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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