(David) The Colorado Plateau is internationally famous for its geological wonders.

But for thousands of years, myriad native peoples have also called it home.

(Announcer) Funding for In the Americas with David Yetman was provided by Robert and Carol Dorsey Additional funding for In the Americas with David Yetman was provided by Laura and Arch Brown and by the Guilford Fund.

(David) The Colorado Plateau is home to tens of thousands of archeological sites and a variety of peoples who occupied them.

The habitats also range greatly from forested highlands to grasslands to scorched middle lands like deserts.

The people who lived there were resourceful and learned to deal with the environment and the resources available to them in a variety of ways, which made them endure over thousands of years.

The Highlands near Flagstaff in northern Arizona, are heavily forested.

Nearby Walnut Canyon cuts a deep trough into the plateau.

Ancient peoples found it provided shelter and abundant water.

The people who lived in Walnut Canyon had experienced advantages and disadvantages.

The advantages were natural caves that occur in the combat limestone, where water can actually carve out over the eons.

Small caves undercuts like this.

There was a lot of games.

There were many, many different plants that they could harvest.

But the limit of agricultural land where they could raise their corn and other crops was limited.

And the growing season was very short.

We are almost 7000 feet in this area.

This means that winters come early, springs come late Up on the rim, they have Pinyon pines, which are a great source of nuts.

Archeologists call the people who lived in Walnut Canyon and other places Sinagua, which in Spanish means without water.

And we can see that in a heavy rainstorm and they can get really heavy here, particularly summertime.

This would have been a great gathering place.

They wouldn't get wet and the rock does maintain heat.

So it was a harsh climate.

It was made easier by the great mass of rock that held the heat and protected them from the wind.

The Kaibab limestone is the highest rim, the top layer of the Grand Canyon, and covers a lot of the Coconino Plateau.

It's very hard rock, but it's porous and water seeps through it.

The formation of the caves was limited to the place where the Kaibab limestone meets the Coconino Sandstone below.

There was a reason for making this entrance somewhat constricted and I'm sure in the wintertime it kept heat from flowing out and cold air from coming in.

One of the big advantages to people living in the Highlands and the Coconino Plateau was the abundance of game.

There were elk, bighorn, deer and antelope, all within a space of 25 miles or so.

And although you had to be a pretty skillful hunter, they knew how to.

And so their diet probably consisted of a lot more animal protein than those who lived in the grasslands or in the hot desert.

So they managed for a couple of hundred years to develop a sustained community.

And then come the 14th century or so, they as so many other peoples, moved from the Colorado Plateau.

Because of a number of factors, probably the great droughts.

The people of Walnut Canyon have distant relatives who lived about 30 miles to the north on the arid plains.

Their settlements are now included in Wupatki National monument.

This is the archeological site called Wupatki, now a national monument of the National Park Service.

It was populated this area, at least by probably up to 2000 people about a thousand years ago.

Look out and we see dry, rocky mesas, volcanic hillsides.

We see small valleys that are dry.

I wonder how could they raise a crop here?

Well, they did, but it was not always a small town.

After Sunset Crater erupted in 1085 or thereabouts, people around that area found that they could not continue to farm.

So many of them moved here.

But by the middle of the 12th century, the place was abandoned.

The stone from which the buildings are constructed here is Moenkopi sandstone.

It's a layer of actually the Colorado Plateau, but can be cut and shaped into brick like pieces, which is ideal for building a little bit of mortar.

But you have to have beams to hold together the various stories.

And those beams came from the forest near the San Francisco peaks, at least thirty miles to the north, all carried by hand.

No domestic animals here.

Now, as we look around, you wonder how it could ever have been possible.

The Sinagua people developed here in sites the South, while the Anasazi or your ancestral pueblo people were best known for their sites to the north and east.

Perhaps descendants of today's Hopis and Zunis.

They lived here for a couple of hundred years and had connections all over the Southwest, some of them even as far south as Mexico.

When it was fully inhabited, the Wupatki Pueblo probably had up to 300 people living in 100 rooms that amounted to a lot of food, a lot of grinding of corn on grindstones.

The site had great views.

It was a place where they could easily communicate with other sites and they are scattered all over.

Scattered around this area and the Colorado Plateau are tens of thousands of abandoned buildings.

For two to three thousand years, Native Americans had been building sophisticated buildings.

And farther to the south, civilizations, enormous achievements, both social and structural.

There are a number of theories as to why Wupatki was abandoned in about 1225.

One of them has to be that they ran out of wood, firewood and perhaps wood for construction.

If you have a couple of thousand people needing to have fires for warmth and cooking every day of the year, soon you're going to run out of firewood.

And cooking is vital to people who live in these kind of multifamily areas.

Exhaustion of resources had to play a factor in the abandonment of Wupatki in about 1225 A.D., when early archeologists began excavating Wupatki, they thought that this structure might be a great kiva, a ceremonial structure that often was underground.

But the more they studied it, they found none of the trappings of a kiva.

So they have concluded today that it was just a very nice community space in an area that's hilly and very steep and lacking in places where people can get together.

And that was the plaza of Wupatki.

This structure, which has been painstakingly reconstructed by archeologists, is a ball court.

Ball courts were know very well from Mesoamerica, but not well known this far north.

It's a very unusual structure.

It was for games.

We don't know what kind.

Wukoki Pueblo is about five miles from Wupatki.

It's much smaller and had fewer people living here.

But the builders at Wupatki must have learned building that building and come here and used their immense talents to make the loveliest structure in perhaps all of northern Arizona.

An hour's drive to the east brings us to a stark desert landscape now part of Petrified Forest National Park.

It's an arid landscape full of startling revelations.

The Triassic logs of Petrified Wood are one example, the painted desert is another.

Another yet, is the recorded presence of ancient peoples and their unusual homes.

This top layer gives us a surface very good for receiving desert varnish over thousands of years.

And native peoples found this the ideal place to peck away at that varnish and leave their complicated designs.

The Park Service calls this newspaper rock, and it's a good idea.

There could be messages left carved into desert varnish on these boulders, but it's probably something that had greater long term interest that a mere newspaper.

These were places where people could leave messages and could communicate spiritual or even political ideas engraved into the desert varnish on these very resistant rocks.

The Chinle formation, this striped strata that we see from here falls away, dissolves.

But on top is a layer where all the petrified wood is.

As the Chinle erodes, hundreds or thousands of lives roll out downward of that bottom.

And here we see tens of thousands of pieces of logs that were trees and are now stone.

This is the classic view of the Chinle formation.

It's what's neat is at the very top of the Chinle, like everywhere in northern Arizona, southeastern Utah, northern New Mexico, you have the same Chinle everywhere covered by thousands of feet of other rock.

But here at the very top, the Chinle has this tough formation that holds on to the logs, and it prevents this clay stuff, which is the lower stuff from washing away.

If it were not for that tough layer, we wouldn't have the Petrified Forest.

And so it holds on.

And gradually this clay like stuff, it's bentonite clay, which when a water hits, it just expands like crazy.

The logs then tumble down onto that and we get to see them.

And all these little pebbles here are actually rocks that came down from much higher and younger rocks elsewhere brought down by rivers along with the logs.

And if we look at each one of them, some of these are from formations that are a billion years old.

Some of them would be only 200 million years old.

Where do these different shades or pastel colors come from?

Well, as the volcanoes to the south and west exploded over a million or 10 million, 20 million years, each blast of ash had a slightly different composition with minerals inside it.

And the metals in those minerals produce a different color when they meet water, when they meet other chemicals.

And so we get this these stripes of different colors found only in a place like the Painted Desert.

There are almost no plants and they can't grow there because the ash from the volcanoes over the millions of years forms this clay.

It's called bentonite that when water hits it, it expands up to eight times its volume, just like that.

And then when it dries out, it contracts and cracks.

Well, plants don't stand a chance.

So we have these clearly eroded cliffs everywhere with one plant, every 50 acres.

If we were to come back to this very place in ten or 20 years, all of these rocks would have moved somehow, a little bit, maybe a lot.

Gravity keeps pulling them down, and as long as there's not something holding them, gravity will take them away.

And when you add a water from a flashflood to that, they will go flying.

There aren't a lot of big hills.

There are mesas.

But if we come up in the southern part, we find a small hill.

And on top of that is what is called the Agate House.

It is constructed entirely of petrified wood blocks with a little mortar all holding on together.

This actually was a pre-Columbian site, perhaps ancestral Pueblo.

People living here building their house out of petrified wood.

At the time when they first reconstructed this back in the 1930.

The best they knew how to.

It was believed this was the only dwelling made out of petrified wood.

The Park Service and other archeologists have found many other sites that are built of the Petrified Wood, and it is such fine stuff Nowadays, contemporary archeologists cringe when they see how this was reconstructed because it was probably quite different.

I suspect that the pre-Columbians who built this selected some of the prettiest pieces with the Opaline type quartz.

And I suspect there were bragging rights among the people who built this and maybe who lived here, that we have the prettiest house in all of the Colorado Plateau or whatever they called it.

Any people who had the aesthetic sensitivity that we know those people had would have marveled as the colors changed, as the sun moved across it.

It's really hard to date the petrified wood, except for the area where it comes from.

We know that petrified wood is probably 225 million years old.

Oh, my.

The color.

The petrified wood found in this area is the finest in terms of color in the world.

There are dozens and dozens of sites in the world where you find petrified wood, but only that from northern Arizona, from this region has the colors, the reds, the oranges, the purples, even the blues, combined with the pale color of the quartz and the opaline textures.

Nowhere else has that, and experts can instantly look at a piece of petrified wood and tell where it's from and if it's from here.

Of all the archeological sites in the United States, Chaco Canyon is the most studied, the most complex, and the most intriguing.

Its ancient history is still being unraveled and disputed.

At the upstream end of Chaco Canyon is Fajada Butte.

It is perhaps the most significant landmark for the immediate Chaco region.

It is also the object of intense interest to astronomers as well as archeologists.

A place where only one day of the year on the spring solstice, an image would be cast that looked like a dagger on a wall where sunlight passed through.

Many people now like to follow the Chacoans interest in astronomy and see their astonishing, accomplishments at predicting the seasons, where the moon lies, where the sun lies on any given day.

Pueblo Bonito in Chaco Canyon is what makes Chaco Canyon the most important archeological site in the United States.

It has several hundred rooms.

It has many circular structures that a lot of archeologists call kivas.

It was several stories high.

It was an immense structure and at its height, built to precise measurements unlike anywhere else at that time.

Pueblo Bonito is famous for its "D" structure, like the letter D, the meaning of the D and why it became so popular is widely debated among archeologists.

But one thing is certain that the straight edge forms a lineament, forms a North-South boundary with great precision, and the others have the same important relation to that alignment that very straight line heading in a certain direction.

The builders who were in charge of the last and finest refined building, the outer skin of Pueblo Bonito, knew what they were doing.

They had the science of making a straight wall with very little mortar included.

They had that down to a inheritable science.

They were perfect at it.

Here we have a wall that's a thousand years old that is bulging only in a few places.

In some places later restorers have added mortar.

But for the most part, that's how it was.

If we come down here and look at the outer wall, the straight side of the D, then we have to marvel at how they were able to construct something that long that straight, that has endured for a thousand years.

The people who lived at Pueblo Bonito were not on the same social level as the people who lived in the smaller type of structures found throughout the region.

They were elite.

They were wealthy.

They were much better fed than other people.

We are now going to get to go inside some of the rooms which the Park Service has generously left available to us.

They weren't real tall.

It's neat to see how they put a lintel of wood over a window.

So I'm going to crawl through through this building complex.

They certainly were not as tall as people tend to be nowadays, but we can see the height of the ceiling here.

These pine trees brought in from great distance in this room we█re lucky to be able to see how we have three stories.

I'm not sure I'd want to live on that top story because maybe the termites could get into the pine, but it seemed to have lasted for a long, long time.

Throughout the complex here at Pueblo Bonito, we see signs of early, middle and late architecture.

They're distinctly different.

And the late style with the perfection they have found in laying the rock and laying out the angles and laying out the sides perfectly straight.

That is a treasure, international treasure of human achievement in building.

So this could have been a semipublic space in here to allow people to get access to their private dwellings.

We have to remember that not a lot of people lived here, but there was plenty of space for those fortunate few that did live here.

Many archeologists classify these round structures as kivas, which tie them into a very important part of Pueblo community as far as ritualistic, sacred and communal properties.

Other archeologists are skeptical of that and believe that each family of the small number of families that lived here, these elitist families, had one of these.

Every four or five rooms.

You find one of these circular structures.

Maybe they use them for spiritual communal things, or maybe for having fun or for storing things With the use of carbon-14 analysis, and tree ring dating experts in the field are not only able to tell when these beams were cut, but from where they were cut because each area has its own very subtle chemical trace.

And so they can tell you what mountains each of these beams came from.

It required some pretty top heavy administration to organize, bringing 200,000 pine trees across that very rugged land to build one huge house or five huge great houses.

As we look at archeological sites in the United States, places like Mesa Verde with their miraculous cliff dwellings, Montezuma's Castle, even such places as Wupatki, none of them can compare with Chaco Canyon for the amount of research, the amount of discussion and the amount of interest internationally.

The Chaco Canyon has raised among professional archeologists.

Some people still call it an enigma.

Some people call it a mystery.

Other people call it a place that is gradually revealing its so-called secrets and is of unending interest to archeologists who still come here to talk about this, the most important archeological site in the United States.

Join us next time in the Americas with me David Yetman.

Northwest New Mexico has no large cities, just the Colorado Plateau with its vast spaces and scant population.

Ancient peoples left their mark near the Rio Grande and many of their descendants make their homes among the wonders of the earth.

Gigantic Cabezon, El Mal Pais Lava field, Shiprock and the rock sculptures of the Bisti Badlands.

It is estimated that 200,000 pine trees were incorporated into the structures in this canyon.

Where do those pine trees come from?

They came from the Cusco mountains, 40 to 50 miles to the west.

And imagining the amount of labor that was required to move those suggests that the amount of work to build Quetzalcoatl, to build Pueblo Bonito to build Pueblo del Arroyo was incalculable.

Funding for In the Americas with David Yetman was provided by Robert and Carol Dorsey Additional funding for In the Americas with David Yetman was provided by Laura and Arch Brown and by the Guilford Fund.