Hey everyone.

My name is Chris Anderson, and I'm in Shenandoah National Park, home of the Blue Ridge Mountains.

The rocks here are old, older than the trees.

Seriously.

The youngest rocks in this park date from over 500 million years ago.

Back then, trees hadn't evolved.

So what led to the formation of all these rocks half a billion years ago?

And what forces created the Appalachian Mountains?

And why am I always so hungry?

Today, on OutSCider Classroom, we will answer two out of these three questions, which, as the late, great poet Meatloaf once said, ain't bad.

[Intro music] [Music] Shenandoah National Park protects one of the most beautiful stretches of Appalachian mountains in the entire country.

There's red oak forests, black bears, and waterfalls.

But it wasn't always like this.

When the sandstone at the top of these mountains formed almost 500 million years ago, most of life was confined to Earth's oceans.

In fact, in those rocks, you can find trace fossils of worms that burrowed their way into the sand.

So how did we get from sandy seabed to rolling hills and lush forests?

There are three important geologic concepts we need to understand if we want to know how the Appalachian Mountains formed.

Important geologic concept number one, the Earth, much like ogres and parfaits, is made of layers.

There's a solid iron inner core.

The liquid iron outer core, the gooey, sticky molten rock mantle and the crust, the thin, brittle outer layer of the earth.

Kind of like the shell of an egg.

That leads me to important geologic concept number two, the Earth's crust is broken up into sections called tectonic plates.

Tectonic plates, tectonic plates, tectonic plates, tectonic plates.

The tectonic plates fit together like a puzzle, so you can imagine them kind of interlocking and floating on top of the molten rock mantle.

That molten rock flows a bit like honey, but there's a pattern to it.

It rises as it's heated near the core, only to sink again as it cools, creating a circular current called a convection current.

That brings us to important geologic concept.

Number three.

Currents in the mantle are what caused tectonic plates to move, and those plates bump and grind past each other as they roam about the surface of the earth.

And there's nothing wrong with a little bump and grind.

That's where all the action is, geologically speaking.

Some plate boundaries, they're kind of pushing past each other.

Scientists call those a transform boundary.

Other plates, they're moving away from each other.

Scientists call those a divergent plate boundary.

But neither of those plate boundaries build the biggest mountains in the world, like the Appalachian Mountains used to be.

For that, let's check in with my friend, Doctor Folarin Kolawole.

The convergent boundary is a location where two tectonic plates are moving towards each other and smashing against each other.

The two tectonic plates colliding against each other have two options.

Each one of them have two options.

One is either to go up or to go down beneath the other one.

And what determines where to go is basically the density of the tectonic plate.

If it's a very dense and heavy tectonic plate, it's going to sink into the Earth, into the mantle, into the Earth's mantle, underneath the other plate.

And if it is less dense than the other plates, it has a tendency to be to go up while the other plate goes down.

And if both plates have similar densities, they would likely collide against each other and they would both go up.

So right here, we're within the Appalachian Mountains and, we know that these rocks, have accommodated a convergent plate boundary in the past because we can see a very classic evidence of that right here.

And that evidence is the folding of the rocks.

When you see fold in the rocks, it suggests that, the rocks are being pressed against each other.

So typically we would normally assume the rocks are laid down in horizontal layers.

And if you see that the horizontal layering has been altered by tilting and folding, then that tells you that the rocks are being compressed, due to plates collision.

And right here we see folding in these rocks.

So here we have the wiggles right there we have that.

And that tells us that this rocks have been squished together.

We also knew that the Appalachian Mountains were built up, about 350 million years ago.

But these rocks are older than that.

We know these rocks are about 1 to 1.2 billion years old, and the fact that they've been squished together and pushed up within this mountain suggests that, you know, we definitely had collision right here.

Check out this sandstone.

It formed over 500 million years ago in an ancient seabed.

So how did this rock go from under the ocean to on top of a mountain?

The same forces that built the Appalachian Mountains pushed this rock up.

Think about it.

You're talking about continents smashing together.

That's billions of pounds of pressure being exerted over hundreds of millions of years.

Pretty amazing that you can find evidence for this whole convergent plate boundary mountain building era right here in Shenandoah.

The Appalachian Mountains are also a great place to learn about weathering and erosion.

When these mountains were at their peak, they looked more like the Rocky Mountains.

Tall, rugged, and, well, rocky.

Over time, wind, rain, and eventually plants and other living things broke down the rocks through process called weathering.

Streams and rivers then eroded or transported those sediments down through the valleys and eventually out to the Atlantic Ocean.

Softer rocks like limestone were broken down and carried away, leaving us with harder rocks like sandstone, granite and gneiss.

What were the imposing and tall peaks about 200 million years ago or now?

The gentle rolling hills we enjoy today.

But geologic processes take a long time.

Tectonic plates only move a couple of inches a year, and weathering and erosion can take thousands of years to put a dent in a mountain.

But with their powers combined they are Captain Planet.

No, no.

With their powers combined, they shaped the surface of the planet.

[Music] Shenandoah is a great park to explore.

There's lots of rocks that tell stories about the Earth's history from millions or billions of years ago.

But that's true.

No matter what rock you're looking at, see if you can learn to read the stories in the rocks from where you live.

If you do come to Shenandoah and go a rock huntin, make sure you leave them where you found them.

If everyone takes a rock, eventually there won't be any left for others to enjoy.

Plus, it is illegal to collect rocks in a national park.

Actually, it's illegal to collect anything in a national park, come to think of it.

Take a picture and ask a ranger to help you identify it, or see if they can tell you something about the Earth's history, but leave it where you found it.

[Music] Well, until someone gets a Tardis or a DeLorean to work, we can go back in time rocks are our best piece of evidence for learning about our planet's history.

You can learn what was happening on Earth, millions or even billions of years ago.

All you need to do is know where and how to look.

Lucky for us, I brought a ringer.

Doctor Chuck Bailey literally wrote the book on Shenandoah Geology and he's going to teach us a little bit about how these rocks formed.

I'm Chuck Bailey, I'm a structural geologist at William and Mary.

The rocks that are sort of underfoot are very old, granitic gneisses.

So these are rocks that originally were granites.

They formed as magma cooled deep underground, but that magma was later sort of sheared under very high temperatures.

And that turned it into a metamorphic rock that we know is as a gneiss.

And you might be able to see in the camera images, there's a bit of layering in this rock.

Layering develops in metamorphic rocks in a way that you might think about as, as you make candy or taffy.

The material is pretty soft, and as Earth forces shear and squeeze these rocks, different minerals are effectively dragged out into layers.

So it's a secondary feature that comes as the rock is deformed and metamorphosed, much like we might do with Play-Doh, or even, cookie dough.

The change from an igneous rock to a metamorphic rock is one that's sort of hard to understand sometimes, because it happens in places that we can't see.

These granites form many, many miles underneath the Earth.

And then later, there was a collision between vast continents over a billion years ago.

And these rocks were effectively caught up in the vise, that was squeezing, as these different tectonic plates were colliding.

These rocks are generally identifiable because, many of them have a certain layering that's developed to them.

And then you've got to be able to identify a few different minerals in these rocks.

And one of those is feldspar.

And hopefully you can see here the light white colored mineral is a feldspar.

And it's distinctive.

It's different than quartz which is the darker mineral in here.

But these metamorphic rocks have both feldspar and quartz.

And if you can identify those you're well on your way to identifying the metamorphic rocks.

So the rock behind me is kind of a gnarly outcrop of green stone.

And this green stone is originally it would have actually formed as lava, very hot lava flow, basaltic in composition, that flowed out over the surface of the earth here in what would eventually become Shenandoah National Park.

The granitic rocks that we saw at our first stop, they would have cooled literally over thousands of years.

And during this cooling, you would have grown large mineral crystals, whereas this lava flow was erupted rapidly and it cooled very rapidly.

Therefore, the grain size, the the texture in the crystals is really microscopic, very hard to see with the naked eye.

The green stones, these metabasalts in Shenandoah National Park, they flowed out over the landscape about 550 to 560 million years ago.

That's a long time.

But that's half the age of the rocks we saw originally.

These lava flows extend from what is now Pennsylvania to central Virginia.

They covered thousands of square kilometers.

And what was happening that effectively, the crust in this region was starting to be torn apart by tectonic forces.

And that allowed magma from very deep in the mantle to rise, melt and spread laterally across the landscape.

The primary thing to look for is that the the green stones, the metabasalts, are, fairly fine grained.

You don't see large crystals in them, and they're almost invariably going to be composed of a light green to dark greenish mineral.

So those are the two characteristics that I would look for.

We are on an outcrop, very small but very exciting outcrop on the side of Bear Fence Mountain.

And the rocks that I'm sitting on that I have my hand on, they're actually sandstones and conglomerates.

They're made up of little pieces, little chunks of eroded granitic gneiss.

And if you remember back to our very first stop, we looked at the very old oldest rocks in the Blue Ridge, these granitic gneisses.

Well, at some point those rocks were eroded and then deposited as sediment.

And in this outcrop, there are delicate layers of sand and mud, and then in some places, very coarse grained gravel, all bits and pieces of that granite.

So this is a sedimentary rock.

Already today we've seen igneous rocks and metamorphosed igneous rocks.

And here we're seeing a really lovely example of a sedimentary rock, albeit slightly metamorphosed.

It still has all the hallmarks of sediment that is original layers and original grains that are preserved in this rock.

So the sediment that's preserved in this outcrop was clearly formed by the erosion of the granitic materials.

And I can imagine a landscape where we had bare granitic outcrops sticking up, and that the granite would slough off and fall down.

And streams, rivers, would then sort of push that sediment down into valleys, and it was there in these valleys with running, flowing water, that the sand was winnowed and sorted and turned into these little layers and laid down as sediment.

So that the rock layers that we see here are below the green stones, that is, they formed prior to the eruption of the lava flows.

So we know that these rocks must be older than about 570 million, and they're younger than the 1 billion year old rocks that are below us and are bits and pieces in here.

So our understanding of the exact time when this formed is, you know, not as well known as we would like.

One of the things I can do is if I rub my finger across this, I feel the grit from those little pieces of sand.

They're rounded and angular pieces of feldspar and quartz.

So it has this sort of grittiness to it.

It also contains the feldspar and the quartz that we've seen earlier.

But if you look closely, especially with a magnifying lens, you'll notice that they're somewhat rounded.

They're not interlocking.

So it has the texture of a sedimentary rock.

You don't have to come all the way to Shenandoah to find awesome rocks.

I bet you can find really cool rocks where you live or go to school.

See if you can discover which geologic forces created the rocks near you.

You never know what you can learn about the Earth millions of years ago, just by taking a look at the rocks underneath your feet.

[Music] One of the most popular ways to explore Shenandoah is by taking a trip on the Skyline Drive.

For over 100 miles, the road winds through the Blue Ridge Mountains, giving visitors some of the best views in the park.

But why is this road here and how did it get built and who built it?

To answer those questions is my friend Stephanie Hammer, a social studies teacher at William Monroe Middle School.

Not only is she an awesome teacher, but she helps preserve and share the park's history.

Hi, I'm Stephanie Hammer.

I teach at William Monroe Middle School; social studies, U.S.

history.

Skyline drive was built in the 1930s.

First it was built as a road, a ridge road along the mountain top by President Herbert Hoover.

He had a fishing camp which is still in the park.

And he would come here, and so he was familiar with the area.

During President Roosevelt's presidency with the New Deal program, they created the CCC, Civilian Conservation Corps, who then took up the job of building Skyline Drive as we know it today.

The CCC hired young men in their early 20s.

They had to be unmarried so that part of the money would also help support their families.

So they would live in the park and they would get paid $30 a month, $5 they were allowed to keep, and $25 was sent home to support the families.

In western United States, like I said, there were parks that were national parks that were built, but there was nothing in the eastern states.

And so the government was looking to build a park somewhere in the east.

Virginia advocated quite a bit to have it built here, Shenandoah National Park.

And also, they were looking at Smoky Mountain National Park.

And so it provided for the people.

And there were about 40 million people living in cities in the eastern states at the time.

And it provided a way for them to go and get some outdoor recreation, go for a drive, which was very popular at the time because everybody was buying cars.

And it was just a lot more accessible in distance for people.

There were families on both sides of the mountains.

They interacted with the communities that were at the foot of the mountains or part of the community that was at the foot of the mountains.

They were known as mountain folk, and they farmed.

They raised beef and cattle.

There were copper mines.

There were people who made pottery, and they were a thriving community.

They were quite successful about what they were doing.

They were organized.

They had churches, they had schools.

So they were people that enjoyed and felt like they were living the American dream up in the mountain side.

So it completely changed their lives.

Those that were living on the mountain, they were forced to leave or told they had to leave.

Some left, some volunteered to leave.

Some were needed to be forced out.

There were a few individuals, because of their age, that were granted the right to stay in their homes until they lived out their lives, but a lot of people felt like they were misrepresented, and they were disappointed in what the government was doing and weren't really sure where they could go because they didn't have land to sell, they just needed to get up and leave.

So it did impact their lives quite a bit.

Many students still live in the mountains.

And so they're very familiar with the park.

They come here with their families, they go for drives.

They they go on picnics, they camp, they hike.

And so they're familiar with the park.

When I teach the Great Depression, we talk about building of Shenandoah Park because we talk about the New Deal programs.

And so I show pictures of the park being built, including the stone walls.

And when they see the stone walls, they recognize everything right away.

And it brings it full circle for them because they feel like they're learning something about their own community and a place where they've been.

I think they understood.

I think they took away the understanding that history changes and that where they live, and they only know there's a park there.

They learn that at one point in time it was different.

The Civilian Conservation Corps employed 3 million young men during the Great Depression, working on projects from planting trees to maintaining trails to controlling mosquitoes to infrastructure projects like the Skyline Drive.

Many of these projects that are national parks still today.

Sadly, Congress ended the program in 1942.

World War Two had broken out, and workers were either drafted or otherwise engaged in the war effort.

But that doesn't mean there aren't still great organizations that maintain and protect public lands.

Some states have their own conservation corps that do much of the same work the original CCC did, but in state parks and wilderness areas.

There's also great city and county wide programs that get young people outdoors and involved in conservation.

See what's going on in your community and see how you can get involved.

[Music] I'm in the mountains of Virginia and we're in the mountains of Scotland.

Hi, I'm Kennedy and I'm Abby.

And you know what's crazy?

These are the same rocks that we see in the Appalachian Mountains in Kentucky.

They were formed at the same time and by the same tectonic forces.

So how did these mountains get separated by over 5000 miles of ocean?

[Music] Shenandoah National Park protects more than 300 square miles of the Blue Ridge Mountains.

They're part of the Appalachian Mountains that run up and down the eastern United States.

From Georgia to Maine to Scotland?

[bag pipes] How's that possible?

The Earth's crust is broken up into pieces called tectonic plates.

And just below the crust is the mantle.

The sticky layer of molten rock that moves and flows a bit like honey.

But there's a pattern to its movement.

The molten rock rises as it's heated near the core, only to sink again as it cools, creating a circular current called a convection current.

These convection currents cause the plates above them to move around.

You can imagine pool toys floating in water and moving around with the currents.

It's basically the same thing scientists call the moving of tectonic plates across the Earth's surface.

Continental drift.

Continental drift happens pretty slowly.

The plates only move a couple of inches a year, so it's really hard to see or even measure in the course of human lifetime.

But give them a couple hundred million years.

Those plates really get around.

Around 400 million years ago, the tectonic plates of Africa North America and Europe began to collide, creating the original Appalachian Mountains.

At their peak, they were likely as high and as dramatic as the Himalayas.

It was this convergence of three tectonic plates that created a mountain chain across three different continents eastern North America, northern Africa and northern Europe.

They're geologic triplets.

But after a couple hundred million years, the currents in the mantle changed and the continents began to break apart.

I guess it's hard to be together for that long.

Heck, the Beatles barely made it through the 60s.

So how do we know any of this?

How do we know that the mountains just weren't created at the same time?

What's our evidence for continental drift?

We came to the Lochaber Geo Park and talked to the director, Ian Parsons, to find out.

[Music] Now, these rocks are about 500 million years old.

So how exactly can we tell how they were once connected to the Appalachian Mountains that we see in the United States?

By matching up the rock types and their chemistry and the way they're folded and deformed.

So we can be really confident they're all part of this mountain range, which not only goes down the east coast of North America, but it goes northwards right to the northern tip of Greenland.

Wow.

And the Caledonians, as we call them, which is a name given to them by the Romans.

So know we all know the three basic rock types igneous, metamorphic and sedimentary.

What kind are we mostly seeing around here?

Well, that was mostly this is almost all igneous rock.

And the bottom of this cliff here.

But the thing's called geological silts.

They've inject been injected, flying across the ground, and with one sandy layer with sandy layers behind them.

But the very top of this cliff above the grassy bit, those are lava flows.

And they were most some of them were deposited, from volcanic ash clouds and so on.

These are actually about 420 million years old.

This caldera formed.

And an extraordinary thing about, Glencoe.

It's where it's active caldera here is known all over the earth.

This was the first Ancient one recognized in this geological record by the early mappers.

So it was quite a discovery, too.

They interpreted this as a caldera quite correctly, but it was a completely new concept, a historical caldera.

So these mountains, though they're 5000 miles apart, they were formed by the same tectonic forces and they show physical evidence of continental drift.

So, yeah.

Ian, thank you so much for talking with us today.

Thank you.

- Okay.

- Back to you, Chris.

Every day of every year for the last 200 million years, the North American and Eurasian tectonic plates have been moving away from each other.

How do we know?

In the middle of the Atlantic Ocean, along the seafloor runs a ridge that we've cleverly named the Mid-Atlantic Ridge.

As you move away from the ridge, the rocks get progressively older.

Think that's weird?

So did geologist Harry Hess before Hess came along.

Continental drift was a fringe theory for kooks, then Hess noticed this strange pattern in the rocks.

Turns out that's where tectonic plates are moving apart.

As the plates separate, magma comes up from the mantle cools and new crust is formed.

It's awesome because we can see new crust being formed in real time, and evidence for continental drift.

Earth's surface is constantly changing, and continental drift is a big part of that.

The tectonic plates continue to move today.

Who knows where they'll end up in 100 million years?

But it will be the same geologic processes driving their motion convection currents in the mantle, forcing the tectonic plates to move around, bumping into, sliding past, or moving away from each other.

It's how we get mountains and ocean ridges and a ton of other amazing features on Earth.

Well, that's our show.

Thanks for watching.

Now, if you'll excuse me, I have some metamorphic strata to analyze.

We'll see you next time on OutSCider Classroom.

[Music] Major funding is provided by the National Geographic Foundation.

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