It has been our nation's greatest physical barrier.

Its looming presence struck fear into the hearts of men and women.

It caused our most famous case of cannibalism.

It produced the world's richest gold mines.

It was the cause of civil war battles.

It's the Sierra Nevada.

Funding for In the Americas with David Yetman was provided by Agnese Haury.

♪ music ♪ ♪ music ♪ The completion of the Union Pacific railroad represents one of the greatest accomplishments in American history.

It had to be built up and over the Sierra Nevada.

That's just one of many chapters in the history of our greatest mountain range.

It's a monster range, 450 miles long around 50 miles wide, cracked with canyons and rivers and 14,000 foot high jagged peaks.

Until late in the 20th century no one really understood why this massive block was even there.

My brother Dick is a geologist, I asked him to come along with me to help understand the Sierra Nevada.

He and I both knew that one man came up with the story that finally unfolded the range's secrets Eldridge Moores.

..That contains a lot of the material that I had to remove from my office at the University and there's a lot of things I didn't want to get rid of so I...

Including the maps I'm carrying.

Including the maps that we're carrying.

Oh, this is great, wow.

Hey you've got a tectonic map.

You're expecting us.

There's the plates.

This is earthquakes.

So all the earthquake zones are in black.

Yes.

So the blacker, the more earthquakes.

That's correct.

You see earthquakes on the west side of California associated with the San Andres fault and we see earthquakes along the east side of the Sierra Nevada associated with the zone of earthquakes that one sees from there into Nevada, but the part that we live in here in the valley and the western slope of the Sierra Nevada is relatively earthquake free.

It's now called the Sierra micro plate.

There's something over here that I think you should see, it's an animation of the historical development of the western margin of the United States or western North America and including the development of the San Andres, but the animation was done by Tanya Attwater at Santa Barbara, but let's take a look at it here.

We start off with three plates.

We have the pacific plate to the west then the Farallon plate on the ease side of that and then on the east side of the Farallon plate is the North American Plate.

So I'm going to just run this.

Fire away.

It starts at about 38 million years and we have a temperature line here that tells you what the age is.

So here we go.

You can see there's the Farallon plate dividing into two.

The San Andres fault begins right in here and it expands at length, one tip moving to the north west and the other tip moving to the south east and finally it ends up going into what's now the Gulf of California and dividing that from North America.

This is plate tectonics in action.

It's nice not to have to wait 38 billion years.

This brings it alive.

Yes.

I think it's about 1 million years per second Haha.

Good work.

Now I know you're a musician and music has been a great part of you life, cause I've seen you in photos with your cello, but why is geology so important for you?

Well geology is the most important subject for every person to know.

It underlies everything.

It underlies our landscape...

Literally.

Literally.

It provides the basis for all our resources.

It forms the basis of our economy.

And it's important for our well-being and for our food, our agriculture and it's just the most important science that everyone should know something about.

Well I'm not going to dispute this but you're going to have to demonstrate this to me.

Well, I will be glad to do that.

Before we could even begin to understand, I had to see the Sierra from above.

I decided to follow the route well known to Indians for centuries.

The route European settlers chose, which often got them into trouble.

The Sierra Nevada is so vast, you can't appreciate its size from the ground.

We're flying out of Sacramento to get the big picture.

I can see the interstate down there and some lakes, but those lakes are all reservoirs.

The forests are beginning and now the hills are ramping upward toward the east.

I can see why they call the western part of the Sierra Nevada a trap door.

The railroad is one long series of switchbacks, especially now that the slopes are getting steeper.

It's pretty clear where miners gouged out a canyon from flat lands, 150 years ago.

Now that's the famous Emigrant gap where settlers had to lower their wagons down on one side and hoist them up on the other.

Those tunnels are snow sheds.

Obviously the highway builders followed the same alignment as the railroad.

And here we are near the top.

Those are natural lakes and snow.

This landscape is carved by glaciers.

There way in the distance is Lake Tahoe.

Now that I've seen the range from on high, I can better appreciate what's on the ground.

First, Eldridge takes us to a very well known site in Nevada just to demonstrate how the Sierras have shaken the earth.

You're telling me that this is a fault and I think I believe you but why do you think it is Why I think it is, is because you have this huge surface here that's basically, essentially flat.

It's like a plain but it's a plain that's oriented sort of plunging in that direction to the east.

And you can see some places the surface is polished and..

Okay.

Okay and you can see streaks on the surface.

I see a long line right up there.

Yeah that long line is actually, you're looking along the plain of the fault and that's actually, there's are a whole series of flatish partings in this sort of fault zone.

That side is going up, relative to this side, which is going down.

And this is only produced by earthquakes, is that correct?

This is only produced by earthquakes.

It's moving at about 1-2 millimeters per year and this fault or the general fault has had several earthquakes on it over the last century or century in a half.

Here is some more of these streaky things... Yeah oh that's pretty graphic right here.

You can almost see the.

This part moving down has just scraped this wall.

The upper side moving down has scraped this stuff, yeah.

Dave: This is going to go up, up up, and that's how mountains get built out of faults.

Correct.

This is a wonderful example of how the Sierra Nevada got lifted up into the air 6, 000 ft above the base of the valley.

After this famous rock site, it's back to the west side to follow the gentle way up into the mountains.

So I look ahead and behind and this to me defines flat, flat, flat, but you say I'm wrong.

Yeah the congressional act that gave rise to the railroad building stated that the builders would get three times the money when they were building in the mountains.

They convinced Josiah Whitney, who was then the state geologist in California, to specify that this creek right here, Arcade Creek was the beginning of the Sierra Nevada and so Lincoln actually issued a proclamation in 1864 to state that Arcade Creek right here was the beginning of the Sierra Nevada.

So from here on it's Sierra Nevada.

From here on it's Sierra Nevada and from here on it was three times the amount of money that they got just from the other side of the creek.

Eldridge Moores was the first to locate some strange rock formations in the Sierras.

He explained to me the importance of sheeted dykes and pillow lavas.

I didn't realize it but they came from volcanic activity in the ocean bottom thousands of miles to the west.

And here they are a few thousand feet up in the Sierra Nevada, seeing them Eldridge realized that the Sierra Nevada was not just a big bulge in the Earth.

Much of it came from far away, part of a raft of cosmic proportions.

You've taught me that where there are sheeted dykes pillo basalts are never far away.

Yes that's correct and here we have a nice example of some pillow lava in this road cut.

These are quite nicely developed and you can see the bulbous tops and the sort of flattish or indented bottoms and they tell you that the tops and the orientation of the lava say that the original horizontal surface is about titled about 40 degrees here.

Only a few miles away, Eldridge shows me another heritage of colossal mountain building.

The zone where enormous blobs of molten magma forced their way into the terrain above and shoved that land far up into the sky, where they met is called the contact zone.

For years I've heard you and other geologists talking about contact zones and now here's one near the freeway and you're really going to show me what it is.

Yes I am.

You're about to step on it.

It's...

This gray stuff.

This boundary between the lighter colored granitian rock on my side of this boundary and the darker colored metamorphous volcanic rock on the other side.

Oh right.

The boundary, how old is it?

The metamorphic.

The metamorphic rocks are about 200 million years old.

And where you're walking?

And where I'm walking, these granites are about 80- 100 million years something like that.

Oh haha okay.

The Sierra Nevada collects snow and rain and sends them downstream as rivers.

Big cities covet that water and engineers love to collect it and store in a dam.

We're standing on Orovillle dam here in the northern, northwestern part of the Sierra Nevada.

They dammed the Feather River and as I remember it was part of the California water project back in the late 50's or 60's to bring Sierra Nevada water to the thirsty, hungry water, hungry south of California.

What's the upshot of that?

The Sierra Nevada provides the water.

Right now it's mostly as snow and it's snowmelt.

One of the concerns is, as the climate changes, the precipitation will come as rain and the storage possibility of snow will diminish.

Without the Sierra Nevada, L.A could not survive.

L.A needs the northern Sierran water.

That's for sure.

Don't be deceived by the freeway that speeds traffic by.

It was a tough crossing 150 years ago.

Why were immigrants undergoing such hardships to get here?

Most of them came lusting after gold.

This is the gentle western slope of the Sierra Nevada.

Once the immigrants had crossed the pass, it was easier but by no means easy.

They followed down this ridge where we see the railroad and the freeway now and reached roughly here.

But this place is called Emigrant Gap, once they reached here, somewhere in this place they had to lower their wagons down by rope or cable.

They could make it across this pretty valley but they couldn't go downstream, because the glacier stopped here and just below here it gets very, very rough.

They had to raise their wagons by cable or rope again on the other side.

Once they reached the top, it was relatively smooth sailing all the way down to Sacramento, but this was a major obstacle.

When the settlers started coming through of course, there were no roads, there were only tracks or trails and one of the problems with wagons was of course that they could not go on side hills.

They had to go straight up the hill or straight down the hill otherwise they would tip over, so at first they would unload the wagons and they would pull them up with teams of oxen from the top.

One wagon at a time and of course they had to hand carry all the goods from the wagons up to the top where they had gotten the wagons.

Later on a road was built that would handle wagons and that was used in the latter part of the 19th century.

Some of the gold was plastered right on the surface.

Most of it ended up being mined hydraulically.

The evidence, the scars are still there and are still evident many miles down stream.

The gravels in this hillside are not ordinary gravels.

These are gold bearing deposits.

They had so much gold that they attracted miners from all over the world by the hundreds of thousands.

The cliff behind me is a man made cliff created by gold seekers.

Prior to the gold rush and operations of the mid 19th century where the top of that cliff stands now, 4 miles across the valley it was level.

All of that material was taken out by hydraulic hoses of immense power and the sediments after the gold was removed washed downstream to fill in the delta 75 miles away.

Prior to that time, the Sacramento river was navigable 80 miles upstream to Red Bluff.

After, you couldn't get a row boat up that far.

Tales of free and fertile land swirled around the Eastern US.

Free land and free living.

How else can we explain parties like the Donner party who attempted cross the Sierras during the brutal winter of 1846?

They ignored warnings of scouts and Indians, thinking only of the green, promised land.

Snow stopped them in their tracks and only cannibalism enabled 48 of their party of 87 to survive.

The Donner Party was a group of settlers coming into California.

At Salt Lake City, they took a wrong turn and they took a route that took them over the area of vast salt flats, west of Salt Lake City so it slowed them down.

They got here in early November and they tried to get over the top of the pass here, but didn't succeed and decided that they would try again the next morning.

But in the night, a three foot snowfall came down and they were stuck.

They were stuck from early November essentially into sometime in February.

The main trial, of course, that the Donner party faced, while hold up below the summit on the east end of Donner Lake to the east of here, was starvation.

They ate all of their animals.

They ate all of the supplies they had.

They tried to hunt and trap and they had very little success in part because the snow was so deep that they couldn't walk anywhere.

They sent out relief parties over the hill to Sacramento and finally one did get through and the relief party came from Sacramento and came up and brought food to them, I think in late January or Early February of the following year.

Rumor has it that, they in fact they resorted to eating each other.

Starting first with the people who had died and perhaps then going on to ones that were still living.

The mortality rate has been reported to be about 50%.

It was a very famous incident and it actually changed the way in which people viewed getting to California.

Higher up towards the east we see the obstacles facing the engineers in the late 1860s, as they tried to finish the railroad.

Engineers alone could never have completed the job.

They needed a host of strong, smart and fearless workers.

Most of them were Chinese.

6,000 feet in the real Sierra Nevada.

We're walking on the very rail bed, you tell me, authorized by President Lincoln.

That's correct.

We're up actually very close to the tunnel that was driven through the Sierra granite in the late 1860's.

I think 1867.

This tunnel, that's behind us here, was perhaps the most difficult bit of excavation that the Chinese rail workers had to do.

And without their labor, their ingenuity, their abilities, this railroad would probably never have been completed at least not for a long time.

Not for a long time, I think that's correct.

They would've, it would've taken decades longer probably to finish the railway.

They call it the China wall, because the Chinese built it and they built it instead of having a bulldozer come along, which is the thing we do these days.

The Chinese actually built it out of large blocks and they're closely fitted.

They look like a fine piece of masonry.

The other reason was because at the time a number of people said 'oh the Chinese couldn't do something like this.'

And the foreman of the railroad, of the construction, I think it was Charles Crocker, was reputed to have said 'well, they built the Great Wall of China, they could probably build this as well.'

This wall was built in I think 1866 or 67.

Snows can reach thirty feet in depth in the Sierras.

How do you keep the tracks clear?

One imaginative solution, build snow sheds.

Snow sheds were built to prevent snow from piling up on the tracks so that the railroad could be continued to be used during the wintertime, during the time of great accumulation of snow.

They did have snowplows that they would use and occasionally the line did close down, but they tried to keep it open as much as possible throughout the winter.

The snow sheds were originally made of wood and that was the material that they had most easily available, cutting down all of the trees nearby but there are problems with that.

First of all, the wood is not as strong as concrete to withstand the tens of feet of snow that accumulate here and of course they were burning first wood and then coal in the locomotives and then the locomotives would spark, sparks coming of the locomotive smoke stack would catch the wood on fire.

They had a lot of trouble with tunnel fires or with snow shed fires and eventually they replaced them with concrete.

Once we are east of Donner Summit, we have to take a quick detour to our nation's prettiest lake.

It's something most of the workers on the railroad never got to see, but why is the lake there?

Eldridge helps me understand.

Lake Tahoe has always been the icon to me of the Sierra Nevada, but you're telling me that it's really not all in the Sierra Nevada, actually the Sierra begins here.

Yes.

Strictly speaking, the Sierra frontal fault is a fault that you see on the east side of the Sierra and that more or less continues with an active fault on the west side of Lake Tahoe underneath the water.

Lake Tahoe is about 6,200 feet elevation from the surface.

It's about 1600 feet deep, so the bottom of the lake is at about the same elevation as the Carson valley on the east side of this range, the Carson range.

So there are faults on both sides of the lake and all these faults are considered to be active faults.

Most geologists now thank Eldridge Moores for unraveling the secrets of the Sierra Nevada.

Most Californians, and come to think of it, most Americans should thank the Sierra Nevada and the colossal forces that brought it into being, for what it has done for California and for Californians, first it's gold, now it's cornucopia of food and its enormous economic productivity.

The Sierra Nevada, our greatest mountain range.

Brazil's landscape is most famous for its rainforests.

But, its coasts are home to some of the world's most extensive dunes of sand.

From an urban dune field in the city of Salvador, to a vast dune system called Lençóis.

Join us next time In the Americas , with me, David Yetman.

[music] [music] Funding for In the Americas with David Yetman , was provided by Agnese Haury.

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