At the bottom of the Atlantic Ocean lies a chain of volcanoes,
stretching almost the entire north-south length of the globe.
It’s called the Mid-Atlantic Ridge, and it’s part of the longest mountain range in the world.
And while the eruptions of these volcanoes don't usually trouble us, their birth was once
responsible for ripping a supercontinent apart and creating the Atlantic Ocean that we know today.
Because, it didn’t always exist.
In our time, the Atlantic Ocean covers a fifth of
the Earth’s surface and influences the climate of the entire planet.
But before the Atlantic, there was the supercontinent of Pangea.
Pangea formed when most of the land masses merged around 320
million years ago and lasted for nearly 150 million years.
During this time, plants and animals extended their ranges
across regions now separated by vast expanses of ocean.
But towards the end of its reign, something big started brewing
beneath the supercontinent’s surface.
Heat began to build up in the mantle beneath Pangea – a concentration of
heat that would go on to completely change the course of life on Earth.
By some measures it produced the largest volcanic eruption our planet has ever seen,
splitting the supercontinent in half and forming the Atlantic Ocean.
Oh, and it caused a global mass extinction in the process.
The first sign of trouble came in the Middle Triassic Period, 230 million years ago.
A rift in central Pangea began to form,
stretching and pulling the continent apart, forming faults in the crust.
This began to split what is now Africa and North America.
It started slowly at first,
growing over 30 million years until it stretched for 5000 kilometers.
And all that time, heat kept building up beneath the supercontinent.
Where the heat came from is still a bit of a mystery.
It could have been a plume of buoyant magma from the mantle below,
but the morphology and the chemistry of the rock left behind, doesn’t quite fit this explanation.
Or it could’ve been that convection cells formed
at the edges of Pangea and funneled heat inwards, concentrating it below the rift.
Or, like a chicken sitting on an egg, the thick supercontinent might
have essentially incubated the mantle beneath it.
Whatever the source, around 100 degrees Celsius of excess heat
built up in the mantle beneath the supercontinent.
And then, all of a sudden, magma from this area
burst through the faults 201 million years ago and overwhelmed the rift.
This eruption was the Central Atlantic Magmatic Province or CAMP for short.
It erupted in four major pulses over 600,000 years.
And each of these were extremely brief in geologic terms – only
a few hundred or thousand years long. But each would have been catastrophic.
In total, the CAMP spewed out enough lava to cover over 10 million square kilometers!
That’s roughly the size of Canada.
In terms of how much of the surface of the Earth was covered,
that’s the biggest eruption we know of. Ever.
Most of this lava erupted in smooth flows that creeped across the land,
similar to what we see in Hawaii today.
And it was made up of melted tectonic plates
that had subducted into the shallow mantle long before Pangea had formed.
The lava cooled into a fine-grained dark volcanic rock called basalt – and today
it can be found all around the edges of the Atlantic.
Scientists first started to figure this out in the 1970s,
when they noticed similarities between rock formations in Florida and Senegal.
And those rocks were approximately the same age as the Atlantic,
leading to the idea this eruption caused Pangea to break up and the ocean to open.
Since then, many more matching rock formations have also been found in South America and Europe.
And in the 1990s geologists brought all these
observations together and the CAMP theory was born.
These massive eruptions affected more than just the geology – a Canada-sized
outpouring of lava is going to have a pretty big impact on anything living at the time.
And scientists had long suspected that the CAMP
eruption had something to do with the End-Triassic Mass Extinction.
But for a long time, they couldn’t prove it.
Because, while both occurred right around 200 million years ago, it wasn’t until 2013 that
they were able to figure out the age of the CAMP rocks precisely enough to know for sure.
See, when the CAMP basalts cooled from magma, crystals of the mineral zircon formed.
These crystals tend to incorporate uranium atoms into their structure while pushing lead atoms out.
Over time, the isotope Uranium-238 decays into Lead-206. And this happens very slowly – it
takes about four and a half billion years for half the Uranium-238 to make this transition.
So by counting the lead and uranium atoms in a crystal, scientists can calculate how long
it has been since that zircon cooled, along with the rest of the CAMP rocks around it.
This revealed that the end-Triassic Extinction started just 100,000 years after the CAMP
magma began rising into the upper crust, making a connection between the two events almost certain.
Which is maybe not surprising, because the entire duration of the CAMP eruption
would’ve been a brutal roller coaster of conditions for life on Earth.
When all that magma emerged through the rift across Pangea,
it poured sulfur dioxide into the atmosphere.
In the lower part of the atmosphere, this reacted to form acid rain which soaked into soils on land.
Higher up in the stratosphere, sulfur aerosols formed. Along with volcanic ash,
these reflected sunlight and rapidly cooled the planet.
And the combination of acid rain and volcanic winter was only the start of trouble for life.
Carbon dioxide came directly from the volcanoes,
as well as from magma reacting with the sedimentary rocks it flowed through.
This doubled carbon dioxide in the atmosphere,
emitting roughly as much as humans will by the year 2100.
The effects of the CO2 took longer to be felt, but warmed the planet by more than 4 degrees Celsius.
A little bit of warming also could have triggered
a runaway feedback loop by thawing methane clathrates.
That’s ice under the seafloor that contains methane gas within it.
This would have released methane into the atmosphere,
which is an even more potent greenhouse gas than carbon dioxide.
With rising temperatures,
wildfires tore across the continents, causing chaos for life at the time.
And we can still see the remnants of these fires preserved as charcoal in sediments.
Now, the oceans did absorb some of the carbon dioxide from the atmosphere.
But this caused the oceans to acidify and coral reef ecosystems collapsed.
96% of coral genera went extinct.
And on top of the climate changes,
the volcanoes emitted some nasty stuff like halocarbons and mercury gas.
Halocarbons degraded the ozone layer and exposed life to more
ultraviolet radiation, causing mutations.
And mercury did the same thing more directly. Of all the elements,
it’s the one that most easily causes potent damage to DNA.
We can actually see the effects of both of these in fossilized fern spores from the time.
They had higher rates of mutation than before or after.
So the end-Triassic extinction was pretty bad.
Overall, almost half of marine genera went extinct.
All but one ammonite and up to a third of bivalves were impacted.
And an entire class of eel-like creatures called conodonts went extinct.
On land, the extinction was the final nail in the coffin for many reptiles and amphibians,
although some were already declining by the Late Triassic.
For example plagiosaurs, a family of armored flat-headed amphibians met their end,
as did phytosaurs, reptiles that looked deceptively like crocodiles,
despite not being their direct ancestors.
But on the other hand, there was one group of animals that
fared pretty well through the end of the Triassic: the dinosaurs.
Some of their traits helped them out, like insulating structures called protofeathers,
which helped warm them during the sudden freezing of the volcanic winters.
And the end-Triassic extinction cleared out much of their competition,
setting the stage for their rise and domination throughout the Jurassic and the Cretaceous.
So splitting Pangea caused a mass extinction that altered the course
of life on Earth, along with beginning the opening of the central Atlantic.
Forming the entire ocean was a long process, which continues to this day.
The CAMP eruption eventually became the Mid-Atlantic Ridge. New seafloor
forms at this ridge and slowly spreads outward.
Today, the Atlantic Ocean is still widening by a few centimeters every year.
And this ocean has completely changed how our planet works.
The Gulf Stream current makes Europe’s climate
much warmer than would be expected from its latitude.
And the North Atlantic is the only location in the Northern Hemisphere
where dense cold water sinks to the seafloor and helps power global ocean circulation.
But it won’t be around forever.
The birth of the Atlantic was the first part of a pattern called the Wilson Cycle,
which also predicts how oceans close.
Today, the Atlantic is in its seafloor spreading stage, the mid-life of an ocean.
But we might be just starting to see the transition to the next stage.
Some scientists think that off the coast of Spain and Portugal,
the oceanic plate is starting to subduct beneath Europe.
And while it will likely be a hundred million years or more before the ocean closes,
when it does, the cycle will end with the creation of the Earth’s next supercontinent.
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Be sure to check out our episode, “When Dinosaur Look-Alikes Ruled the Earth”
to learn more about those croc-like animals that flourished during the Triassic Period.
And we lava this month's Eontologists!
Jake Hart, Raphael Haase, Annie & Eric Higgins, John Davison Ng,
Melanie Lam Carnevale, Addie, Tony Dai, and Juan M.
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Like this one from: Dara
Can you name two fossils from the Ediacaran Period?
Hint: they've been featured in Eons episodes.
Put your guesses in the comments and stick around after the blooper for the answer.
And as always thanks for joining me in the Adam Lowe studio.
Subscribe at youtube.com/eons for ancient adventures.
These crystals tend to incorporate [Michelle's nails click together] Uranium atoms ito their
structure while pushing Lead atoms out.
[off-screen] There was an extra sound?
That was my nails! [laughs]
Yeah, it was just my nail SOS.
Ok...
Dickinsonia & Charnia.
Other acceptable answers are Spriggina, Edicaria, and Kimberella.
Definitely should have remembered Kimberella.
Let us know if you got it right!
What is Kimberella?
But Dickinsonia is from the Ediacaran?