It was the moment that reshaped our planet.
One fateful day 66 million years ago, an asteroid the size of a city came burning through the
skies at 40 times the speed of sound before crashing into the Yucatan peninsula.
There, it exploded with the force of seven billion Hiroshima bombs, liquifying the rock
below it, and blasting a crater some 180km wide.
The sound of the impact was heard around the world.
In the minutes after, plumes of rock enveloped the Earth in suffocating dust.
Wildfires broke out across multiple continents.
When the dust finally settled, it was onto a planet that had lost 75 percent of its lifeforms.
Today, the remnants of this long ago impact are all but invisible, buried beneath thousands
of meters of limestone.
Yet, the crater still remains, half hidden beneath the rainforests of the Yucatan, radiating
out from the small town that gives it its name: Chicxulub.
But what stories lie behind the Chicxulub crater?
What would it have felt like to be living on Earth at the moment the world ended?
Today, Geographics is winding the clock back tens of millions of years to witness one of
the most important days in history: the day the dinosaurs died.
The Lost World If you were to travel to the Yucatan rainforest
today and stand within the confines of the Chicxulub crater, you’d see a world that
hasn’t changed for centuries.
But no matter how deep you ventured into that rainforest, no matter how far you got from
human contact, you’d never find a world as pristine as the one that existed here in
the last days of the dinosaurs.
At the time of the Chicxulub impact, the planet was in the Late Cretaceous period.
Following on from its more-famous sibling the Jurassic, the Cretaceous was basically
the Jim Belushi of geological eras - far-less beloved, but far-longer lasting than its older
brother.
And we mean long.
When the Cretaceous began 145 million years ago, the supercontinent of Pangea was still
just about holding together.
By the time it ended in an apocalyptic blast nearly 80 million years later, Pangea had
broken up into landmasses pretty close to what we have today.
The wildlife had changed, too.
To return to one of our favorite ways of measuring time: you today are closer in time to the
last T-Rex than that T-Rex was to the Jurassic era’s stegosauruses.
But were you to jump in a time machine and travel back to the days of that last T-Rex,
what would you see?
Y’know, aside from the inside of a T-Rex’s stomach?
Well, the first thing you might notice is how hot this lost world was.
At the 45th parallel - roughly where the US-Canada border is today - the climate would’ve been
subtropical.
Even the poles wouldn’t have been cool enough to sustain year-round ice.
The second thing you might’ve noticed was how different it all seemed.
At the end of the Cretaceous, early forms of grass were only just starting to appear.
Most modern trees were non existent.
Ferns covered the land - not that there was much land for them to cover: the sea levels
were about 200m higher than they are today.
The result?
A planet that was only 18% land, compared to 28% today.
Even inland, vast shallow seas dominated huge swathes of the world.
But you probably wouldn’t be paying much attention to any of this.
Because the third thing you’d notice would be all the seriously huge dinosaurs!
In the southern hemisphere, sauropods like the Dreadnoughtus roamed the plains.
Clocking in at 26m long and weighing 60 tons it was the largest land animal to have ever
lived, a creature that would’ve made elephants look like mice.
In the sky above, Quetzalcoatlus soared - a pterosaur that stood taller than a giraffe,
and had an incredible 13m wingspan.
Then there were the smaller, but still pretty damn-big creatures.
Across the northern hemisphere, vast herds of Triceratops feasted on ground plants.
T-Rex scavenged alongside them.
In short, it was an incredible world, one we can only imagine.
And yet… in some ways, this lost world would’ve been very familiar.
By this point in history, flowering plants had finally appeared.
On the planet’s many warm shores, frogs, turtles, and crocodiles all lived; while modern
sharks swam in the oceans, passing over coral reefs.
Most-familiar of all, though, would’ve been the mammals.
While still small, these guys were now numerous enough to leap right in to any handy gaps
an asteroid impact might leave at the top of the foodchain.
In short, the Late Cretaceous was a boom time for ecology, with a wonderful, dizzying array
of creatures rubbing shoulders.
But, as we all know, this Eden was doomed.
Dinosaurs may have been around for 170 million years - a period of time so long that there’s
no point even trying to comprehend it - but their end was already approaching at supersonic
speeds.
For better or for worse, this world’s time was nearly up.
The Day of Armageddon In the course of Earth’s history, there
have been five - or possibly six - major extinction events.
But none were so literally explosive as the one that wiped out the dinosaurs.
The day of impact likely dawned just like any other day.
There were no portents.
No warnings.
Just the sun rising as it had every day for millions of years.
Well, we assume so, anyway.
Obviously with an event this far back, we have no way of knowing if the asteroid hit
in the morning, the afternoon, or the dead of night.
In fact, we don’t know a lot about this day in general.
This video is just using the most likely theories based on current research.
But adding endless caveats to our narrative would get super boring, so let’s all just
agree to allow us some poetic license.
When the doomsday clock finally hit zero on the Cretaceous era, it would’ve been shockingly
sudden.
You’ve probably seen footage of the Chelyabinsk meteor that exploded over Russia in 2013,
turning the sky a brilliant white.
Against the Chicxulub asteroid, that blast would’ve seemed like a firecracker against
a hydrogen bomb.
While the Chelyabinsk meteor was 18m across, the one that hit Chicxulub was nearly 10km
wide.
When it smashed into the Yucatan at 40 times the speed of sound, it was like hitting the
Earth with a planet-scale bullet.
In 1961, the Soviet Union tested the biggest bomb ever deployed: the Tsar Bomba.
It was the equivalent of setting off 3,800 Hiroshima’s simultaneously.
Chicxulub was like 2 million of those Tsar Bombas detonating all at once.
The ground in the Yucatan was vaporized in a split second.
Rocks from far below the crust were hurled high into the air - so high that a vast plume
of dust was raised into the atmosphere.
In the following seconds, an air blast shot across Mexico and Central America, flattening
forests for thousands of kilometers.
Up to 1,400km away the heat pulse sent temperatures soaring, igniting anything that could burn.
Scientists who’ve studied the impact claim the whole of modern Mexico was more-or-less
instantly reduced to a sea of flames.
If this was happening today, hundreds of millions of people would already be dead.
And things were about to get even worse.
As the forests burned, gigantic tsunamis swept across the Gulf of Mexico - up to 300m high
- tearing up the seafloor and annihilating coastlines.
Magnitude 10 earthquakes tore the Americas to pieces.
As far south as Argentina, the shock of the impact triggered landslides and volcanic eruptions.
It’s almost inconceivable that anything in the immediate area survived this Biblical-style
apocalypse.
But, if it did, it wouldn’t survive what came next.
Remember all those rocks from below the crust that the impact launched into the air?
Well, gravity was finally doing its thing.
As the earth shook, the landscape burned, and the tsunamis swirled, chunks of rock the
size of skyscrapers fell back to Earth, burying everything within several hundred km of the
blast beneath flaming rubble.
By this point, maybe a dozen minutes had passed since the asteroid came streaking out of the
sky.
Before three quarters of an hour had passed, things would go from “horrifying” to “literally
the end of the world.”
Armageddon From space, the Chicxulub impact would’ve
looked like a gigantic, angry flash, followed by a period of eerie calm.
As the minutes ticked by, that eerie calm would’ve been displaced by the sight of
a cloud of vaporized rock slowly pouring into the atmosphere, embracing the world in dark
fog.
Inside that fog, tiny particles called spherules were forming, made from the molten rock and
glass created by the catastrophe.
Only a few millimeters across, these spherules would’ve looked harmless.
Even strangely beautiful.
But that would’ve been only a fleeting impression.
After 40 minutes had passed, the spherules now surrounded the planet.
It was at this point that they began to fall back to Earth.
As University of Colorado geologist Doug Robertson explained to Smithsonian:
“The kinetic energy carried by these spherules is colossal, about 20 million megatons total
or about the energy of a one megaton hydrogen bomb at six kilometer intervals around the
planet.”
When the spherules fell, they superheated the atmosphere.
In some places, the upper atmosphere would’ve become so hot that the ground below burst
into flames.
The end result would’ve been uncontrollable wildfires breaking out across the globe, as
the spherules burned in the sky like falling stars.
For several hours intense heat swept the planet’s surface, turning lakes to steam, cooking alive
any animal unlucky enough to be out on the plain.
The only survivors in most places would’ve been those that were underground or underwater.
But even then it would’ve been dicey.
Even as the heat roasted the Earth, tsunamis were still sweeping the globe, swamping burning
forests and dragging the burnt carcasses of trees back out into the sea.
After the spherules finally stopped falling, the soot from the millions of fires would’ve
combined with the dust thrown up by impact, rising into the atmosphere and completely
shrouding the world.
Speaking of that dust; it’s extremely unfortunate that the asteroid hit where it did.
There have been over five bigger impacts than Chicxulub in Earth’s history.
One of them even landed after dinosaurs had evolved, and didn’t cause anything like
a mass extinction event.
But that’s what makes Chicxulub special.
It hit the Yucatan, an area with layers of many volatile rocks.
As National Geographic once put it: “There are relatively rare areas of the planet that
you can drop a 12-kilometer asteroid on and get the same level of atmospheric change.”
Chicxulub just happened to be one of them.
As the first survivors of the cataclysm began emerging from whatever rocks they were hiding
under, it was into a world that had changed beyond all recognition.
The land was now gray, coated with a thick layer of ash.
Forests were gone, coastlines devastated.
High above, soot and dust would’ve swirled across the skies, reducing the sun to a feeble,
almost invisible point.
These surviving animals couldn’t possibly have known it, but the devastation unleashed
by Chicxulub had barely even begun.
Had they been capable of abstract thought, they would’ve soon realized that the dead
creatures around them were the lucky ones.
Aftermath For
the next year, the Earth was plunged into an endless winter.
With the upper atmosphere so clogged, zero sunlight would’ve peeked through.
It would’ve been cold, dark, and nasty; like an ancient vision of the underworld.
It would’ve also been exceptionally deadly.
So, you might remember from biology class what happens to plankton when it goes without
sunlight.
To paraphrase a famously-terrible movie line: the same thing that happens to everything
else.
It dies.
Horribly.
While that sucked for the plankton, it also sucked for everything that ate that plankton
to survive.
And everything that ate the things that ate that plankton to survive.
And everything that ate the things that ate the things that ate… well, you get the idea.
Across the ocean, the entire foodchain collapsed.
On land, every single day became a hyper Darwinian struggle for existence.
We recently did a Geographics on Stalin’s cannibal island of Nazinsky, where thousands
of political prisoners were dumped in the depths of winter without food or water and
forced to murder and eat one another in order to survive.
That horrific experience lasted only a couple of months.
For anything alive after Chicxulub, it would’ve been like being stuck on cannibal island for
decades.
Starvation would’ve been the default setting of every living thing.
Thirst, too.
Acid rain fell from the burnt skies, poisoning water supplies, turning former forests into
the surface of the Moon.
In the decades after Chicxulub, around 75% of all species vanished.
The lucky 25% of species that did pull through were likely pushed to the very brink of extinction.
It’s thought today that no land animal larger than a raccoon made it through Chicxulub’s
great filter.
The only reason small mammals fared so well is because they required less food, and bred
faster.
But even for mammals existence still became an unending nightmare struggle.
Yet, even in these dark times, life found a way.
At ground zero, it was long assumed that the 32km deep impact crater would’ve been completely
sterile, a place nothing could survive.
But today we know that even at Chicxulub itself, cyanobacteria began creeping back within a
couple of years, creating toxic algae blooms.
As the sunlight began to return, the charred forests were repopulated, too.
First by ferns, and then by mosses and, eventually, more complex plants.
As the dinosaurs and their doomed brethren died off, the mammals moved into the spaces
left in the environment.
And, slowly, they began to thrive.
By the time 30,000 years had passed life was stabilizing.
Although it would take hundreds of thousands of years for ecosystems to settle into their
new grooves, eventually they would.
In this brave new world at the dawning of the Cenozoic era, those lucky mammals that
had survived would go on to evolve.
At long, long last, their descendants would become humans.
Recovering the Past So that’s What happened, but what about
the How?
Not how did an asteroid strike the Earth - that’s pretty self-explanatory - but how did we discover
the Chicxulub impact?
I mean, it’s not like there were dinosaurs keeping diaries.
The answer to that is almost as fascinating as the impact itself - albeit “fascinating”
in a way that involves far less mass death.
It wasn’t until fairly recently that “what killed the dinosaurs” became a question
people thought worth answering.
Part of this is to do with the fact that “dinosaurs” as a concept have only existed since 1842.
That was the year that parttime genius and fulltime jerk Richard Owen realized all the
fossils guys like William Buckland had been digging up over the previous 20 years were
clearly related.
Owen is the guy who gave them the name “dinosaurs”.
But even as these terrible lizards gripped the 19th Century imagination, no-one gave
much thought as to why they were no longer around.
It wasn’t until the turn of the century that people looked at this by-now gigantic
pile of ancient bones and started to wonder “what happened?”
And according to olde timey folk, what had happened was utter insanity.
At the saner end of the scale, you have George Wieland’s 1925 hypothesis that the dinosaurs
got so super into eating eggs that they devoured all their own offspring.
At the total looney tunes end, you have the gloriously named Baron Franz Nopcsa von Felső-Szilvás
declaring that the dinosaurs were killed off by their lack of sex drive.
But while it’s fun to discuss these old theories, like the one that seriously claimed
a whole bunch of very hungry caterpillars ate all the vegetation thus making the dinos
starve, we need to skip ahead in time a little now, to the late 70s.
Because this is when the existence of Chicxulub itself finally became clear.
In 1978, a geophysicist named Glen Penfield was working for Mexico’s state oil company
Pemex in the Yucatan.
As part of his duties, Penfield was flown out over the Gulf of Mexico with a magnetometer
so he could scan for oil.
Instead, he found something much stranger.
Below the waves, Penfield could distinctly trace the outlines of a perfect semicircle
- the underwater remains of the impact crater.
Unfortunately, Pemex refused him permission to make his findings public - beyond the fact
that there might be a big ol’ crater down there.
But soon others would independently begin looking for impact sites.
In 1980, Luis and Walter Alvarez discovered a thin layer in the geological record marking
the end of the Cretaceous across the entire world.
This layer was rich in iridium, an element rare on Earth, but common on asteroids.
That same year, the father son team declared their theory that an asteroid had wiped out
the dinosaurs.
It wouldn’t be long before others were backing up their findings.
There was Carlos Byars, the Texan journalist who was the first to link the Alvarez theory
with Penfield’s little-known crater.
There was Alan Hildebrand, who discovered evidence of an mega impact 66 million years
ago while working in Haiti, and summarized the Alvarez asteroid must’ve hit the Caribbean.
Then there was NASA scientist Adriana Ocampo, who discovered that the distribution of cenotes
in Yucatan - bright blue water holes the Maya once used in their rituals - formed the second
half of Penfield’s underwater crater.
In the early 1990s, all of the threads came together.
It was announced that not only was the Alvarez asteroid theory the best candidate for Earth’s
fifth mass extinction, but that the site was almost certainly centered on the town of Chicxulub
in Mexico’s Yucatan.
And, just like that, we finally discovered how the dinosaurs had died out.
Or did we?
The Endless Controversy Today, the Chicxulub theory is one of the
most-accepted in all of science.
Seriously, while researching this video, we saw people saying it was as sure a bet as
the theory of evolution.
But we’d be neglecting our duties if we didn’t point out that some super-qualified
people still believe that we’ve got it wrong, that an asteroid impact alone didn’t wipe
out the dinosaurs.
So what did?
Well, according to these guys, it was volcanoes.
Of the five mass extinction events in Earth’s history - six if you accept the argument that
the end-Guadalupian event should count - most of them are suspected to have been caused
by volcanoes.
In fact, volcanoes are the leading culprits in the Great Dying 252 million years ago,
the worst mass extinction event in Earth’s history, and one where up to 96 percent of
all species were wiped out.
Given supervolcanoes leading to climate change might’ve wiped out life on Earth on a pretty
regular basis, some started looking for evidence they killed the dinos, too.
In India, they may have found it.
The Western Ghats are a mountain range in the Indian south, formed when a huge series
of volcanoes known as the Deccan Traps blew their tops 66 million years ago.
We know that they started erupting 400,000 years before Chicxulub, and that overall they
sent 562,700 cubic km of material to the surface - tens of thousands of times what Krakatoa
unleashed.
But as to whether they killed anything more than a handful of unlucky dinos chilling out
in India, doing some yoga and finding themselves… well, that depends on who you ask.
Supporters of the volcano theory contend that the Deccan Traps had already unleashed so
much greenhouse gas into the atmosphere when Chicxulub hit that the Earth was already on
life-support.
So getting pummeled by an mega-asteroid was just the final blow in two-punch extinction
event.
This is backed up by a recent study showing a huge uptick in the amount of material the
Deccan Traps were sending out in the 100,000 years before Chicxulub.
On the other hand, supporters of the asteroid theory counter that a separate study published
the same year concluded that the Deccan Traps only became properly active after Chicxulub;
making them an apocalypse sideshow at best.
Weirdly, these arguments get quite heated.
Like, as hot as a spherule falling back to Earth.
Leading proponent of the volcano theory Gerta Keller has claimed that “impacters” have
tried to destroy her career and have her driven out of academia for being anti-asteroid.
And you thought your workplace was tough.
Still, for now, the Chicxulub impact remains our best guess for what happened to the dinosaurs.
Maybe it’ll be proven wrong in a few years.
Or maybe all this talk of volcanoes is just a load of hot air.
Today, the Chicxulub crater is all but invisible to the human eye - buried under tropical rainforests,
or simply lost beneath the waves.
If you were to travel to the town the crater is named after, you’d find nothing there
to tell you that this is it.
That here is the spot where the age of dinosaurs ended, and the age of mammals began.
Nothing to tell you that, without this one event on a single peninsula so many millions
of years ago, the dinosaurs might never have vanished.
Yet, sign or no sign, the impact of this invisible crater cannot be overstated.
In the months that Geographics has been running, we’ve covered all sorts of locations, each
important in their own way.
Some have been important to a certain region or certain time.
Some have been important to entire eras.
But none have been so important as the Chicxulub crater.
Without that long ago asteroid impact, none of those other videos would’ve had anything
to cover.
The Pyramids, the lost Mayan cities, the microstates, the prisons, the international borders…
none would’ve existed.
We’d have had no Mona Lisa, no Renaissance, no Bible, no Shakespeare, no agriculture.
There wouldn’t even be a we to know what we were missing.
There’d just be nothing.
Nothing but a watery blue world on which the human race had likely never evolved.
If just one of a billion variables had shifted even slightly, the Chicxulub impact could’ve
been in the open ocean, or somewhere where there was less volatile rock to choke the
atmosphere, or it could’ve missed Earth entirely.
Imagine that.
Imagine all the things that had to go horribly wrong for the dinosaurs to wipe them out that
fateful day.
All the things that had to go horribly right for us mammals to get a chance at ruling the
Earth.
If the history of all life on Earth is the history of a string of remarkable coincidences,
then this may be the most remarkable of them all.
Forget “the asteroid that killed the dinosaurs.”
We today should think of this vast, ancient crater as Chicxulub: the impact site that
made humanity possible.