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,