{♫Intro♫}
The event that killed the dinosaurs might
be the most famous
mass extinction ever.
And scientists are pretty sure they’ve identified
the scene of the crime:
a meteor crater in the Gulf of Mexico.
But that event sixty-six million years ago
is neither the only one in Earth’s history,
nor the worst.
Not by a long shot.
Scientists studying a remote swath of land
in Russia have pieced together clues about
an extinction event
that makes the demise
of the dinosaurs look tame.
The extinction event in question happened
at the end of the Permian period, which was
a geologic span of time that ran from about
299 million to 252 million years ago.
This was before the dinosaurs, but not so
far back that life on Earth would have seemed
totally alien. There were no birds or mammals,
but there were reptiles, amphibians, ferns,
and insects.
Granted, some Permian creatures -- like Dimetrodon
look pretty strange to us now, but you’d
still be able to walk around and see plants
and animals you could put a name to.
But at the end of the Permian, a lot of life
suddenly went extinct. Like, a lot.
Within no more than two hundred thousand years,
most of the marine and terrestrial species
on Earth vanished.
Estimates vary, but more than 90% of all species
may have disappeared.
It would take about 8 to 9 million years for
Earth’s ecosystems to really recover. This
extinction was so dramatic
that scientists have nicknamed it
“The Great Dying”.
There have been a handful of hypotheses over
the years to explain this massive die-off.
Some researchers have proposed another big
asteroid, like the one that would kill off
the dinosaurs.
But one place on Earth seems to stand out
as the most likely scene of the crime: a massive
volcanic region in Russia known as
the Siberian Traps.
The rock underneath this area of Siberia is
relatively stable --
it’s not on a tectonic plate boundary,
like many volcanoes are.
But about the same time as the Great Dying,
a massive pulse of magma from deep inside
the Earth —
known as a mantle plume —
melted through the crust.
The plume triggered the biggest volcanic eruptions
ever known, which may have lasted more than
a million years,
and covered an area
bigger than Greenland in lava.
After the initial eruptions, there was a quiet
period for a while, followed by one big, final
burst of activity.
These eruptions happened at pretty much the
same time as the mass extinction, and scientists
think this volcanic activity is a pretty likely
explanation for what happened.
The eruptions could have spewed massive amounts
of carbon dioxide and methane into the Earth’s
atmosphere, changing the chemistry
of the Earth’s air and water.
The oceans, for instance, would have abruptly
become more acidic and as much as ten degrees
warmer --
and would have lost
almost all of their oxygen.
If that seems bad, you’re right!
But there’s still some details to work out.
Sure, we found a site of massive volcanic activity,
and it’s about the right age.
But the timeline actually isn’t quite right
for the initial burst of eruptions
at the Siberian Traps
to have caused the Great Dying.
By the time the extinction event started,
the traps had already been erupting
for about three hundred thousand years and
had spewed out
two-thirds of their magma.
Also, this kind of massive eruption has happened
in other times and in other places. Some of
those are associated with mass extinctions,
but not all.
So does that let the Siberian Traps
off the hook?
One leading hypothesis, published in 2009,
proposes that it was volcanic activity but,
remarkably, it might have not been those
huge initial eruptions.
Remember that quiet period? During that period,
magma was still flowing, but instead of erupting
dramatically, it spread underground, intruding
in between layers of existing rock to form
what are known as sills.
Visible today in places like river banks,
the sills look kind of like the frosting in
between the layers of a giant cake.
As the magma spread out, it heated and altered
the surrounding rocks in a process known as
contact metamorphism.
These existing rocks, put downs by millions
of years of geologic activity, contained quite
a bit of carbon, and even included coal beds.
The intruding magma would have effectively
“cooked” all these rocks, creating and
releasing greenhouse gases like
carbon dioxide and methane.
They would also have released a type of chemical
called halocarbons, which would have stripped
the ozone layer, just like CFCs in more recent years.
And researchers have calculated that the contact
metamorphism generated four to nine times
more carbon dioxide than the lava itself contained.
In 2017, researchers took a closer look
at the start of this quiet, deadly period.
And they were able to pin the timing down
to line up with the onset of the mass extinction,
thanks to very precise radiometric dating,
which uses the steady decay of radioactive
elements like a clock
to estimate the age of rocks and other materials.
This research would explain why it took
300,000 years for the extinction
to start. The big eruptions, though dramatic,
may not have brought up enough carbon dioxide
by themselves, nor did they cook as much of
the underground rock as the sills.
And all that carbon dioxide, once released
from the cooking rocks, would be enough to
change the Earth’s atmosphere,
leading to warmer temperatures
and acidic, de-oxygenated oceans.
And from there to the most staggering loss
of life our planet has ever seen.
This may be the best smoking-gun evidence
we ever get to tie the Great Dying to a place
on Earth that you could actually theoretically visit.
And it’s a bunch of volcanic rock
in Siberia.
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