Dinosaur

National Monument

Colorado/Utah

Aerial photo of Dinosaur Naitonal Monument

Dinosaur National Monument, Colorado

Dinosaur National Monument is the legacy of rivers, both 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.

The tip of Harpers Corner looks down at the rivers far below. The gaze spans time as well as space. In the rocks beneath 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, Stegasaurus, and other vegetarians, as well as 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 floodwaters 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 riverbed 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 lifting 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, Pennsylvania, 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. However, they are isolated from main-traveled routes and perhaps overshadowed by the uniqueness of the Quarry, and remain 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 sea floor where corals and shellfish thrived is now far away from moist ocean winds, and a semi-desert climate prevails.

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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The General park map handed out at the visitor center is available on the park's map webpage.

For information about topographic maps, geologic maps, and geologic data sets, please see the geologic maps page.

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A photo album for htis park can be found here.

For information on other photo collections featuring National Park geology, please see the Image Sources page.

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Currently, we do not have a listing for a park-specific geoscience book. The park's geology may be described in regional or state geology texts.

Please visit the Geology Books and Media webpage for additional sources such as text books, theme books, CD ROMs, and technical reports.

Parks and Plates: The Geology of Our National Parks, Monuments & Seashores.
Lillie, Robert J., 2005.
W.W. Norton and Company.
ISBN 0-393-92407-6
9" x 10.75", paperback, 550 pages, full color throughout

The spectacular geology in our national parks provides the answers to many questions about the Earth. The answers can be appreciated through plate tectonics, an exciting way to understand the ongoing natural processes that sculpt our landscape. Parks and Plates is a visual and scientific voyage of discovery!

Ordering from your National Park Cooperative Associations' bookstores helps to support programs in the parks. Please visit the bookstore locator for park books and much more.

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For information about permits that are required for conducting geologic research activities in National Parks, see the Permits Information page.

The NPS maintains a searchable data base of research needs that have been identified by parks.

A bibliography of geologic references is being prepared for each park through the Geologic Resources Evaluation Program (GRE). Please see the GRE website for more information and contacts.

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