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Colorado

National Monument

Colorado

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park geology subheading
Wingate Sandstone forms Independence Monument (tower in center of photo) and the surrounding canyon walls.
Colorado National Monument, Colorado

Pretend you are watching a movie about the shaping of this landscape over eons of time. The Earth's surface recurringly rises and falls, crumbles, and blows away. The higher the land rises, the faster it is carried away by wind and rushing water, dictated by the constant pull of gravity. You see buckling, folding, and cracking of the surface caused by tremendous uplifts from deep within the Earth. This is matched by equally dramatic forces of erosion at work on the surface.

The last quarter of this imaginary movie depicts the events that show up today in the rocks of Colorado National Monument. The Uncompahgre Highland rises to mountainous heights, then is worn down over millions of years to a nearly level plain. (These ancient crystalline rocks - granite, gneiss, schist - which were at the core appear today in the canyon floors.) Great bodies of water follow, depositing layer upon layer of soft, sedimentary rocks as distant mountains give themselves up, grain by grain, to be reformed.

Becoming entombed within the rock are the remains of dinosaurs, fish and shellfish, early mammals, and many other life forms that lived within a span of more than 100 million years. Finally the Rocky Mountains begin their slow rise, and the surrounding land is raised as well. Water falling as rain and snow invades rock crevices, expands as ice, and begins prying pieces loose from solid material. As erosion continues, the streams and rivers sort themselves out into the ancestral Colorado River system.

Volcanic eruptions, the latest series of geological events, spread molten lava over much of the land nearby. (The remnant lava today forms a resilient cap on the Grand Mesa to the northeast.) Then, in the final frames of the geologic movie, humans arrive. They begin living in this broken, arid landscape, searching for plants and game to feed their families.

Time and weather have scoured away great volumes of these rocks, remnants of which form today's dramatic landscape. The rocks' differing resistance to erosion has given rise to the varied landforms - here a rounded slope, there a sheer cliff, and beyond, a towering monolith - that grace the park. More than for any other reason, Colorado National Monument was established to preserve these scenic treasures. Fossils and other evidence help to date these rock layers which spread across many other areas of the southwest. Here, with the exception of those exposed on the deeper canyon floors, all the rocks were formed at various times during the Mesozoic Era, 225 to 65 million years ago, dominated by the life forms we know as dinosaurs, perhaps not reptiles at all, but a form of life ancestral to today's birds. A fossil dinosaur skeleton from a site near the park created quite a stir among scientists at the turn of the century when it was found to be of the largest species ever discovered.

Black and white photo of paleontologist
Paleontologist carefully chips rock matrix from a column of dinosaur vertebrae.

 

Detailed Park Geology

The Colorado Plateau and its desert landscape covers parts of Colorado, Utah, Arizona, and New Mexico, including Utah’s canyonlands and the Grand Canyon. As one heads west, however, this spectacular region has its most visible beginnings on the western Grand Junction skyline in Colorado National Monument (Carpenter, 2002).

Over a period of 1.7 billion years, geologic processes have created the features at Colorado National Monument. These processes include volcanism in island arcs along the growing ancestral North American continental margin, high-grade metamorphism, several periods of mountain-building, several periods of deep erosion, deposition of marine and non-marine sediments, more uplift, and finally erosion that carved the modern landforms (Scott et al., 2001).

Colorado National Monument lies along the northeastern flank of a large topographic feature known as the Uncompahgre Plateau. It is a high, elongated plateau region that extends from Ridgeway, Colorado, northwestward to near Cisco, Utah. The metamorphosed crystalline basement rock (1.7 billion years old), as seen in the monument, underlies the entire length of the plateau, with the Triassic Chinle Formation resting directly on the ancient basement rocks. There is no hint of the existence of any rocks having been deposited on the eroded basement surface between Late Precambrian and Late Triassic time, a period of some 1.5 billion years (Baars, 1998).

During Precambrian time, island arc volcanic rocks and related sediments accumulated along the continental margin. Compressive mountain building and intrusion of granitic rock and pegmatite dikes followed. During Cambrian through Mississippian time (545-320 million years ago), relatively thin marine sandstone, limestone, dolomite, and shale were deposited, covering much of the North American craton. During Pennsylvanian and Permian time (320-251.4 million years ago), Colorado was subject to a second period of compression and uplift, which formed the Ancestral Rocky Mountains. During this period of mountain building, the previously-deposited marine rocks—if ever present here—were eroded, transported, and deposited away from the monument area in great thicknesses into the Paradox Basin. Once again, the highly metamorphosed cores of ancient mountains lay exposed in the monument area.

Then deposition began again. Triassic through Cretaceous sediments were deposited over Colorado, this time under largely non-marine conditions until the Late Cretaceous seas covered the area. During the Mesozoic, non-marine sandstone and shale were deposited on the Precambrian basement rock. Most of the cross-bedded sandstone was deposited in desert conditions, and commonly shale was deposited in shallow non-marine lakes. Then the thick marine Mancos Shale and younger non-marine sandstone and shale covered these strata.

For a third time, mountain building affected Colorado. The Laramide Orogeny began in Late Cretaceous time (about 70 million years ago) and continued into the middle Eocene (about 50 million years ago). This mountain-building episode caused uplift, folding, and faulting in the Colorado Plateau region. Most of the present-day structural framework for Colorado National Monument was formed during the Laramide Orogeny.

After the Laramide Orogeny, during a significant part of the Cenozoic Era, great volumes of sedimentary rocks—particularly the soft, easily eroded shale—were slowly removed from the Colorado Plateau. During periods of relative tectonic quiescence, rivers in the area tended to meander and began to carve broad valleys into the areas underlain by Mancos Shale, such as Grand Valley. Regional uplift(s) in the Late Cenozoic caused rivers to entrench their meanders into the more resistant rocks beneath the Mancos Shale, forming such notable features as the Grand Canyon, Westwater Canyon, and the Goosenecks of the San Juan River.

This process of exhumation as a result of regional uplift is continuing today. Erosion of the canyons on the northeastern edge of the Uncompahgre Plateau at Colorado National Monument is beginning to remove the Mesozoic rocks from the Plateau. And for a fourth time, Precambrian rocks are being exposed. It is the canyon-cutting process that today is creating the magnificent scenery of Colorado National Monument.

photo of Wingate Sandstone
Wingate Sandstone erodes forming steep cliffs.

 

Colorado National Monument’s magnificent scenery is a result of the process of erosion that creates both its beauty and hazardous conditions. Intense summer thunderstorms are common and quickly produce large volumes of water that rush through the canyons of the monument. These storms erode the canyons, as well as flood buildings and roads built in their paths. Unstable cliffs formed, for example, by the Wingate Sandstone produce rockfalls that pose a threat in areas where visitors travel and that have been destabilized during construction of Rim Rock Drive. Expansive clays, present in rocks in the monument, play a role when wetted, and enhance landslides in the area.


 

References:

Baars, D., 1998, The mind-boggling scenario of the Colorado National Monument—a visitor’s introduction: Grand Junction, Colorado, Canyon Publishers Ltd., 14p.

Carpenter, L., 2002, The geology of the Colorado National Monument: Trail & Timberline, no. 972 (September-October 2002), p. 6-7.

Scott, R.B., Harding, A.E., Hood, W.C., Cole, R.D., Livaccari, R.F., Johnson, J.B., Shroba, R.R., and Dickerson, R.P., 2001, Geologic Formation of Colorado National Monument, in Geologic map of Colorado National Monument and adjacent areas, Mesa County, Colorado: U.S. Geological Survey Geologic Investigations Series I-2740, p. 26-28.



park maps subheading

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.

photo album subheading

A geology photo album for this park can be found here.

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

books, videos, cds subheading

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.



geologic research subheading

Information about the park's research program is available on the park's research webpage.

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.



selected links subheading

NPS Geology and Soils Partners

NRCS logoAssociation of American State Geologists
NRCS logoGeological Society of America
NRCS logoNatural Resource Conservation Service - Soils
USGS logo U.S. Geological Survey

teacher feature subheading

Currently, we do not have a listing for any park-specific geology education programs or activities.

For resources and information on teaching geology using National Park examples, see the Students & Teachers pages.
updated on 01/04/2005  I   http://www2.nature.nps.gov/geology/parks/colm/index.cfm   I  Email: Webmaster
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