THE GEOLOGY OF PETRIFIED FOREST

The story of the origin of the scenery you see here at Petrified Forest has been patiently pieced together by those who have studied not only the rocks and soils, but the fossil plants and animals contained in them. It is an incomplete story; and so it will remain, though new paragraphs will be added and old ones revised as further research is done.

GEOLOGICAL HISTORY The Forest Lives

Between 180 and 200 million years ago the area that is now Petrified Forest National Park was part of a vast flood plain. At times the streams crossing the plain were wide, raging torrents, at other times they were narrow and sluggish. Small freshwater lakes and swamps, which alternately filled and drained as stream volumes changed, dotted the landscape.

Along the water courses and by the lakes and swamps grew ferns, giant horsetails, clubmosses, and cone bearing trees. Amphibians, lungfishes, and primitive dinosaur-like reptiles lived among the plants and in the waters. Upstream, and on welldrained sites between the watercourses, grew stately pine-like trees which were to become the petrified logs of today.

Throughout the twenty million years of this time period, called the Upper Triassic by geologists, plants and animals lived and died. Most rotted where they fell, but some were buried in mud, sand and volcanic ash carried by the flooding streams. Deep in these stream deposits there was little oxygen, and decay and rot were arrested. Eventually, this material, with the logs encased, hardened into the present day sandstones and shales that make up what is now called the Chinle formation.

The Logs are Petrified

Petrification of once living tissues is a process that is little understood. Apparently, Triassic stream waters here contained chemicals which allowed silica, a mineral in the volcanic ash, to go into solution. This mixture percolated into the wood cells and other water-filled spaces of the buried logs. There the silica was deposited, leaving the wood largely intact. In a few of the logs all of the original wood tissue remains; the silica turned to quartz fills only the cell interiors and holes created before submersion by rot, insects, etc. Most petrified logs, though, have just part of the original wood left in them. Some are almost completely stone.

As Triassic time came to an end, the flood plain with the encased trees sank to below sea level and layers of oceanic sediments were laid down on top of the stream-borne deposits. Mountain building forces later lifted this part of Arizona far above sea level. Entombed in the heaving rock, the trees cracked by stresses imparted to them as the earth moved.

The Logs are Uncovered and Sectioned

In more recent times wind and rain have carved away the deposits covering and surrounding the logs. In level areas the uncovered logs look much as they did when they were buried so long ago. Washed from hillsides, or otherwise disturbed, the broken sections appear to have been cut into regular pieces by some ancient lumberjack, an effect due to the widening of cracks which first appeared while the logs were buried.

PETRIFIED FOREST

Endlessly, cattle and sheep came into the country on the railroad and were turned loose to multiply. At last, they destroyed the grass. Years of drought and overgrazing ravaged the stark beauty of the land. But she is tough, this country. Ageless and resilient. With new conservation measures and the decency of foresighted men, she will come back, strong as ever, for our generation to admire and enjoy.

Crossing the bridge over the Puerco, you drive to several points overlooking the Painted Desert. The land stretches out before you, 44,000 acres of wilderness. Badlands, whipped by wind, baked by sun, lie patient and serene as far as you can see. Delicate shades of blue, mauve, violet magenta, vermillion, red-orange and ochre blend into one another, changing in the clear, dry light.

From Pintado Point above Lithodendron Wash, you can look out over the big empty country. One hundred miles to the northwest are San Francisco Peaks, sacred to the Indians, home of the gods who bring rain. Half that distance away are the Hopi Indian villages high atop the long extensions of Black Mesa. The highest points in the park are Pilot Rock and Chinde Mesa. Behind them lies the sprawling Navajo Reservation. The Navajos say that the pieces of petrified wood are the broken bones of Yeitso, giant monster killed by the war god, Slayer of Enemies. One hundred miles to the south, the White Mountains rise blue and clear-cut from the plains. They are the home of the Apaches, once proud warriors, now proud cattlemen. From vantage points along the rim of the Painted Desert, lawmen of frontier days watched for signs of campfire smoke. In those days, the badlands were known as "Robbers Roost." Gene Eagles, who remembers the unstable early days, wrote: "Into the hundreds of trailways among the buttes, bandits would flee after a holdup of stagecoach or pony express rider. Tracking their unshod horses on the barren, hard clays was next to impossible, except for a Navajo Indian. And the Navajos of those days were not on speaking terms with the lawmen. Indeed, most of these preferred being friendly with the bandits rather than the officers, for reasons which seemed ample to the Indians. It suffices to say that the chances of capture were extremely remote unless the pursued became over-confident and careless about campfire smoke. The pursuit of the bad guys by the good guys continues. In 1966, 60,250 pounds of wool were involved in theft attempts. The average theft was two pounds. Three hundred thirty-one theft incidents occurred. Eleven and one-tenth per cent of vehicles entering the park attempt to take wood away. Law enforcement forcement rangers patrol the grounds and check cars at the gates in an attempt to preserve serve the forest. If everyone took away just a small chip for a souvenir, in one generation the wood that took 200 million years to form would be gone and one of our most priceless national treasures would be lost forever. Petrified wood from private lands is available at curio shops all over Northern Arizona.

The time is past when we can be proud to fight the elements only for our own private ambitions. The land belongs to all of us. As stewards, we must reverence it, respect it, and nurture it in whatever capacity we can. Above all, we must enjoy it for our brief life on earth. The earth remains timeless, patient, ever-changing, re-creating. The earth was here long before we were slimy creatures crawling sluggishly over the mud of ancient swamps. It will be here when we are gone.