"I'm surrounded by an army of caterpillars crawling northward from Mexico."

That's right.

This is the Basin and Range Geologic Province in the southwestern United States.

A U.S. Geological Survey geologist named Clarence Dutton wrote that amazing description of the Basin and Range in 1876 as he looked at a map.

The caterpillars he referred to were not real ones.

They were the dark, skinny blotches on his map that denoted the many mountain ranges in the province.

The ranges are all lined up, crawling, if you will, in the same direction.

Many of the ranges are wilderness, all of them different, rising to the high desert sun from dry lakes in the valleys between, a most peculiar land where the geology is right before you.

I'm Doug Prose.

This is "Doug's Geology Journal."

Let's go explore.

♪ ♪ Announcer: Funding for this program was provided by the National Science Foundation.

♪ Doug: The Basin and Range is the heart of the West, centered on the state of Nevada while touching on surrounding states and Mexico.

It is wide open, endless, and wild.

There are 160 mountain ranges in the Basin and Range and, in between, another 150 or so basins, or valleys, and it's gorgeous!

Some of the ranges are covered with sagebrush and grass, some with trees, like the bristlecone pine, the oldest living tree on earth.

Some ranges have very little vegetation, their rocky innards exposed to the sculpting forces of rain and wind.

In winter, the ranges are capped with snow as this is high desert country.

The basins bottom out in flat, dry lakes, or playas, baked dry to the hue of bone.

The extraordinary diversity of landscapes you encounter in the Basin and Range is due to a geologic force that is literally tearing the earth's crust apart here.

So let me draw you a picture to show you how this works.

As the earth's crust is stretched, it gets thinner and tears apart into parallel blocks.

The breaking crust is pushed up by hot rocks below, and alternating blocks rise up while those in between sink down.

After millions of years, the rising blocks become mountain ranges and the sinking blocks become basins or valleys.

The Basin and Range is formed.

The stretching of the earth, like opening up a book, has revealed astounding geologic marvels for us to see in the Basin and Range.

In fact, the landscape here has been stretched wider by over 100%.

It's the largest chunk of stretched crust on the entire planet.

A striking place to see what this stretching can do is along the border of California and Nevada.

So here we are at the far western end of the Basin and Range Province.

And those are the fantastic Sierra Nevada mountains.

Mount Whitney is one of those peaks out there.

And as you can see, it drops right down into Owens Valley very steeply because the earth is pulling apart right here.

Down on the flanks of the High Sierras, red volcanic cones pop up like blisters here and there.

In fact, volcanoes are everywhere in the Basin and Range, and we'll find out why as we explore.

But the most familiar sight you see in the province is a mountain range, followed by a valley, followed by another mountain range on and on to the horizon, and it's caused by the stretching of the earth's crust.

This geologic process created a world-famous national park in California, Death Valley.

Did you see the sea level sign?

Doug: Here, Basin and Range forces have dropped valleys 280 feet, or 85 meters, below sea level.

So this is it, the lowest point in North America, Badwater, Death Valley.

Doug: The air column above Death Valley is nearly as tall as it gets on the planet, which increases the air pressure and also makes us weigh more than we would on, say, Mount Everest.

The air pressure is so intense here... Doug, voice-over: but the difference is so minuscule that you cannot actually feel it.

OK, so here in Death Valley, this is probably one of the most dramatic examples on earth of the crust of the earth being pulled apart, mountains being thrust up as a result, valleys dropping down even below sea level.

And so the question is, What's causing all this crustal stretching and pulling apart?

And the answer is kind of surprising, and it's a little farther west in California.

So let's go take a look.

To get to the driving force of the Basin and Range topography, I head west.

About 80 miles later, I arrive.

I can't tell you how excited I am to be in this place.

This is probably the most famous geologic feature on the whole planet.

This is the San Andreas Fault.

And, in fact, here on the Carrizo plain in south central California, this is one of the most active parts of the San Andreas Fault.

Cutting a dramatic gash across the land, the San Andreas Fault marks the collision of two major crustal plates in the earth.

Over there is the North American Plate.

Over there is the Pacific Plate.

And the two plates' interactions have almost everything to do with the creation of the Basin and Range Province.

Here, the Pacific Plate is grinding northwest against the North American Plate.

But the Pacific Plate is moving at an angle, pulling outward on the continent while grinding north and west, and that is stretching the Basin and Range sideways and tearing it apart.

Millions of years of movement on the San Andreas Fault has dramatically altered the Basin and Range landscape.

This, in turn, has affected many other things in the Basin and Range, like animals and plants and, in fact, entire ecosystems, and especially water and the way it moves or doesn't in the Basin and Range.

[Thunder] When snow or rain falls, it collects in the basins.

There is no river that leads out of the Basin and Range, so the water pools in the basins and is left to evaporate, and sometimes it dries up.

This is why John Frémont, the 19th-century explorer, called most of the Basin and Range Province by another name, the Great Basin.

In one basin about 25 miles north of Reno, Nevada, you come to a beautiful lake, which is on Tribal lands of this region's original people, the Paiutes.

This is the starkly beautiful Pyramid Lake.

And an interesting thing about this lake is, every time I come here, it's a different color.

You've got shades of blue, medium blue, dark blue.

There's green, there's gray.

It all just depends on the time of day you're here and if there's cloud cover or not.

The water in Pyramid Lake is very clean, very pristine, and it comes from another lake that is also known for its very clear, very pristine waters, and that's Lake Tahoe.

Lake Tahoe is up in the Sierra mountains, which isn't too far from here but many thousands of feet higher, where it catches a lot of rain, snow, and is a very deep lake sitting in a beautiful mountain-rimmed basin.

The water then leaves the lake and comes down the Truckee River.

The Truckee River roars down an amazing canyon.

On one side of it is Route 80.

The other side is the railroad.

Once the Truckee River leaves the Sierra mountains, it meanders across Nevada for a little while before it finally ends up here in Pyramid Lake, where it just evaporates into the sky because this is a closed Basin and Range basin.

And a really cool thing about this lake is it's pretty deep right now, but in the ice ages, ten thousand years ago, it was much deeper than it is now.

We're talking hundreds of feet deeper.

Pyramid Lake is 370 feet deep, about 100 meters, but it was three times deeper during the ice ages, which ended about 10,000 years ago.

At that time, much greater snow and rainfall filled the Basin and Range with so much water that two gigantic lakes connected the valleys.

The western Lake, named Lake Lahontan, was centered on Pyramid Lake.

When the ice ages ended and the climate warmed up, Lake Lahontan shrunk to become Pyramid Lake today.

It would be totally dried up if not for its connection to Lake Tahoe by way of the Truckee River.

How do we know that Pyramid Lake was deeper?

Around the lake, on the sides of the mountains, you can see straight lines that almost look like they were etched with a ruler into the mountains, marching straight up the mountainsides.

And those are actually previous lake levels from when the lake was much deeper than it is today.

And we're talking hundreds, hundreds of feet.

The lakes in the Basin and Range are mostly dried up and encrusted with evaporated white minerals, like calcite, gypsum, and halite, or salt.

Pure salt.

Dry lakes are a place where you can truly get away from it all since nothing lives here.

Well, this is the ultimate in being out in somewhere that's really far from everything, and nothing grows, actually.

It's the middle of a dry lake.

For some strange reason, the sight of a big, wide-open, flat dry lake makes me want to take off running across it.

So I'm just going to put on my running shoes here and a hat that'll stay on while I'm running, and just take off.

See what happens.

[Music] [Music] Whew!

OK.

So, uh... it's pretty cool to think that 10,000 years ago, I'd have to be a fish to do this.

Much further back in time, a giant fish-like creature did live here.

This is a beautiful life-size sculpture of an ichthyosaur, which was an ancient reptile that lived about 225 million years ago in the ocean.

It was the Triassic Period, and the entire Basin and Range was under the ocean.

This creature was living and swimming right here in an ocean.

But now we're at about 7,000 feet elevation in the mountains of central Nevada.

So if that doesn't say something about how active the earth can be, then nothing does.

Ha ha!

Obviously, tremendous geologic changes turned what was once an ocean into the mountainous high desert that is now the Basin and Range Province.

And those geologic forces, driven mainly by action on the San Andreas Fault, as we saw earlier, are still extremely active.

In fact, earthquakes also happen right in the Basin and Range.

And they leave dramatic scars on the landscape.

So I'm walking next to a gigantic earthquake fault, where this side of the hill went up about 30 feet, or 10 meters, in a 7.3 earthquake back in 1954.

So that was a big earthquake, and there were lots of faults coming up all over these mountains here.

Just 20 seconds after that quake struck, a magnitude 6.9 earthquake cut this gash in the Stillwater Range nearby.

[Cows lowing] Nobody was killed during these earthquakes because basically, there are more cows than people living out here, which is why the main road bisecting this area, Route 50, was called "The Loneliest Road in America" by "Life" magazine.

Fiery volcanoes like this often erupted all through the Basin and Range, testaments to the region's restless geologic nature.

None have erupted since the ice ages, so the dormant volcanoes have been eroded to round cones.

The most dramatic place to see dozens of volcanoes bunched together is in California's Mojave National Preserve.

Here, stunning lava flows, once molten but now hardened to black and maroon rock and great fun to climb, oozed many miles from their fiery cauldrons.

This is an amazing lava flow in the Cima Volcanic Field in the Mojave Desert.

This lava came out of that cone right back there.

This is the youngest volcano at Cima.

But even though it looks like it erupted only a few years ago, it actually erupted 15,000 years ago.

A few miles' traverse on a rough dirt road dead ends at a trailhead to another volcano.

This volcano erupted 100,000 years ago.

Its name is Crater J, and because it is in a wilderness area, I had to hike a few hours to get to it.

So here we go.

See you up there.

OK, actually, I've got to get the camera here.

Take that off.

Now we're ready to go to Crater J. OK, see you at Crater J. Bye!

It's well worth the effort to get here.

From the top of the volcano, the views are astounding.

Crater J is very special geologically.

The hardened lava has little chunks of foreign rock embedded in it.

These are called xenoliths, and xenoliths are very rare on the earth.

The xenoliths' chemical makeup has revealed that indeed, the Basin and Range has been stretched apart.

How fortunate we are that this small extinct volcano erupted such important clues about how the Basin and Range formed.

Since the Basin and Range is still stretching and tearing itself apart, new volcanoes could erupt at any time, a sight I'd dearly love to witness.

There are no volcanoes that are active right now in the Basin and Range, but this geyser is the next best thing to a volcano.

Luckily, it's not quite as hot.

This amazing power is being generated because--the pulling apart of the crust is allowing magma to get pretty close to the surface, which is coming in contact with water and creating this amazing geyser.

There was a time long, long ago when the pulling apart and fissuring was so great that all hell literally broke loose in the Basin and Range.

Evidence that this occurred can be seen in the far north of the province.

Heading to the northern part of the Basin and Range in northern Nevada and southern Oregon, the roads get sparser and rougher.

[Pump humming] Another flat tire.

Hmm.

Up here, you see entire mountain ranges that are made of hardened lava flows called flood basalts.

They are a mile thick in places.

Behind me is one amazing lava flow.

Look at that.

That's huge!

These gigantic rocky lumps are the eroded remains of a massive flood basalt in the Santa Rosa Range, just north of Winnemucca, Nevada.

The great floods of lava issued from giant calderas and deep fissures, when the Basin and Range first started tearing apart 16 million to 17 million years ago.

We filmed this extremely rugged landscape with our trusty drone.

[Buzzing] But I let the battery get too low, and it crash-landed somewhere far up a steep brush-covered mountainside.

[Drone buzzing] [Buzzing stops] No roads, no trails, just a vague sense of where the drone landed.

I wanted the drone back, so the search was on.

While searching around, I tried to picture the looming lava shapes being covered with mountain glaciers, as they were during the ice ages.

It probably looked like these glacier-covered mountains we filmed in Antarctica.

Those glaciers slowly but surely sliced up the ancient flood basalts into these fantastical shapes we see today.

I also noticed that the vegetation in this range was distinctly different than in a lot of other Basin and Range ranges.

There are thick groves of aspen trees that I had to plow through, which reminded me of the forests of the Colorado Rocky Mountains.

It turns out this is a Rocky Mountain ecosystem, even though we are hundreds of miles from that range.

But first...

So we're up here looking, and what do you know?

There it is.

Yeah!

Whoo-hoo!

Found the drone.

It was our great luck that the drone still worked, so we could continue filming and exploring the Santa Rosa Range and its peculiar vegetation.

Almost back.

So what about this displaced Rocky Mountain forest, like an island adrift in the Western sky.

So we're right in the heart of the Basin and Range here.

Millions of years ago, the ecosystem from here all the way over to the Rocky Mountains was the same, and then tectonics started acting on that ecosystem.

The land started rifting apart as the Basin and Range began to form.

The ranges lifted up, the basins dropped down.

And on top of those ranges, as they grew higher and higher, their ecosystems became isolated.

In other words, these ancient ecosystems have been stranded in the higher Basin and Range mountains as they pulled apart and became isolated islands, surrounded by seas of sagebrush in the basins below.

There's a wonderful term for these isolated remnant ecosystems, and they're called sky islands.

The highest sky island is the White Mountain Range in California, rising over 14,000 feet, or 4,700 meters.

Here, the Ancient Bristlecone Pine Forest is home to the oldest trees on earth.

One of these trees has been dated at 5,062 years of age, the world record.

But its discoverer, The late dendrochronologist Tom Harlan, has kept secret which one it is.

[Thunder] Probably the most dramatic and beautiful example of a sky island in the Basin and Range is in the Ruby Mountains, near the town of Elko, Nevada.

This is another range bearing signs of being profoundly sculpted by glaciers during the ice ages.

Their idyllic mountain lakes and amphitheater-like settings, the sky island ecosystem here is another remnant of the Colorado Rockies' ecosystem, and all of this is preserved in the Ruby Mountains Wilderness Area and accessed by fabulous mountain trails.

A word about wilderness in the Basin and Range.

It's a fabulous thing, and it allows all these geologic phenomena to be experienced in their true, undisturbed nature by everyone forever into the future.

And it's easy to explore... Whoo!

and to see so many geological wonders here.

Being a desert, the land is generally open.

No real need for trails.

You can just take off walking or climbing.

You come across surprising things when wandering in the desert wilderness.

Wow.

This is amazing.

This is a survey marker done in 1928 by the U.S. General Land Office, which is now the Bureau of Land Management, BLM.

And in 1928, I mean, we're out, way out, in the middle of nowhere, and maybe the surveyor came out here on horseback.

The beauty of wilderness protection is that it preserves geologic wonders like the Kelso Dunes in the Mojave National Preserve in California.

These sand dunes are piled up at the end of a long, windy valley walled in by the Granite Mountains.

The Granites, another wilderness area, are a fabulous jumble of, well, granitic rock!

This type of rock is not that common in the Basin and Range, but it's always easy to spot, always appears in ragged, dramatic fashion, and always beckons me to climb its gritty solid surface.

Amazing view up here.

The sight of a certain type of granite was the magnet that drew gold miners to the Basin and Range in the gold rush days.

Gold and silver forms around granite deep in the ground.

Today, granite outcrops in the Basin and Range rise boldly above the terrain, visited mostly by raptors, perhaps looking to rest their wings.

So come on out in a decent vehicle, bring some camping gear and a lot of water, and experience this wide-open geologic wonderland.

And when you get here, you'll most likely have the landscape all to yourself.

This kind of rock looks to me like it's melting.

It's got all these holes.

And, in fact, this one I can climb into.

See you later.

It's a land with so many faces, so many beautiful geologic wonders to experience and never forget.

♪ ♪