You probably already have a vague notion of stegosaurus and other dinosaurs running amuck
and being trampled by roaring, panicked T-Rexs while fiery asteroids rain down from the heavens
and burn them all to death.
Well, yes, some dinosaurs were killed by asteroids, but the mass extinction of the dinosaurs is
a little more complicated than that.
First, it’s thought that dinosaurs roamed the earth for about 200 million years.
It’s likely that many types of dinosaurs lived and died out long before extinction
ended them for good.
There are three consecutive geologic time periods within the Mesozoic Era during which
the dinosaurs lived; the Triassic, Jurassic, and Cretaceous Periods.
Different dinosaur species lived during each of these three periods.
The Jurassic period dinosaur the Stegosaurus already had been extinct for approximately
80 million years before the Cretaceous period dinosaur Tyrannosaurus came to be.
So no, Tyrannosaurus never trampled a Stegosaurus while running from asteroids.
At the end of the Cretaceous period there was a mass extinction where around 75% of
life on earth was suddenly wiped out.
This included everything from fish, to trees to T-rexs.
This event is called the Cretaceous–Tertiary or K–T extinction which occurred 66 million
years ago.
The extinction is apparent in the geological record; no dinosaur remains have been found
in rocks younger than 66 million years.
Try to wrap your mind around this crazy fact--the time period separating the existence of Stegosaurus
and Tyrannosaurus (80 million years) is greater than the time period separating Tyrannosaurus
and modern humanity or you (66 million years).
For many years, paleontologists thought the mass die-off was most likely caused by climate
change which disrupted the dinosaurs’s food supply.
In 1980, nuclear physicist Luis Alverez and his son geologist Walter Alvarez were conducting
research in Italy.
They discovered a layer of iridium-rich clay in the K–Pg boundary which marks the end
of the Cretaceous Period.
This layer has about 200 more times the amount of iridium in it compared to the strata formed
before and after.
This was significant because iridium is rare on earth, but much more common in space.
The Alvarezes hypothesised that the iridium was deposited because of an astronomical event
where a large meteor, comet or asteroid collided with the earth.
Furthermore, this enormous impact could have caused the extinction of the dinosaurs.
In 1991, a massive meteor crater was discovered on the edge of the Yucatán Peninsula, extending
into the Gulf of Mexico.
The Chicxulub Crater, which was named for a nearby village, is 112 miles in diameter
(180 km).
For many in the scientific community, this crater confirms the Alvarez hypothesis--it
has become the widely accepted theory for the extinction of non avian dinosaurs.
Researchers believe that around 66 million years ago, an enormous asteroid somewhere
between 6-9 miles in diameter (9.6-14.5 km) struck the earth at 40,000 miles per hour
(64,373 kph).
The impact released 2 million times more energy than the biggest nuclear bomb.
But even with such a massive impact, how could that kill the majority of life on earth, including
dinosaurs thousands of miles from the impact zone?
As the massive asteroid streaked across the sky, chucks may have broken off, igniting
wildfires wherever they landed.
When the asteroid slammed into the Yucatan peninsula, it bore several miles down into
the seafloor creating a bubbling cauldron of melting rock and super hot gases.
This created an effect similar to a volcanic plume-heated seawater and lava were ejected
mountain-high into the atmosphere.
The plume quickly collapsed back into the sea where it cooled, altering temperature,
currents and the land formation.
The asteroid also vaporized sulfur rich rocks, releasing an estimated 357 billion tons (325
billion metric tons) of sulfur gas into the air.
Some of the gas quickly fell as acid rain, acidifying the ocean and killing off most
marine life.
At the same time virtually all life within around 1,000 miles (1,609 km) of the impact
was incinerated due to the heat.
The impact also created a shock wave and displaced ocean water, forming a towering tsunami that
might have traveled as far inland as present-day Illinois before receding.
The particles of dust and gases tossed into the atmosphere blocked the sun, plunging the
earth into darkness and cold temperatures.
The lack of sunlight reaching plants caused a massive collapse of the ecosystem throughout
the whole food chain.
The majority of plants and trees rapidly died off.
Shortly thereafter, herbivores starved to death because they had nothing to eat.
The carnivorous dinosaurs lasted a little longer, since they could feast on the dead
and dying herbivores.
But within a month or so of the asteroid impact, most of the life on earth had died.
Only small, scavenging animals that were quickly able to adapt survived.
These animals, which most likely subsisted on insects and seeds, burrowed into the ground
to escape the cold.
Over time these creatures evolved into modern reptiles and birds.
So technically dinosaurs never fully went extinct, they just became canaries and chickens.
Could an astronomical event destroy life as we know it on earth?
Check out our answer here:
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