[train whistle toots] - ♪ Dinosaur Train ♪ - ♪ Once upon a time, there was a mom ♪ ♪ Her name was Mrs. Pteranodon ♪ ♪ Sitting on her nest, she heard a scratching and said ♪ - Oh, boy, my eggs are hatching!

- ♪ One by one, her kids popped free ♪ ♪ Baby Pteranodons, one, two, three ♪ - I'll name you Tiny, Shiny, and Don.

- ♪ But Tiny said ♪ - Wait, there's one more, Mom!

- ♪ The last little baby was a different size ♪ ♪ With teeth and a tail and big green eyes ♪ ♪ He didn't look anything like the rest ♪ - What am I doing in a Pteranodon nest?

- ♪ But dear old Mrs. Pteranodon said ♪ - Oh, this is your family, and I'm your mom.

You may be different, but we're all creatures.

All dinosaurs have different features.

Come on, Buddy, we'll take a vacation.

I'll get us a ticket at Pteranodon Station.

We'll travel the world in sunshine and rain and meet all the species on the... - ♪ Dinosaur Train ♪ - ♪ Dinosaur Train ♪ - ♪ Dinosaur Train ♪ - ♪ Dinosaur Train ♪ - ♪ We're gonna ride... ♪ - ♪ Ride, ride, ride, ride ♪ [train whistle toots] - ♪ The Dinosaur Train ♪ - [roars] - Tickets.

Tickets, please.

all: Hello, Mr.

Conductor!

- Where's Mrs. Pteranodon today?

- Oh, she's taking a little time for herself.

A little Mom vacation.

- A Mom-cation.

- So it's just me and the kids.

- Excellent.

Anyone feeling excited about our special secret trip?

kids: Yes!

- Especially me, because you said it was secret and it involved digging.

- That's right.

I did.

- And you know what digging means?

Holes!

- And you know who loves holes?

- Me!

- Wait.

We're going on a trip to a hole?

- More than just a hole, Shiny-- a cavern.

- Hooray!

We're going into a cavern!

Wait.

What's a cavern?

- You know what caves are, right?

- Yes.

I love caves.

- Good, 'cause a cavern is a huge cave that goes on and on underground.

- Mm, I'm not sure I like this idea.

- Good morning, everyone.

kids: Gilbert!

- Gilbert?

Are you coming to the cavern too?

- Ab-so-tootly-lutely, Miss Shiny.

I wouldn't miss it.

- All right, then.

I like this idea.

[ting] - Can we show them where we're going, Uncle Conductor?

- Well, we could show it to 'em, but I'd rather sing it to 'em.

Oh, yeah.

- Whee!

- Whoo-hoo!

- ♪ We've been up ♪ ♪ We've been down ♪ ♪ Here and there, all around ♪ both: ♪ But this time the train's going underground ♪ - [gulps] - ♪ Deep down under the Earth's foundation ♪ ♪ There's a place called Cretaceous Cavern Station ♪ - ♪ But, my friends, that's just the start ♪ ♪ We're digging down to a deeper part ♪ ♪ We'll dig as deep as we can handle ♪ ♪ Maybe all the way till we reach the mantle ♪ - ♪ We'll probably stop there, it's pretty hot there ♪ all: ♪ What's at the center of the Earth?

♪ both: ♪ Who knows what we'll discover?

♪ all: ♪ What's at the center of the Earth?

♪ both: ♪ Who knows what we'll uncover?

♪ - ♪ Caverns ♪ - ♪ Rivers ♪ - ♪ Jewels and minerals ♪ - ♪ But I hope not red-hot lava ♪ all: ♪ What's at the center of the Earth?

♪ ♪ ♪ - ♪ I'm so glad we're on this ride ♪ ♪ Who knows what's on the Earth's inside?

♪ - ♪ Can we dig right through ♪ ♪ And come out the other side?

♪ - ♪ A fun thought, Don ♪ ♪ But probably not, Don ♪ - Aw.

all: ♪ What's at the center of the Earth?

♪ ♪ ♪ ♪ What's at the center of the Earth?

♪ [all cheering] - Mr.

The Conductor?

- Yes, Mr.

The Don?

- Is Cretaceous Cavern Station at the center of the Earth?

- Actually, it's way up here.

See, if you look at the layers inside the Earth, We all live on the thin, solid outermost layer, called the crust.

Even though it's miles and miles thick, everything we know, from our mountains to our oceans, lies way up on top of that layer of the Earth's crust.

- But we are going to dig a giant hole in the crust, further down, right?

Yes.

As far down as we can dig, before we reach this area, called the mantle.

It's very thick and very hot.

And beneath that layer is the core, which is extremely hot, nearly as hot as the surface of the sun.

all: Wow.

- We're not going there, right?

- Not at all.

We'll just be digging up here, in the crust, near the top-- no digging down into the core, not even the mantle.

- Just...the...crust.

- Just...the...crust, period.

- Whew.

- Yay!

I can't wait till we dig through the crust and then the mantle and then the core till we reach the center of the Earth.

What's that made of?

- Not rock or dirt.

I'm gonna have to come up with a good hypothesis.

- All we can do is hypothesize, Buddy.

We don't know what's at the center of the Earth.

It's so hot, we can't even get close to it.

- This is going to be the best hole ever.

[bell chiming] - Oh, my.

Time to go underground.

Ready, everyone?

all: Ready!

- Not so ready.

- 'Cause it's time for a Time Tunnel.

Time Tunnel approaching.

Next stop, Cretaceous Cavern Station.

Here we are, deep under the Earth.

Welcome to Cretaceous Cavern Station.

all: Whoa!

- All right, everyone, follow me to our most experimental train yet.

- Dinosaurs and Pterosaurs, may I present the latest invention from Dinosaur Train Industries, the Drill Train.

all: Whoa!

- It's huge!

- Today we'll ride along in comfort as the Drill Train drills a brand-new tunnel down into the Earth's crust, on a voyage of discovery.

- What are we going to discover?

- We're looking for right place to build a brand-new underground train station.

- But why are you building a station deeper underground?

- Yeah, no one lives farther down, right?

- You'd be surprised, Shiny.

A lot of creatures live farther underground than this.

They just get tinier and tinier the deeper down we go.

- Rawk!

Tiny?

All right!

- So we've decided to build a station that caters to our deeper-underground clientele.

- It is our goal to ultimately reach every corner of the Mesozoic.

- All aboard the Drill Train!

- Whoo-hoo!

Yeah!

- All right!

The Drill Train.

- We're actually going to drill down into the Earth in this thing?

- Yeah.

What are we waiting for?

Come on!

Rawk!

[whirring] all: Ooh!

- Hey, Shiny, how are you doing?

- [whimpers] - Just relax and enjoy the ride.

- Well, I'd feel a lot better if there was something outside the window besides rock.

- First stop-- we're here.

- We're here?

Where's here?

[rumbling] all: Ooh!

- Hooray!

Is this the center of the Earth?

- Well, Don, in fact, we've barely scratched the surface.

- We Troodons are gonna get out and have a look around.

See if this is a likely spot to build our underground station.

- Wow.

- Rawk!

It's pretty neat.

But why would this be a spot for a station?

It kind of just looks like a hole in the dirt.

- This is a great spot for a station.

Look, there are all kinds of interesting shapes in the rocks.

You can really see the different layers.

- Dad?

Can we go explore a little?

- All right, just stay within "rawking" distance!

- Okay!

Rawk!

- Rarr!

- Shiny, don't you want to explore and see if we can find any strange underground life?

- Don, I'm pretty sure that nothing could live this far down, no matter how strange.

all: Aah!

- Oh.

Oh, hello.

- Rawk!

Hello.

Sorry.

You just really surprised me.

- Oh, I surprised you?

How do you think I feel, digging around and running into a giant drill train and a bunch of surface creatures?

You are surface creatures, right?

- Right.

- I haven't spent much time on the surface, you know, above ground.

- So you have been above ground?

- Sure.

It's nice, I guess.

I live near the surface most of the time, but occasionally I like to go for a deep dive way down here.

I just love to dig.

- Hello.

I'm Tiny Pteranodon.

- Oh, I'm Natasha.

I'm a Necrolestes.

- We're Pteranodons.

And Buddy is-- - [gasps] He's a T. Rex, right?

I've heard of those, but never seen one.

- This is so great.

I've never seen a Necrolestes either.

Do you mind if we compare features?

It's kind of my thing.

- I would love it.

Let's start with you, Buddy.

- Okay.

T. Rexes have big hind legs, three-toed feet, lots of teeth, a great sense of smell, and great eyesight.

- Oh, great eyesight isn't really very important if you're always tunneling in the dark.

I can see, just not very well.

I've got a big snout, a short body, and wide legs.

They're all especially helpful for digging tunnels, and living underground.

- Wow!

So you're like an extra-amazing digger.

- Oh, thanks, but there are even better diggers than me down here.

- There are other creatures down here?

- Sure.

It's amazing underground.

I can show you around.

- Oh, that would be nice.

I'm...kind of nervous.

Underground is a little scary.

- Scary?

Nah.

Stick with me, Shiny.

I've lived my entire life underground, and nothing bad has happened to me yet.

- Thanks, Natasha.

I don't feel quite as scared now.

I think I can handle this... as long as we don't dig deeper.

- Well, of course we're gonna dig deeper.

- Oh.

- Come on, everyone, back to the Drill Train!

- Where are we going now, Mr.

Conductor?

- Well, although this could be a perfect spot for a station, I have a hunch that if we dig deeper, we'll find a more perfect spot.

- [gasps] This Drill Train of yours is the most amazing thing I've ever seen.

- Isn't it?

- Huh, digs pretty fast, does it?

- Amazingly fast.

- Well, you know, after this layer of dirt, you'll hit some solid rock.

I've never dug farther.

- The Drill Train will dig right through that solid rock, Natasha.

- Oh.

Wow!

- Natasha, would you like to join us in the Drill Train?

- Oh, Shiny, love to.

- All aboard!

Let's dig deeper!

all: Yes, let's dig deeper!

- Rawk!

Okay, since we're all the way down here, we might as well dig a little deeper.

all: Yay, Shiny!

Let's dig deeper!

♪ What's at the center of the Earth?

♪ - Hi, there, I'm Dr. Scott, the paleontologist, and we're here in the paleontology lab at the Natural History Museum of Los Angeles County.

Once fossils come out of the field, they come to places like this, where folks like Ishelle, who are volunteers, prepare the fossils.

And she's working on the skull of a Ichthyosaur, a prehistoric marine reptile that swam in the seas during the Triassic time period, 240 million years ago.

So this specimen was buried for 240 million years.

It was discovered by paleontologists, brought back to Los Angeles, and it will take months to maybe a year or more to prepare this skull so it can be studied.

And to prepare the fossils, that means they use a range of tools-- sometimes air abrasives, sometimes tools that you might recognize, a toothbrush, for example... or a dental pick, which you might have seen at the dentist's office.

And it's with this range of tools that Ishelle is removing the rock, revealing the fossil, and once it's fully revealed, it is given a specimen number, a card is written up about it, and then it is time to transport the fossil into the collections.

And it's at that point, that the research truly begins.

- Hello, folks.

It's me, The Conductor.

Today the Pteranodon Family is deep in the Earth looking for the perfect spot to build an underground train station.

So come on along with me on the Dinosaur Train.

All aboard!

[upbeat music] ♪ ♪ - Nice stack of fish-wiches, Don.

- It's really swaying.

I bet you can't add one more leaf.

- Uh, Don-- - Ah, a teetering tower of treats.

Kind of reminds me of the layers of the Earth's underground, Mr.

The Don.

- That's what I was thinking, Mr.

The Conductor.

- I can see the Earth's layers-- the crust, the mantle, more mantle, then the core.

- Right.

That's where I live.

And that's where I take vacations.

- Here comes the Drill Train, drilling a hole way down to the center of the fish-wich Earth.

- Uh, Don, somehow the Drill Train makes less of a mess.

- [chuckles] - Mmm, tasty.

Okay, this has been fun.

I'm ready to head back up to the top.

Shouldn't we be getting home?

- What?

Shiny, first we have to go to the center of the Earth.

And we're almost there, right?

- No, we're not going close to it.

- Don, listen.

We're not going to the center of the Earth.

- You don't know everything, Tiny.

- I didn't say I did.

But Mr.

Conductor just told us we're not.

- Maybe he changed his mind.

- I know.

Let's go to the Passenger Coach.

I'll show you just how far we are from the center of the Earth.

It'll be a layered discussion.

[chuckles] Follow me.

Like Don's stack of fish-wiches, this globe shows us the layers that make up our Earth-- the thin, solid outermost layer, the crust, the denser, deeper layer, the mantle, and, finally, the really dense, extremely hot core.

- Let's go there--the core, the center of the Earth.

- It's super-duper-double-duper hot there, Don, as hot as the sun.

- Fine.

We won't go in it.

We'll just stand outside of it.

- It's much too hot to go anywhere near the inner core, Don.

Now, here's where the Drill Train started, and here's where we are now.

See?

Still pretty close to the Earth's surface.

- Is this where we're going next?

- Uh... [clears throat] [whispering indistinctly] - Actually, we're going to a different area, somewhere I've never been.

But I've been told it's the perfect place to explore for Nature Trackers.

- Ready?

Okay.

kids: Go, Nature Trackers!

[all cheering] [rumbling] - Shiny, I'm proud of you.

I know that when we first started this trip, you were nervous about being underground.

But now you seem fine and dandy.

- Thanks, Dad.

I do feel fine and dandy.

It's weird, though.

I mean, I can't see the sky.

And I can't even fly up in the air whenever I want.

Plus, there's all that rock over our heads, and under our feet, and on every side all around us, so much rock everywhere.

- [gulps, chuckles nervously] Yeah, I hadn't really thought of it that way.

- But none of that really bothers me anymore.

Oh, well.

- [shaky voice] Yeah, tons of rock above us, below us, on all sides, we can't fly out.

Oh!

- Deep breaths, Mr. P. Calm, breathe.

- Mr. Pteranodon, as a Necrolestes, I live underground-- always have, always will-- and nothing bad has ever happened to me.

You have my word, okay?

- [muttering] [train grinding, crash] - Oh!

Ah!

Is the train broken?

Are we stuck?

- It's okay, Mr. P. - I knew it, we're stuck!

- The train is broken!

We're stuck!

- I knew it!

- Everything is gonna be okay.

- Friends, please, listen, we're not stuck.

The Train isn't broken.

We stopped because we're here.

- Oh, right.

[chuckles] I knew that.

[chuckles] You got to stay calm, pal.

- It's Nature Trackers adventure time, underground!

Let's discover some treasures in the Earth's layers.

[all cheering] - Let's get into a deep hole!

kids: Yay!

Come on, let's go!

- This is what I told Mr.

Conductor-- many layers of the Earth are full of fossils.

- Who remembers what a fossil is?

- Old bones of different animals.

- And leaves and even footprints and leaf-prints of things... both: Are preserved in rocks.

Rawk!

- I love fossils, don't I, Buddy?

- Yep.

And so do I. I even brought a fossil from home for good luck.

This is a trilobite, a really old fossil.

It's the best one I have.

all: Ooh.

- So, Mr.

Conductor, can we be Nature Tracker Underground Fossil Hunters?

- You took the words out of my mouth, Tiny.

Now, remember, Fossil Hunters, look in the layers of sediment-- the older, broken-apart rocks.

That's where the fossils are.

- Look, here are some ammonites-- fossils of animals that actually lived in the ocean.

- The real ocean, down here?

- Well, Don, millions of years ago, fossils of ocean animals were buried at the bottom of the ocean.

Then the fossils were all pushed down into the Earth to where we are now.

- So there are fossil sea shells all over the place down here.

- What?

Shells?

Real shells?

- Ab-so-tootly-lutely, Shiny.

Okay, Fossil Hunters, let's start hunting.

- Who knew shells were underground, especially this far down?

Not this Pteranodon.

Show me some shells.

- Kids, as you hunt, you can put all the fossils you find in this cart.

Then I can wheel it onto the Drill Train.

[soft music] ♪ ♪ - Hey, my head's stuck.

Would someone please pull me out?

- [grunting] - Whoa!

Whoa!

[grunting] - [gasping] Oh, no!

That was my best fossil!

My good-luck trilobite!

- Oh, no.

I'm really sorry, Buddy.

It was an accident.

- Yeah.

- But I will help you find a new one.

We'll just look around, there's tons of fossils here.

- Okay, tha--thanks, Don.

- Well, it's time to get back on the train, Nature Trackers.

- Wait!

We can't go yet.

Buddy's lucky trilobite fossil broke, and we have to find him another one.

- Actually, Tiny, I'm pretty sure there aren't any trilobites here.

- How do you know that?

- All the fossils here are from a more recent time period, and I've learned after many years of digging that you don't find fossils from different time periods mixed together.

- Oh, too bad, Buddy.

That's just how layers work.

- Oh, but you know what?

Since we're already underground, I know a place where Buddy can maybe find another trilobite fossil.

- Really?

- We just have to drill down a bit more, to the fossils of an older time period.

- [sighs] Drill down?

I mean, of course!

Drilling down!

Sounds great!

[chuckles] - Can we please go to Natasha's deeper fossil place, Mr.

Conductor?

kids: Please?

- Hmm... of course!

How could I say no to an opportunity to explore more?

[all cheering] [rumbling] - Yes!

Closer to the center of the-- - Don't say it, Don!

We're not going to the "you know where."

- Actually, the place we're going is called Fossil Alley.

kids: Fossil Alley!

- Where we're going to find Buddy another lucky trilobite.

Well, we hope.

Trilobites can be hard to find.

Any idea why, Buddy?

- I have a hypothesis.

Trilobites are really old.

They're from a time period long ago, so they're probably deeper in the Earth.

- That is one excellent hypothesis, Buddy.

You're onto something.

Older fossils are harder to find because they're deeper in the Earth.

Then there's the Law of Superposition.

- Super-po-what-chin?

kids: Superposition.

- Oh, superposition.

Got it.

- What does it mean, Mr.

Conductor?

- Well, we know that fossils are found in different layers.

The Law of Superposition means that when we see a stack of rock layers, the oldest rocks are usually on the bottom, and the younger ones are on top.

- So there are layers of older and older fossils?

- Bingo, Buddy!

As the older layers of fossils got buried deeper and deeper, new layers formed above them.

[bell chiming] Oh!

We're here!

Next stop--Fossil Alley.

[train grinding] - Aah!

[sighs] Calm, yes.

I'm perfectly calm.

Everyone else okay?

- We've just stopped, Mr. P. I've gonna have to have those brakes checked.

Everyone, let's explore!

all: Fossil Alley!

[cheering] - All right, this is the place.

Let's look for ancient fossils.

- Rawk!

Show me more shells.

- Fossil, I think it's a fossil, Swirly fossil, long fossil, ooh, super-swirly fossil.

- Oh, trilobites.

Where are you, trilobites?

- Found one, Buddy?

- Oh, not a trilobite.

Keep looking, Buddy.

- [sighs] I guess I'll never find a-- Wait.

Is that a...?

all: Trilobite!

- [gasps] It is a trilobite-- a beautiful one.

- Hooray!

We found a trilobite.

- Not just a trilobite.

- Whoa.

Looks like there's enough trilobites for everyone.

[all cheering] - How do you like it, Buddy?

- It's perfect.

It's even better than my old one.

- Yeah.

This one's gonna be even luckier.

Whoo-hoo!

- Okay, Nature Tracker Fossil Hunters, all aboard!

[all cheering] - Thanks for taking us to Fossil Alley, Mr.

Conductor.

- Anything for my favorite passengers, Buddy.

- Don't forget Natasha.

She told us about Fossil Alley.

all: Hip, hip, hooray!

- You know, I understand there may be one other spot that's even more perfect... deeper down.

Should we all go take a look?

- I--Well... - Yeah.

Let's keep it going.

Let's drill down deeper till we find out... all: ♪ What's at the center of the Earth?

♪ - Hi, I'm Dr. Scott, the paleontologist and these are T. rex footprints.

Paleontologists have discovered thousands of dinosaur footprint fossils.

They've been found on every continent.

- Dinosaur footprints.

- Sometimes we just find one footprint, and sometimes we find a long series of footprints called "track ways."

Fossil track ways tell us how dinosaurs moved.

Tracks tell us that disaurs stood upright.

with their feet close together, and since we don't find many signs of dragging tails, we know that dinosaurs held their tails in the air.

- That's cool.

- Paleontologists have also found track ways of sprawling crocodiles... [crocodile snarling] and slithering snakes... [snake hissing] and hopping frogs.

[frog croaking] Of course, animals living today make tracks too.

You're probably seen some right around your own home.

Hey, I've got an idea.

Get outside, get into nature, and make your own footprint discoveries.

- We love playing games.

- Like All Aboard!

You can play, too, online at pbskids.org.

- And lots of other games!

- There's so much to learn about all kinds of dinosaurs.

- Go to pbskids.org.

- ♪ Dinosaur Train ♪ - ♪ Dinosaur Train ♪ - ♪ Dinosaur Train ♪ - ♪ Dinosaur Train ♪ - ♪ Dinosaur Train ♪ - ♪ Dinosaur Train ♪ - ♪ We're gonna ride... ♪ - ♪ Ride, ride, ride, ride ♪ [train whistle toots] - ♪ The Dinosaur Train ♪