Hi. Good morning.
I want to talk to you about the extinction of the dinosaurs today.
Dinosaurs lived a long time ago.
They died out about sixty-five million years before humans,
before we, arrived on the scene.
Dinosaurs were actually here for a very long time.
From the very beginning of the dinosaurs to their extinction
is about a hundred and eighty million years.
So, there is more distance between the more recent dinosaurs and the very early dinosaurs
than there is between the last dinosaurs and humans.
People don't usually think about that.
Anyway, the dinosaurs were around for about a hundred and eighty million years
and then, suddenly, they disappeared.
I mean, not overnight, but pretty quickly.
Now, this extinction is called the K-2 extinction.
K-2 stands for cretaceous-tertiary.
The cretaceous period was the very last period of the dinosaurs.
Now, no one actually knows why this happened.
We have some ideas, and there are three theories,
which I'm going to try and explain to you now.
The first theory is volcanoes.
Right now, on Earth, we have numerous supervolcanoes all over the place.
In fact, Yellowstone National Park in America is a supervolcano.
Were that to erupt, it would cause mayhem and havoc.
If you've seen the movie 2012, that features quite strongly in that movie.
Anyway, back when the dinosaurs
were around, we had things, well, even now,
we have things called Deccan traps.
Now, these Deccan traps are giant areas of volcanic lava and magma.
They are enormous. They are bigger
than even supervolcanoes.
Now, these giant traps release gasses into the atmosphere.
They release volcanic gasses, they release Sulphur dioxide.
And what that does is basically
it creates climate change.
In fact, when the dinosaurs were around the climate dropped ... the temperature dropped by about 2℃.
If you are a lizard, if you are a dinosaur,
if you rely on warm temperatures to survive,
a drop of temperature like that can be fatal.
And that did kill a lot of dinosaurs, however, it wasn't the main reason for the extinction.
The second theory is sea level drop.
Around about the time the dinosaurs disappeared, world sea levels suddenly fell.
You can see this if you look at cliff faces, if you cut into a mountain or if you look at a cliff,
you can very clearly see where the seabed
used to be.
And it's much much higher than it is now.
What caused that?
Probably, the mid-ocean ridges, the mountains in the middle of the ocean, collapsed.
That would have caused earthquakes and tsunamis, but it would also have meant that the sea level dropped.
Now, that did kill dinosaurs, but it probably only
killed dinosaurs that lived in coastal areas; dinosaurs that relied on the sea for their life.
Because the sea level drops it doesn't
disappear and dinosaurs can go to the new sea shore, the new coast.
So, again, it kills off a lot of dinosaurs, but it doesn't kill all of them.
The third theory, and probably
the most likely, is a meteor.
A meteor is a piece of rock, well a piece of ... pieces
of metal and rock and sand and dust and ice.
That have survived since the beginning of
the ... since the creation of the solar system.
They are what's left over from when the planets were formed. And these meteors, they fly all
around the solar system and occasionally,
they fly into the planets.
Earth has been hit by numerous meteors over the ... over the course of its history.
Now, the one meteor that people suspect was the cause of the dinosaur extinction landed in Mexico.
How do we know this?
How do the experts know this?
If you cut into the earth again, around the world there is a layer of iridium.
Iridium is a
type of metal that you do not find on Earth,
but you do find in meteors.
How did that layer of iridium become spread evenly around the Earth?
Well, the only possible solution is because a meteor hit the Earth, evaporated,
became dust and the dust settled all over
the planet.
Now, why is a meteor a candidate for the extinction of the dinosaurs?
Well, because, if you look at the iridium layer,
if you look at the K-T boundary, underneath it there are dinosaur fossils,
above it there are no fossils.
So, why would a meteor cause
the extinction of the dinosaurs?
Well, if you got a stone and threw it into some sand, or threw it into some water, what happens?
The sand and the water splash up. Now, if
you take that to a much larger scale, if you
throw a giant rock at a planet, what happens?
Well, the surface of the planet liquefies,
becomes dust, and that dust sprays up into
the atmosphere and forms a cover all over
the planet. And, what that does is, it shuts
out the sunlight. It causes a ... well, a
nuclear winter. In the beginning there is
heat, there's radiation, but, once that dies
away, the sunlight is gone. And back then
the sunlight was gone for a year.
Maybe even longer.
And with no sunlight temperatures
drop. The global temperature dropped by 7℃.
Plants die. Animals that rely on heat die.
It's extremely hard to live.
Plus, sulphuric acid is released into the atmosphere, which turns the rain to acid rain, which turns the
water to acid water. Dinosaurs could not survive this.
Mammals. Mammals could survive. Why?
Mammals can live underground. Mammals can
eat insects and plants. Mammals can eat dead things.
Mammals can regulate their own body
temperature. They can stay warm when it drops
... when it gets cold. They are very good
at surviving.
Now, the site in Mexico where the meteor hit, they think
... the scientists
think that the meteor was probably 15km across.
A 15km meteor hit the Earth and caused this much damage and
caused the extinction of a major species.
Could that happen again? Of course it could. Meteors have hit Earth all
through Earth's history. However, Earth is
very fortunate in its position.
Two things protect Earth from being hit by more meteors.
The first thing, if it's night and you look into the sky you can see this,
the first thing is the moon. The moon actually protects us,
it shield us ... it shields us. It receives
a large amount of the meteors
that would otherwise hit Earth.
And the second thing, you can also
sometimes see in the night sky, is Jupiter.
Jupiter is a gas giant. The most massive planet
in the solar system.
And Jupiter's gravity is so strong that most of the meteors in the solar system are attracted towards Jupiter.
And hit Jupiter. So, thanks to Jupiter and
thanks to the moon, hopefully, we won't be
hit by a meteor for a while. But, one day,
it will happen.
And what will happen to mankind?
Will we go extinct, too?
I've no idea. I hope
not.
Anyway, thanks for listening. Goodbye.
