Dinosaur National Monument is the legacy of rivers, past and present. Here, preserved in the sands of an ancient river, is a time capsule from the world of dinosaurs the fossil bone deposit that gives the park its name. The Dinosaur Quarry has revealed many secrets of the past, but the remote and rugged land around it, created by today s rivers, is a secret of the present, known to few travelers.
Stand on the tip of Harpers Corner and look down at the rivers far below; your gaze is spanning time as well as space. In the rocks beneath you are fossils of sea creatures two or three times older than the dinosaurs. Upheavals that began about the time that the last dinosaur died jolted these shells far above sea level and downward cutting rivers stranded them on this promontory in the sky.
Seen in this context, the Age of Dinosaurs is but a brief chapter in a long story, and only a paragraph about the dinosaurs themselves is written in the rocks here. Not until about the midpoint of dinosaur history, about 145 million years ago, did a suitable habitat develop here-a low-lying plain crossed by several large rivers and many intermittent-streams, clad in a variety of ferns, cycads, clubmosses, and clumps of tall conifers. This was home to dinosaurs such as Apatosaurus (better known as Brontosaurus), Diplodocus, Stegosaurus, and other vegetarians, and to the sharp-toothed carnivores-Allosaurus was the largest at this time- that preyed upon them. As these animals lived and died, most of their skeletons decayed without a trace, but in at least one spot, river flood-waters washed a great number of carcasses and bones onto a sandbar. There, mixed with the remains of turtles, crocodiles, and clams that lived in the river, the bones were preserved in the sand. This layer itself was not very thick, but thousands more meters of sediments piled up on top of it as the sea crept in and out during the last part of dinosaur times. Dissolved silica percolating through the strata turned the ancient river-bed into a hard sandstone and mineralized the bones buried within it.
When the Rocky Mountains began to rise to the east, this area went along for the ride. Here, the mountain-building did not push up the rock layers from below, but instead it squeezed them from the sides, warping and tilting them, sometimes cracking and shifting them along fault lines. Rain, frost, wind, and gravity slowly but steadily wore away layer after layer of the uppermost strata, revealing the older rocks beneath. In this way, a bit of the long-buried riverbed and its fossil treasure began to show up on the top of a jagged ridge.
Not far from that ridge, the prehistoric Fremont people carved elaborate drawings into the cliffs about 1000 A.D. Fur trader William H. Ashley floated down the Green River not far from that ridge in 1825. Explorer-scientist John Wesley Powell followed the same route in 1869. But it remained for Earl Douglass to take a close enough look at the ridge to notice what was weathering out on its surface. Douglass, a paleontologist from the Carnegie Museum in Pittsburgh, Penna., had not come here by accident. He knew that similar rocks in Colorado and Wyoming had yielded great dinosaur finds, and he began to search this area in 1908, On August 17, 1909, he wrote in his diary: 'At last in the top of the ledge
... I saw eight of the tail bones of a Brontosaurus in exact position. It was a beautiful sight." Those were the first of thousands of bones, including several nearly complete skeletons, that Douglass and his workers dug from this single ridge. Many of them are now on display in the Carnegie Museum.
The quarry site was designated a national monument in 1915, and though Douglass continued to excavate for several more years, he did not remove everything. Today the remainder of the bone-bearing layer forms one wall of the Dinosaur Quarry building. Here the fossil bones are still being exposed in but not removed from, the sandstone face, creating a unique exhibit of the bones in their natural setting. In the summer, you can watch the Quarry paleontologists as they expose the fossils in high relief.
The canyons of the Green and Yampa Rivers were added to the original park in 1938, but, isolated from main-traveled routes and perhaps overshadowed by the uniqueness of the Quarry, they have remained relatively unexplored. A few hardy souls settled in the canyons around the turn of the century, but most of the land is still wilderness.
Erosion has stripped away the "younger" rocks from most of the canyon country, accentuating the contrast, in both time and environments, between past and present. Land that was once a seafloor where corals and shellfish thrived is now far away from moist ocean winds, and a semi-desert climate prevails. The temperature can vary by nearly 85§C (155§F) between January and July, and though snow cloaks the ground in winter, it contains little water. Rain, when it comes, is often in the form of brief, localized thundershowers, drenching the ground in one place and filling the gullies with flash floods, while dust devils rise in the hot breeze nearby. In this setting, life must be tolerant of extremes. Good looks, as humans rate them, are not very important in the desert. Most of the dry basin-and-plateau land of the park is covered with sagebrush, greasewood, and saltbush, graduating into "pygmy forests" of pinyon pine and juniper at the higher elevations. Drab as these plants may seem to our eyes, they are beautifully adapted for their special tasks: conserving water, resisting extreme temperatures, and eking out a living from poor soils.
Within this arid setting, the rivers and their canyons are linear oases, in which the green of cottonwoods and boxelders seems all the more vivid in contrast to the surroundings. Boaters drifting along a quiet stretch of water may be startled by the sound of a flock of Canada geese taking wing, or by the sight of a bighorn sheep high on a cliff. Around the next bend might be a surprise of another kind, as the river plunges madly into a foaming rapid. Roar - bounce - splash!- who would have expected this in the middle of the desert?
Perhaps the unexpected is what Dinosaur National Monument is all about - a gallery of dinosaur bones in solid rock, the whisper of flowing water heard from a sun-baked canyon rim, the aroma of Douglas-fir on the high mountain slopes. Time and the rivers have been long at work on this land. Take the time to discover its secrets.
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