded a
near continuous stream of earthquakes for around four months, and still more (at a reduced rate)
in the weeks that followed… and by the end, they really had measured around 85,000 in total. The
majority of them were minor, but there were some larger ones registered, too, including a 5.9
magnitude quake in early October and a 6.0 toward the end of the swarm, in November. For reference,
those quakes will have packed the energy equivalent of around ten thousand tons of
dynamite. And there were long term effects from some of the shaking, too, with it found that the
island on which the team was based had actually been displaced by around four inches. The ground
had literally been reshaped beneath their feet, if only by a small amount. All in, big or small,
the four-month run now stands as the longest and most powerful seismic activity in Antarctica in
recorded history. So the King George Island team (and many others from around the world) were left
with one simple question; how did it happen? Often, earthquakes are plainly the result of
tectonic plate activity. When two plates meet, deep in the earth, they rub against, pull away,
or push above and below each other… which generates a lot of pent-up energy. As Earth
is tectonically active, the plates are always on the move and sometimes, inevitably, they slip…
at which point that pent up energy is released, powerful waves rush through the ground, the ground
shakes, and an earthquake takes hold. It’s why so many earthquakes happen along the Ring of Fire,
because there are so many meeting points between tectonic plates there. But it’s thought that this
more typical process isn’t what caused the 85,000 earthquakes in Antarctica.
Here, while we are still dealing with a plate boundary - along the edge of the Antarctic Plate,
in a region known as the Bransfield Strait - it’s less about the plates pushing,
pulling, or rubbing against each other directly. What’s more important are the cracks and fissures
that have formed along the strait (over thousands of years) thanks to tectonic instability. So much
so that nowadays it’s a reasonably unknown realm of underwater volcanoes down there.
These mountainous, submarine features aren’t quite so world famous as some of their on-land
counterparts, but they’re no less powerful. The team on King George Island found that one
particular volcano – called the Orca Seamount – seemed to be the most likely cause of their
sudden rush of quake activity. This was strange from the outset, though,
as the Orca Seamount had previously been listed as inactive… meaning it hadn’t erupted recently
and was deemed unlikely to blow in the here-and-now. But logically it must have erupted,
or something must at least have happened to it, if 85,000 earthquakes were being traced back in its
direction. There followed an investigation into the magma flow beneath and around the volcano,
the movements and pressure of which it was found might theoretically have set the earthquakes
off – with the magma pressing through the Earth’s crust. The fact that the quakes
largely stopped in November poses another problem, though, as it would imply that
the pressure was released somehow… again, most likely, via eruption. So, it could be
that the Orca Seamount did erupt… but there’s no direct record of that event,
and so it’s challenging to prove that that’s what happened. Again, the limited technology
available to those on King George Island was reportedly a limiting factor for further study.
So, where do we go from here? We know that 85,000 earthquakes certainly took place; we’re
not exactly sure why they happened; but there’s a pretty good theory involving an underwater volcano
that had previously been believed to be out of action. One possible course of action would
be to send a probe beneath the waves to more closely examine the seafloor around the volcano,
to gain a better idea of any eruption event that might’ve taken place. However, at present,
there are no plans do so. Nevertheless, the study until this point has been widely celebrated
as successful example of what can be achieved even without masses of high-tech gadgetry. Again,
the team behind it were hindered throughout by a lack of facilities to measure seismic activity
and they were working in an extremely isolated environment… and yet they’ve still managed to
paint a picture for the wider world of what’s generally considered to be an incredible unusual
Antarctic event. A truly unique and special few months in the history of this icy world.
Clearly, there remain questions left to answer, like; what’s really happening beneath the Orca
Seamount? Should a sudden rush of earthquake activity really go down as though it’s an anomaly,
or should we now expect to see more events like this in the future? And just exactly
what is the Earth trying to tell us when it rumbles for so long at its southernmost point?
In the coming years and decades, research into Antarctica specifically is set to increase.
Of all the continents on Earth, it remains by far the least explored, the most hostile, and
the most mysterious. But that also means that we have so much left to learn from it. And, really,
the uncovering of endless tectonic events is just the latest chapter in the story.
Because that’s how an underwater volcano caused 85,000 earthquakes in Antarctica, in four months.
What do you think? Is there anything we missed? Let us know in the comments, check out these other
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