Walking Through Time - First season

The Jurassic was not a theme park full of T-Rexes and velociraptors.

The reality is, that this was a waterworld...

...ruled by gigantic marine reptiles.

Much of what we know about these creatures of the Jurassic comes from

here, the coast of Devon and Dorset.

In just 95 miles,

the Jurassic Coast covers 200 million years of geological history.

It's a marvellous place.

The cliffs are packed full of fossils

from the tiniest of ammonites to giant marine predators,

unlike anything we have in the world today.

As a palaeontologist and evolutionary biologist,

I am fascinated by the unique geology of this coast,

that contains the most exquisite fossils.

Look at that!

And clues to what the distant past was really like.

These cliffs contain evidence

of ancient disasters that brought death to

the seas of deep time.

I'm going to walk this geological treasure trove and, along the way,

meet the people who have discovered the incredible creatures that are

preserved here...

Oh, look, it all fits together.

Is there anything else?

And reveal the evidence preserved in

these very cliffs of epic extinctions

that changed the face of this ancient world.

This is what we think is a deepwater death zone.

I'm here at the start of my walk on the Jurassic Coast.

Just look at those cliffs stretching out behind me westwards,

and all of them jam-packed full of fossils.

Now, Kimmeridge Bay behind me is no different.

The clays there in the cliffs are 150 million years old,

give or take a bit,

and they are full of preserved remains of ancient sea creatures.

To discover the story of the Jurassic Coast,

I will start my walk at the coastal village of Kimmeridge.

Then, via Lulworth Cove, head on to the pretty Osmington Mills.

After a visit to Dorchester,

I will rejoin my coastal walk at Abbotsbury,

just past Chesil Beach, and stop off at the seaside town of Lyme Regis.

Then, finish my trip at Budleigh Salterton,

just across the border in Devon.

Here, over 250 million years ago,

there was evidence of the worst extinction

of living creatures which ever

struck the Earth,

when something happened to turn our planet into a death zone.

A lot of the time, I'll be sticking to the clifftop paths.

The tides can catch you out on the beaches,

so you always have to know when high tide is to avoid getting wet.

Captured here at Kimmeridge is

a snapshot of an ancient world where Britain

was quite different.

In those days, 150 million years ago,

Britain was at the latitude of the Mediterranean Sea.

Sea levels were much higher.

And what is now Dorset was underwater,

beneath the waves of a shallow,

balmy Jurassic sea.

It was warm, tropical waters

and creatures living in those seas,

from giant plesiosaurs and ichthyosaurs,

giant sturgeons, right the way up to tiny ammonites.

When those creatures died,

they would fall down and rest on the bottom of the sea.

It was there on the seabed

that something totally amazing would happen.

The Jurassic Coast is special.

Here, a walk on the beach is like stepping into a time machine.

As you walk westwards, you head back in time,

through the Jurassic with its mega-beasts,

then 100 million years further back,

through the extinctions that changed the face

of the prehistoric world.

On these beaches, fossils are everywhere.

But how exactly where they formed?

It never ceases to amaze me

that a creature that lived hundreds of million years ago

can be incredibly beautiful and well preserved.

Of course, that is all down to fossilisation,

and that works in a rather wonderful way.

This is an ammonite collected locally.

You can imagine it swimming through

the seas maybe 180 million years ago,

and then it died, for whatever reason,

and plopped onto the sea floor.

And if it wasn't scavenged or broken up or decayed by bacteria,

it could lie there long enough

for sediment to fall down and cover it up

and it would become buried and a different process would set in.

Minerals from the surrounding sediments could penetrate

the ammonite's shell and replace it.

Effectively, the ammonite would become rock.

But a rock that captured the image of the way

the ammonite looked in life.

And there you have it, a fossil buried for millions of years, until

some keen fossil hunter might come along,

knock that rock open and discover it once more.

The seemingly endless supply of fossils turning up on the beach is

a by-product of a natural process, erosion.

When the action of weather and waves

causes the cliff face to disintegrate

and fall onto the beach.

Now, erosion is no joke.

Yes, it means fossils come crumbling out of the cliffs

so we can find them,

however, the same processes involved,

you can get clonked on the head by a falling rock, or in some situations,

whole sections of cliffs and houses on them can be lost to the sea.

Now, I'm standing on the foundations of Clavell Tower.

It was built in 1830, but it hasn't crumbled away.

Instead, it had to be moved from its perilous clifftop perch,

25 metres that way.

They say, it has bought it another 200 years.

Clavell Tower, a beautiful Georgian folly,

is now safe from tumbling over the edge of the cliff.

It's been restored by the Landmark Trust

and you can actually stay in it.

Here at Kimmeridge,

the geological layers are from the last days of the Jurassic,

around 150 million years ago.

A fossil falling out of a cliff onto the beach is lost forever,

without the eagle eyes of a dedicated fossilist.

So, how long have you been fossil hunting?

I've been fossil hunting since I was about six, so 20 years now.

That's a lot of time, a lot of fossils!

It is a few shedfulls. And a spare bedroom!

'Simon Penn turned his childhood obsession

'into a profession by becoming a palaeontologist.

'He is one of the most dedicated fossilists on the beach.'

How would you go about finding a fossil in Kimmeridge?

You're going to be out a lot,

walking long distances and looking at the floor.

I'm never sat splitting rocks -

that is a waste of time and a waste of energy.

I'm normally walking two or three miles before I spot anything

before I get a hammer or a chisel.

Basically, you're not enjoying the view?

No, no, no,

I've been all over the place. I've been fossil hunting in the sea,

snorkelling in America when dolphins came past and I missed them.

So, um... SHE LAUGHS

Honestly... Eyes on the prize!

Yes, yeah.

OK, so... Oh, look at these!

Grab a box each.

'Simon has brought some of his finest discoveries for me to see,

'and they are astonishing.'

These are all about 155, 154 million years old.

We'll start with these, which are pterosaur bones.

These are our flying reptiles.

This is part of the wing. That's the upper arm bone, a humerus,

and this is the radius out of the front of our arm there.

And this bit?

Yeah, we even think they might have been sat like seagulls

on the surface of the water.

I love that idea of these pterosaurs bobbing on the surface of this

ancient ocean. What sort of wingspan might that be?

Anywhere between 2 and 3.5 metre wingspan.

Wow.

'Among Simon's collection is a fishy find

'that looks like it died last week.

'Not over 150 million years ago.'

This is a caturid.

He's completely compressed, the whole animal's here.

The preservation is spectacular

because you can actually see right down into the gills.

Oh, yeah, look at those.

'The sharp teeth of this extinct caturid

'reveal that this was a little predator,

'a bit like a Jurassic sea bass.'

What's brilliant with a specimen like this is it gives us a real

snapshot, not just in millions of years, but in days.

We are looking at a specific event.

So this animal, we know died in warm seas,

and if a fish dies in a warm sea, he will fill with gas pretty quick,

float to the surface and then the stomach

is going to rip to let that gas out.

We've got evidence of that along here.

You can see the stomach is completely ripped open,

so all the gas has ripped out of this fish's stomach.

When you get this almighty Jurassic stinky explosion probably.

Yes, yeah.

He's fallen down through the ocean and hit the seabed

and he's gone into a sludge where there's not much oxygen and that's

helped preserve him. It's pretty spectacular.

It's really spectacular.

What an amazing find.

'But how exactly did this creature, from so long ago,

'become so perfectly preserved from its skin,

'right down to some of its internal organs?'

To answer the question,

I have to look closer at the layer that it came from,

a dark type of rock that is especially common in these cliffs.

The black shale.

I'm hooking up with an authority on the Jurassic Coast and its fossils,

professor of geology Paul Wignall of Leeds University.

This is absolutely glorious.

It's lovely, isn't it? I really want to get down there and have a look.