Natural History

The Painted Desert An Antique Land the Gods Forgot

All morning I've wandered among eroded cones, slumped cliffs, and rain-slashed gullies north of Kachina Point in the Painted Desert, where lie the bones of the huge beasts of the Triassic period and ancient wood turned to stone. Six one-liter plastic water bottles strung from strap rings on my already stuffed backpack glint in the sun like crystal baubles.

But the weight across my shoulders feels more like bricks than crystal baubles, so I've stopped to rest beside a wide desert arroyo, Lithodendron "stone tree" Wash, named by Amiel Weeks Whipple who led a survey party through this territory in 1853 and was astonished to see so much wood turned to stone.

Strewn about are the remains of petrified trees: thumbnail-size chips, slabs with edges so precise they appear microsurgically cleft, and substantial logs several feet long and up to 12 feet in circumference. I kick the end of a log jutting from the ground, testing its balance. It doesn't budge. I sit down.

Formed by a process in which water-borne minerals replace most of the natural wood fibers, petrified wood is dense stuff. I'd guess the exposed portion of the log I'm sitting on, perhaps a little more than a cubic foot, weighs about 170 pounds, my body weight. I pry a smaller chunk from the red clay in the wash bank and try to wipe it clean. Even when dry, ocher clay smears my fingers, and lumps of the stuff, wet and sticky from recent rains, gum up my boot treads. The red clay, bentonite, is used as filler in chewing gum and adhesives.

The hunk of petrified wood, irregularly shaped, is no bigger than a good-size russet potato, yet has the heft of a 16-pound hammer. Tiny crystals on the surface flare then dim as I rotate them from light to shade, producing a kaleidoscopic range of muted colors white, gray, yellow, orange, rust, red, blue, purple, black and random patterns, no two appearing twice in sequence.

Peering at this amorphous chunk of wood-turned-agate, I grapple with the notion of its antiquity. Ancient, antediluvian, archaic, prehistoric, primeval words fail. More than 225 million years old not that long in the slow pulse of geologic time, but its age is a span my imagination cannot fathom, no more than it can wrap itself around the time and distance of a light-year.

These pieces of stone wood and this strange, shifting, polychromatic terrain I'm tramping across, its bizarre geometry still eroded by water and wind, aridity, and time, have for thousands of years inspired wonder in those who pass through.

Navajo mythology teaches that petrified logs are the bones of a giant monster, Yietso, killed by the tribe's ancestors. I'm too wise to believe that, I think, yet allmorning I sense an odd kind of displacement, deeper than that felt in merely unfamiliar terrain. I'm not lost; I know that, but there's a disorienting, surreal quality about this place. I'm ready to believe anything.

No birds sang from its branches when the tree fragment in my hand, a primitive conifer, grew upslope from tropical rivers and lakes 225 million years ago. It was during the Triassic period, the dawn of the age of dinosaurs when many trees attained heights up to 250 feet, towering above ferns and horse-tails that were themselves giants by modern standards.

And when it finally came along 50 million to 75 million years later, the first bird, the archaeopteryx, a reptilian creature with wings, a long tail, and a beak full of teeth, was more like a nightmare that lurks at the edge of our collective unconscious than the feathery sprites that now brighten our lives.

But before modern birds evolved, plants set the stage. The tree fragment I'm holding and other plants of the Triassic propagated by releasing pollens upon the winds. Chancy at best, but a method still used by pine trees. In time, though, birds and insects became sexual go-betweens for plants, making reproduction less haphazard.

Then came flowers. A dazzling array of colorful, multiform blossoms, attractively aromatic and tasty. Flowers with sweet nectars and succulent fruit that would at once attract birds to do their sexual bidding and ultimately reciprocate by providing the high-energy sustenance that changed birds into feathered dynamos. But these true flowers (and grasses), able to nourish and protect their offspring within a seedcase called an angiosperm, were not to become common for more than 100 million years.

So the Triassic, the time from which our slump of stone wood is a detail in the fossil record, was a period of gigantism. The dominant animals were amphibians and reptiles. Picture an amphibious creature eight feet long with a large, flat head and rows of needlelike teeth. Hideous? Yes. But dreadful as it may sound, the metoposaurus, the largest amphibian of the period, had legs too puny for much terrestrial locomotion. And, no matter how numerous, its small, pointy teeth weren't much good for chewing anything but fish. The large amphibians probably were easy prey for the rutiodon, one of the larger Triassic reptiles. A true monster, 30 feet long, its body was covered with bony armor plating. With powerful jaws and large flesh-rending teeth, the rutiodon was quite crocodilian though not an ancestor of modern crocodiles.

Even more fearsome was an upland predator, the postosuchus. Twenty feet long, it had strong hind legs and may have been capable of short, bipedal sprints. In fact, some reptiles of the Triassic period seem very much like the large lizard-hipped, bipedal dinosaurs that came along millions of years later during Jurassic and Cretaceous times. But they are unrelated.

The coelophysis, one of the earliest dinosaurs, however, did appear during the Triassic and, oddly enough, it is one we know most about. For most of us the word "dinosaur" (fearful lizard) stirs an image of the 75-ton brachiosaurus, or the 90-foot diplodocus, creatures for which even "behemoth" seems an inadequate descriptive term. But the early-arriving coelophysis, weighing only 70 pounds or so, was built more along the lines of an eight-foot-long greyhound. What it lacked in bulk, however, it made up in ferocity. Supple and quick, it preyed on small lizards, maybe even insects, ripping its victims apart with sharp birdlike claws and slicing them with serrated teeth into chewable bits.

Towering trees, monstrous reptiles, huge fish-eating amphibians all lived upon the Earth's single Triassic supercontinent, Pangaea. The arid, sparsely vegetated tableland we call the Painted Desert was then close to the equator.

Its sea-level climate was warm and wet, and its streams and rivers teeming with colonies of clams and mollusks and vast schools of fish meandered northwest through lush flora into marshes and ponds. Although experts disagree, the essentially tropical climate may have been beset by periods of drought, and severe storms likely lashed the land, destroying vast tracts of forest.

Whether killed by old age, storm, or some other calamity, the tree whose remnant now lies between my feet among bits of orange peel fell among giants of its own species and began slowly to decay. Scores of trees, our tree among them, tumbled into slow-moving rivers to float downstream into swamps. Perhaps from grinding against the corpses of other trees in logjams where waters converged, its branches were sheared off and its bark scraped clean before it sank into its swampy grave.

Over time, our tree, along with the decomposing carcasses of other Triassic forest giants, was buried by layers of silt and mud. Cut off from oxygen and sunlight by this thickening mantle, the tree's decomposition slowed and then stopped.

On land, other processes were going on that would gradually turn our tree to stone. Set adrift by powerful volcanic eruptions, great plumes of ash clouded the Earth's atmosphere. Broadcast over a wide region, silica in the ash settled to Earth, much of it into the marshes and swamps, where it combined with water and air. Over eons this silica solution seeped through hundreds of feet of sediments infiltrating the logs buried deep within Triassic muds and clays.

The metoposaurus had legs too small for fleetness on land, but its long tail was ideal for swimming. The amphibian probably spent most of its time around ponds and streams and in marsh areas looking for food.

Gradually, the silica in the solution encased the trees' own cells in quartz crystals. In those places where boring insects or decay had made holes in the wood, larger crystals formed, some of them semiprecious gems such as amethyst and smoky quartz. And the substances permeating these stone-wood fossils and the layers of mud and shale that comprise the Painted Desert brought shades from Nature's palette that gave this place its name: yellow, red, and rust from iron, blue and blue-green from manganese, black from carbon, white and gray from quartz.

Meanwhile, cataclysmic forces changed the Earth's geology and climate in ways that would gradually resurrect our tree and thousands of other Triassic forest denizens from their long burial. Continental separation occurred: North and South America and Africa drifted away, breaking up Pangaea; ocean basins opened. And, the climate of the Painted Desert region began to dry out. Crushed by the weight of overlying rocks, the buried trees began to crack into pieces, a process accelerated by upthrusting, tilting, and fracturing of the Earth's crust.

Slowly, inexorable forces began to shape the terrain into something resembling the Painted Desert today. Black lava, which had lain like a blanket over the region for ages, gradually wore away, exposing the soft rock beneath. Finegrained mudstones, claystones, siltstones, and coarser sandstones crumbled, eroding easily in wind and rain, and the layers of sediments covering the petrified wood began to wash away. Cycles of sun, wind, and rain repeated over time - finally exposed segments of petrified log, leaf imprints and other plant remains, and the fossils of Triassic animals entombed for millions of years.

The process continues. Daily, new fossils quite literally emerge from eroded terrain in the Painted Desert. The elements are relentless. Winds up to 85 miles per hour have been clocked here, hurling particles at a velocity that sandblasts the rocks, removing layers that reveal to paleontologists more of the Triassic past.

I've just driven 10 miles on a washboard road across bleak Navajo country tablelands to a small sign that announces "Grand Falls Viewpoint." I'm astonished at what I see beyond the promontory I stand on. Dark brown water roars over a series of falls and plunges 185 feet into a deep gorge. A sickly yellowish mist rises from the boiling churn at the bottom andis quickly dispersed by a stout breeze. This is the Grand Falls of the Little Colorado River about midway between Holbrook and Cameron. The river valley, running northwest between Holbrook and the Grand Canyon, essentially defines the territory encompassed by the Painted Desert. Lithodendron Wash all the gullies and washes I've hiked across out in the Painted Desert drain into the Little Colorado.

The Painted Desert

A sterile environment with few plants to hold its soils, the Painted Desert is vanishing: in 10 years as much as 2.5 inches of soil erodes from its steeper slopes; the rate at which the sandstone cliffs are disappearing hasn't been measured.

Suspended in the thick, chocolate cascade before me, sweeping downstream to the Colorado River, are the shales and clays of the Painted Desert. In time these heavy silts, backed up behind mighty dams, will fill Lake Powell and Lake Mead. Slowly, yes. But as inexorably as those earlier sediments filled the lakes and ponds of the Triassic. Ages and ages from now, the Painted Desert itself will be gone, swept away to the Sea of Cortes.

Desert Images: For more about the Southwestern deserts, we recommend Eternal Desert, a dramatic book that captures the mystery and beauty of the desert in 114 photographs by premier photographer David Muench, with an essay by historian Frank Waters. To place an order, telephone toll-free 1 (800) 543-5432. In the Phoenix area, call 258-1000.

WHEN YOU GO

Getting there: Access to the Painted Desert may be gained along State Route 89 north of Flagstaff or Interstate Route 40 east of Flagstaff. The Petrified Forest National Park near Holbrook and the Wupatki National Monument north of Flagstaff offer printed information. (Exhibits of many of the plant and animal fossils from the Painted Desert can be seen at the Petrified Forest National Park's visitors centers.) To travel to Grand Falls, take Camp Townsend-Winona Road east from State 89 near Flagstaff approximately 8 miles to Leupp Road. Turn left and travel east-northeast on Leupp Road approximately 10 miles to Navajo Route 70. Turn left and continue north about 10 miles to Grand Falls. A sign near the Leupp Road-Navajo Route 70 intersection says: "Grand Falls Bible Church, 1 mile."

Temperatures in the Painted Desert are extreme in summer. Travelers should always carry extra water, sunscreen, and wide-brimmed hats for protection. Water flows at Grand Falls only during spring snowmelts and the summer rainy season.

Nearby attractions: Other area attractions include the Museum of Northern Arizona in Flagstaff, Walnut Canyon National Monument, Sunset Crater Volcano National Monument, and the San Francisco Peaks.

Accommodations: Motels and restaurants are available in Flagstaff, Cameron, Winslow, and Holbrook.