North of the Grand River is a wide valley, in which are Cretaceous rocks, the bluffs bordering it being of upper Cretaceous age, beyond which are the Tertiary strata, forming the “Book” or “Roan” Mountains, which are in reality a series of plateaus, one above the other, with cliff-like edges, forming, in other words, a series of terraces.
Annual Report for 1875 (Hayden 1877, 35)
The Little Book Cliffs of this landscape drawing are nothing more than the far eastern end of the Book Cliffs landform that stretches from the eastern edge of the Grand Valley near Palisade to the San Rafael Swell 140 miles to the west in Utah. This landform is a classic of western geology. The seemingly endless stretch of the stratigraphic sequence of the rocks is visible from miles away and follows the modern traveler along Interstate 70 as it leaves Colorado and makes its way deep into Utah.
The artist has labeled some of the sedimentary beds with names of rock formations often found in the Front Range area of Colorado—the Fox Hills and Laramie formations. To modern geologists these are geologic misnomers although the dates for these formations are essentially correct. The formation that caps the dominant cliffs is really the Mesaverde formation that occurs throughout western and southwestern Colorado. In spite of the fact that the naming of the formations is incorrect in modern geologic parlance, the stratigraphy of the cliffs is straightforward and relatively uncomplicated. This is pointed out by Dr. A. C. Peale, the geologist in charge of this division of the Hayden Survey for the summer of 1876. He states unequivocally, “Fortunately the geological structure is so simple that a good idea of the areas occupied by the various formations was obtained during our hasty trip along the crest, and no difficulty was experienced in coloring the geologic map” (Hayden 1878, 170).
The name “Book Cliffs” is a not very subtle double entendre. The first meaning comes from the look of the flat-lying strata—the hard, resistant Mesaverde formation overlying the soft Mancos formation below. The edges of these formations look like the pages of a book lying on a slightly tilted desk. The second meaning is that this is such a good and obvious example of sedimentary rock structure without folds or faults that the geology is laid out like an easily read book—the slightly ambiguous naming of the formations notwithstanding.
The Grand Valley is a valley in part because of the erosion and transport of large amounts of sediment by the Colorado River (formerly called the Grand River) and its tributaries. But even more critical has been the major uplifts of the region especially during the Miocene and Pliocene epochs. Just east of the Grand Valley near De Beque there was at least 3,600 feet of uplift and displacement as confirmed by the offsetting of a basalt flow that is 10 million years old. For the Grand Valley itself, the valley floor lies thousands of feet below both the Book Cliffs on the north and the Colorado National Monument (part of the much larger Colorado Plateau) to the south. The Book Cliffs have been displaced considerably from the valley bottom, but in comparison to the Colorado Plateau uplift, the Book Cliff uplift was minimal. The Colorado Plateau in the area of the Colorado National Monument has been raised an additional 6,700 feet higher than the Book Cliffs across the valley. We know this because the geologic formations of the Monument are the same rocks that are buried thousands of feet below the top of the Mesaverde formation of the Book Cliffs.
Even with the evident simplicity of the geology of this area as expressed by Dr. Peale, there was confusion in naming these landforms. For example in the section title for the Annual Report for the field season of 1876 that discusses the Book Cliffs, Peale uses the term “Roan Cliffs” interchangeably with the term “Book Cliffs.” Modern geologic maps do use Roan Cliffs as a name, but this is for the cliff edge of a higher plateau that sits above the Book Cliffs and is found to the north and east; the Roan Cliffs belong to the Tertiary age, which is younger than the Cretaceous aged Book Cliffs and its geologic formations.
Both of these cliffs and their respective formations, however, are windows on the fossil fuel resources locked in the rocks. In the case of the Book Cliffs, the Mesaverde formation is the main coal-bearing rock for much of western Colorado. In the past, coal was mined out of the Mesaverde from Crested Butte to Redstone and is currently being mined from the Mesaverde near Craig and Hayden in the northwest of the state.
The nearby Roan Cliffs and the Roan Plateau are currently the site of much more of the fossil fuel action in the state. The plateau is composed in large part by the Green River formation. Two different, yet related, fossil fuel enterprises are occurring here today. First, there are very large natural gas deposits locked in the rocks of the Green River formation. Much of the land of the plateau is managed by the United States Bureau of Land Management (BLM) and hundreds of gas (and to a lesser extent oil) leases are being distributed by the BLM. There is considerable controversy over these leases. Much of the Roan Plateau region is considered wilderness—not the high mountains and forests of other Colorado wilderness areas but high plateaus with large amounts of sage and cut by deep canyons that provide excellent wildlife habitat. One emerging and severe problem for many land owners is the practice of hydraulic fracturing (fracking) that is used to release the tightly held natural gas from the rock. Intense pressure is exerted in the drill holes by a mixture of water and a multitude of chemicals to fracture the rock and free the gas. These fractures are starting to impact surface and well water in the region. So far there has been little regulation of this practice that has already affected many residents.
The second fossil fuel enterprise is also controversial and, as yet, untapped. The Green River formation in general and a member of it called the Mahogany Ledge in particular contain vast amounts of what is called oil shale. The oil in this shale is really a near-oil substance called kerogen that needs large amounts of heat and/or pressure to turn it into usable oil. No one has solved all of the economic and especially environmental and water concerns to get the “oil” out. The elusive promise of a new Saudi Arabia here in Colorado is understandably great. But the technical and ecological problems are equally great; nobody is sure what the future of oil shale holds, but it is probable that energy companies are going to continue to try to get at this potential energy bonanza.
The drawing and photograph were taken from a small hill of Mancos shale that sits across the Colorado River from the cliffs and Mount Garfield just outside of the town of Palisade. It is difficult to tell from the drawing or photo that between this vantage point and the cliffs lies the eastern end of the Grand Valley. The valley at the time of Hayden and his survey was undeveloped and essentially deemed a desert except for the riparian areas of cottonwoods along the river itself. Dr. Peale writes, “The valley is for the most part a desert,” with stunted sagebrush and alkaline soils. He predicts that a “portion of the valley . . . may be reclaimed by irrigation from the Grand River” (170). That modest portion of the valley Peale predicted has blossomed into the fecund orchard and vineyard capitol of Colorado because of massive irrigation from ditches and wells that cover the area from Palisade at the eastern end of the valley to Fruita, some twenty miles west along the Colorado River.
The cultural landscapes of the Grand Valley mirror the growth of the intensive irrigated farming. Row upon row of peach and apple trees intermix with the recent explosion of grapevines—both of these interfinger into the sprawling suburban developments spurred by large doses of sunshine and the moderate temperatures in the valley. It is an intimate landscape that is particularly appealing during the summer months when the geometric green foliage contrasts with the dull gray, nearly bare Mancos shale slopes in the background. The irrigation ditches gurgle with growth-giving water that more and more is being demanded for human, domestic use. As the Hayden Survey rightly pointed out, irrigation could make this valley productive. Little did the surveyors envision the explosion of intensive farming that would take place in the valley. Water is the magic potion that has transformed a barren, clay-clogged landscape into the veritable garden that exists today. But that agricultural water windfall from the Colorado River is under more and more stress (see section 8, on the Grand River from Mt. Bross). This is a recurring scenario throughout Colorado and the West. What was once a sparsely populated rural farmland based on extensive irrigation infrastructure is fast becoming a magnet for people who want inexpensive living in a beautiful environment. Water is the limited and coveted currency of the region, and it will remain so as far into the future as we dare to look.