HDTV Discovery 100 Greatest Discoveries 5of9 Evolution

A killer asteroid streaking

towards earth at 67,000 miles an hour

[explosion and drums]

Giant chimney like towers scorching hot

rising from the bottom of the ocean floor

[ music ]

a young man epic sea voyage that shook
the foundation of the world.

[explosions and Music]

An expedition back through time into
the heart of human ancestry

Of all the discoveries in the history
of science

Few have the power to compel...

Or the potential for controversy,

Than those concerning how life on earth
began

How species evolved

Why some species survied

And others become extinct

[rumbling and panicked roars]

These are the greatest discoveries
in the origin in evolution of life

[music climaxes]

[Theme Music of piano and violin]

[Bill Nye}
Life is a game of chance

The odds of surviving or facing extinction
are always changing

Now some changes are gradual;
the result of a slow process of nature

Others, happen in a blink

Like the one that caused the extinction
of the ancient Dinosaurs

[Music]

In 1980, a Geologist named Walter Alvarez

was studying rock strata in mountains
North of Rome

When he came across something curious.

a thin ancient layer of clay

(Scientist) So this clay layer here

marks the boundary between two

different geological periods. [music]

(Bill Nye) The layer of clay marked what is

known in geology as the KT boundary.

A dramatic turning point in the history

of the earth about 65 million years ago.

When the ancient dinosaurs mysteriously vanished.

For Alverez, here was the moment of discovery.

analyzing samples from the KT boundary

he found the clay contained

extremely high levels of aridium.

an element rarer on earth but abundant in space.

When similar levels of aridium where found

around the world Alverez began

wonder what could have caused it to blanket the

earth.

The answer he concluded was the impact from an asteroid
of gigantic proportions

Over six miles across

Taller than Mount Everest

Moving at a speed of 67,000
Miles an hour

[Boom]

Doctor Elisabetta Pierazzo is a research scientist
at the Planetary Science Institute

In Tuson Arizona

(Bill Nye)
So how much energy did this thing have?

[Elisabetta]
an energy that is about a
hundred million megatons

of TNT

This is about 10 times the worldwide

nuclear arsenal at the peak of the Cold War

[Bill Nye]
Ten times the worlds Nuclear Arsenal

when it was really big

[Elisabetta]
yes

[Bill Nye]
All in one place?

[Elisabetta]
all in one point released in...

a second. So that was a humongous amount of
energy

That was delivered to the Earth

[dramatic music plays]

[Bill Nye]
The devastation was colossal

[Dinosaur screeches]

A cloud of vaporized rock and debris
mushroomed into the air

blocking the Sun

scorching fireballs blasted across the face
of the Earth

The air became chocked with poisonous gas
and soot

nearly half of all life forms on earth

perished in the Apocalypse

including the ancient Dinosaurs

The only piece of the puzzle missing
from Alvereze's story was proof of the asteroid

if it was as big as he said it was

then it must have left quite a crater

finally Geologist found one that just happened
to be sixty five million years old

the Chicsalu Crater

an immense hole

1,200 miles wide

buried under a thick layer of sediment
at the bottom of the Gulf of Mexico

off the coast of the Yucatan Peninsula

[Elisabetta]
yes so, the complexity increases
with the magnitude

of the impact event.

Because the Chicsalu crater is under water

this is a good place to get a sense of
what happened

when the asteroid hit.

this is meteor crater Arizona

50,000 years ago...

A meteorite about the size of a house

streaked out the sky and slammed into the Earth

it triggered an explosion greater than
twenty million tons of TNT

And created this.

A crater five hundred fifty feet deep

and three quarters of a mile across

room enough for twenty football fields

and more than 2 million spectators

[Bill Nye]
Impressive, isn't it?

But remember, the asteroid that caused the
"KT" Event

was the size of Mount Everest

so to visualize the crater that it made
we need something a lot bigger

Like the Grand Canyon!

this is the South Rim.

from here to the other side is 16 Miles.

but even that's not big enough.

the Asteroid that caused the "KT" Extinction

blasted a Crater 8 times as large

one hundred twenty five miles across

from here to the gaming tables in Las Vegas

And when the Asteroid hit it went deep as well

It's a long climb from here to the bottom of the Canyon

about a mile and a quarter.

but according to Walter Alveraz, the Asteroid made a crater
that was a staggering 20 miles deep upon impact

then quickly filled in.

How do Scientist know all this?

the Evidence has come from a variety of sources

Seismec studies revealed the enormous ring like shape
of the Crater

Thousands of core samples uncovered rocks

with traces of having been altered by an high-impact
collision

And computer modeling that calculated the explosion
it would have taken to create

the Chicsalu Crater.

But Walter Alvarez's discovery of what caused
the extinction of the ancient Dinosaurs

is not without contraversy

his Asteroid scenario is at the center of an ongoing debate.

with opposing Scientist offering their own theories.

One theory argues that intense volcanic eruptions
poisoned the Earth's atmosphere

and killed the ancient Dinosaurs before
the "KT" Event ever occurred.