RAINBOWS IN AGATE FROM AN ANCIENT FOREST

In scattered locations throughout the vast semi-arid parts of Northeastern Arizona lie the cracked and broken remains of once proud forest trees of an ancient time. Countless battered tree trunks which, through millenniums of time and the patient work of nature, have been transformed from hulks of ordinary wood into logs of colorful agate, banded, mottled and marked by mineral stains to form combinations of colors rivaling those of any rainbow. Forest giants which never felt the bite of a woodsman's axe nor heard the songs of birds in their branches now receive the exclamations and admiration of man and evoke countless questions about their origin and the unusual transformation through which they have passed. Some questions are asked for which man does not have and may never have the answers. For, after all, man is but a recent addition on this ancient earth. What manner of trees were these? Where did they grow, and how did they "turn to stone"? These and many other questions are asked about them. Unfortunately to many people of this enlightened age a tree is just a tree. To the trained eye of the botanist each family, genus, and species of tree has its own distinct characteristics that separate it from all others. To the eye of an expert technologist the wood structure itself differs in each family of tree enabling him to identify a species from a sample of wood alone. So turning the pages backward from the present to the past the chain of relationships can often be traced back into early time. Today, in the tropical sections of South America, in Australia and the islands of the South Pacific are found The photograph on the opposite page is a study of the Balanced Log in the Rainbow Forest of Petrified Forest by Josef Muench. A living tree some 160 million years ago, this section is now semi-precious stone. The following double page panel is from a photograph by Fred H. Ragsdale. Here is shown the magnificence of Petrified Forest in all its color.

Agate Bridge is probably the most famous petrified tree in all the world. One hundred eleven feet of it are exposed.

Several species of Araucarian Pines, relatives of our own pines of this country, but quite a bit different from them. Several of these have been imported into the United States for use as ornamental trees, the two best known being the "Monkey Puzzle Pine" and the Norfolk Island Pine. Only yesterday, geologically speaking, but in our reckoning of time about 160 to 170 million years ago, during the Triassic Period of geological time, an earlier form of Araucarian pine grew in this part of North America, a relative of the modern types. A tree, comparable to many of our present forest trees in size, attained a diameter of eight feet or more and some of them exceeded two hundred feet in height. At least two other species of trees, Woodworthia and Schilderia, grew along with these pines but apparently in much smaller numbers. They, too, were primitive trees, smaller in size than their Araucarian neighbors. These ancient forests grew on high ground through COLOR DATA The photograph on the opposite page is by Hubert A. Lowman. Weird striations of blue, gray and violet give the name of Blue Forest to this portion of Petrified Forest National Monument. This badlands material here is called bentonite, a form of decomposed volcanic ash. After a rain, the colors of the formation stand out in dazzling brilliance. which numerous streams flowed. Streams which eventually wound their way out into an extensive flood plain, a country low, flat, and swampy, very different from the Northeastern Arizona we are familiar with today. A plain covered by verdant growths of ferns, scouring rushes, and cycads, with mud flats across which large web-footed crocodilelike reptiles, the Phytosaurs, splashed and through the mire wallowed primitive amphibians, the Stegocephalians, a heavy, flattened, short-legged, 500-pound relative of our modern salamanders. The forest trees died from various causes or were uprooted by the rushing streams and in the course of time many of the tree trunks were carried downstream by the torrents, gouged, battered and broken during their rough journey. Finally they floated out into the lower country where they became stranded on bars or collected on the bottom of the waterways and lakes, perhaps 50 to 100 miles from their point of origin. With these battered logs came quantities of sediments; mud, sand, volcanic ash and other materials which were spread out layer after layer around and over the logs as the streams shifted their flow back and forth. In the course of time this deposit accumulated to a depth of 400 feet or more. It is now known as the Chinle Formation. During the time this deposition was slowly taking place, The land mass over this part of the continent was gradually subsiding. It continued to settle as layers of other deposits were washed in and left on top of the previous ones and finally the region was covered by a long arm of the sea. About 60 million years ago, at the close of the Cretaceous time, the uplift of our great Rocky Mountain system commenced, a gradual rising movement that has continued nearly to the present time. The basin in which this collection of buried logs lay rose with it. This uplift brought with it the activity of erosion which has continued through the ages until almost all of the upper layers of material have been washed away and the many tree trunks, once buried deeply, have been exposed on the surface, but now as hard, colorful stone. As this erosion continues during future centuries more and more of this petrified wood will be uncovered. How were these ancient trees petrified? The most generally accepted theory of petrifaction is that of the infiltration of mineral-laden water into the wood. The wood must be buried in a deposit containing a large amount of mineral which can be picked up by the ground water.The cellulose and lignin that formed the cell tissue of the wood remained to serve as a framework while the min-eral was gradually deposited in the cells until all of the spaces were filled in forming the petrified wood.

Although petrified wood is found in hundreds of deposits throughout the world, some of which were preserved by other minerals, the most common agent of petrifaction is silica. In this case the silica was deposited in an agatized noncrystalline form. The normal color of silica without mineral stain is white or gray. Sometimes small amounts of other minerals were in the solution with the silica, or were brought in as a secondary deposit in cracks, checks, or other openings in the petrified or partially petrified wood. Iron oxides in small quantities produced the great variety of shades of red, brown and yellow. Black color is usually due to manganese or carbon. Thus the combination of minerals produced a rainbow of colors in the agatized wood.

One of the most noticeable features in the petrified forest today is the fact that these petrified tree trunks are cracked and broken into sections. Many of them look like they have been sawed by man. This fracturing is believed to have been done after the wood was petrified and during the period of uplift of the region. This was brought about by the effect of earth vibrations and pressure on the buried, brittle logs, filling them with fine cracks which became larger when the logs settled and after they were exposed by erosion. Thus the petrified forest scene today is composed of many broken sections of the petrified logs scattered over the landscape with here and there long logs more recently uncovered by the forces of erosion and still intact. This erosion and weathering action is still continuing during the passing of time. Petrified Forest National Monument was established to preservefor the future the largest concentrations of this petrified wood. It can be preserved only by careful observance, on the part of the visitors, of the regulation prohibiting its removal from the monument. For visitors come by hundreds of thousands annually and the supply of the petrified wood is not as inexhaustible as it may appear. Petrified wood is found in many scattered locations outside of the monument boundaries and all of the wood sold commercially is obtained from these private sources.

There are six major areas, within the monument, where extensive concentrations of petrified wood have been exposed by erosion. The Rainbow Forest, First, Second, Third, and Blue Forests are located at various points along the monument highway route and may be reached by road and trail. Each contains various features of interest. The Black Forest, which is not yet accessible to visitors, lies in the northern part of the monument and is enclosed by a portion of the Painted Desert. All of the monument is really a part of the Painted Desert badlands although the southern portion is separated from the rest by a narrow strip of land not yet eroded away.

This famous Painted Desert forms a long curving border to the Navajo Indian Reservation, a border extending from near the New Mexico line westward to the Colorado River near the Grand Canyon. It is a colorful, often fantastically eroded badlands of bentonitic beds stained with shades of red, orange, yellow, blue, purple and brown by iron and other minerals. Arid or semi-arid with only a sparse vegetative cover, these soft beds are subject to rapid erosion during Arizona's season of torrential rains, occasionally exposing more deposits of petrified wood.

Today these ancient trees, now glittering jewels of the desert, the Petrified Forest, lie in their picturesque surroundings, an example of the intricate and devious ways of nature and an inspiration and encouragement to man to learn more about and appreciate the works of the infinite hand of God.