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this happened about 66 million years ago
the impact was as powerful as 10 billion
atomic bombs from the catastrophic
global effects on the environment were
even deadlier 75 percent of life on
Earth win extinct including a dominant
group of animals that has come to
mesmerize our attention the diversity
that we see dinosaurs is really a
reflection of how successful they were
meet Nat Geo Explorer Diego pol one of
the paleontologist who discovered the
largest dinosaur ever dinosaurs were
predominant in our world for over 140
million years humans have been in this
planet for two hundred thousand years
and there are not many cases in the
history of our planet that one group is
so predominant and so successful for
such a long time humans and dinosaurs
didn't overlap not even close and as
we've seen in Hollywood we can be
thankful for that but dinosaur fossils
left humans wondering where they go
dinosaur extinction has been a
fascinating topic for a long long time
we see their presence up to 66 million
years old and then after that there's
nothing they're gone
throughout the 20th century there were a
lot of arguments theories very
dramatically from the somewhat plausible
to the downright bizarre some pointed
out of control hormones or cataracts
others blamed a world taken over by
hungry caterpillars the answers eluded
experts until natal 18 when two
scientists working here discovered a
clue the link to it being an asteroid
impact started almost by accident and
Walter Alvarez and his father Louis
Alvarez were actually very interested in
a place called Rubio Italy
there were lime stones that were
rotational I'm stones that were after
the Cretaceous what we call the paleo
gene and that the extinction event was
right at that boundary instead of
finding anything sort of background
normal they actually found a spike in
something called iridium iridium is a
surprise because we have very little
iridium present on the surface of the
earth versus what the asteroids are made
of Walter and Louie
Alvarez co-authored a groundbreaking
paper hypothesizing that an asteroid was
responsible for the mass extinction but
that in itself raised another question
where's the crater scientists dug
further into the layer of iridium for
answers the real P clue was while it's
only a centimeter thick layer in most of
the world as you approach the Gulf of
Mexico that layer becomes much much
thicker they start seeing layers that
are a metre thick or even hundreds of
meters in places as you get closer and
closer to the place where the impact
happen by the early 90s the science was
becoming more convincing
more than three thousand feet below the
surface of the Yucatan Peninsula laid a
saucer-shaped structure different from
volcanic terrain
this was the Chicxulub crater so to
answer the fundamental questions about
how this particular impact caused a mass
extinction event we needed to drill into
it where it actually hit was lime stones
so calcium carbonate which makes a lot
of co2 when your paper eyes it but even
more important perhaps worth evaporites
these are rocks that are high in sulfur
and so when those get vaporized they
actually put native sulfur into the
atmosphere which when combined with
water becomes sulfate aerosols which is
a pollutant that actually succeeds in
cooling the planet off if it had
happened a little bit earlier or a
little bit later in terms of the
rotation of the earth it could have
easily hit the Atlantic Ocean or the
Pacific Ocean and entirely missed this
shelf environment with all these
sediments beneath it and if it had done
that most of the material that would
have been ejected would be the vaporized
asteroid and just water where it hit and
with the energy it hit seemed to have
had the right recipe to create a global
catastrophe dinosaurs were likely living
in a vulnerable time leading up to the
asteroid but perhaps more surprising is
the realization that not all dinosaurs
went extinct so most people think that
dinosaurs are extinct but this is
completely false because you know if you
look out your window you're gonna see a
living dinosaur
[Applause]
as a vertebrate paleontologist my
speciality is understanding how birds
evolved from dinosaurs and then also how
the earliest birds evolved into what we
would consider a bird today you have
this huge diversity of dinosauria and
then you have one group that's called a
theropod ah
and everybody knows theropods it
includes famous members like
velociraptor or t-rex but one group of
theropods eventually gave way to birds
this resilient group of theropods is
represented today by over 10,000 living
species of birds modern birds is the
most diverse clade of vertebrates living
on land on the planet today so people
are always saying that like this is the
age of the mammals I always like to joke
and be like it's still the age of the
dinosaurs
while the dinosaur extinction mystery
has come a long way since the early
theories discoveries today are still
necessary pieces of the bigger picture
you have to like puzzles and discovery
it's certainly important but it will not
answer all your questions it will be a
big and important piece to your puzzle
mass extinction events are incredibly
powerful tools for us to understand the
way life and ecosystem is operate and so
the Chicxulub event is the most recent
of these mass extinction events on earth
science is never done right we just find
more questions that need answering
you
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