Chapter III: Introduction (2)

The river also erodes by _hydraulic action_ as loose rock fragments are lifted and moved by the force of the stream’s current. This process is similar to the effect produced when soil is churned up and washed away when water from a garden hose is sprayed on loose earth. The effects of hydraulic action have played an important role in widening the canyon, for recession of the cliffs away from the middle of the canyons has been caused in part by undercutting. Thus, as the soft shale and gypsum beds were removed by the stream, the overlying sandstone formations gradually broke off and fell into the canyon. Once on the canyon floor, most of the slabs and blocks of sandstone were eventually broken up and carried away by the streams as sand and mud. Not all of the boulders have been destroyed in this manner; in places (for example, the Rock Garden) similar boulders are seen today (fig. 34).

WEATHERING AND GRAVITY ADD THE FINAL TOUCH

Most of the energy of the river has been expended in downcutting, for the canyon has apparently been deepened more rapidly than it has been widened. But as the stream gouged its channel deeper into the bedrock, an ever-increasing expanse of canyon wall was exposed to other agents of erosion. Slowly—almost imperceptibly—the walls of the canyon have been eroded by the processes of weathering and mass-wasting.

Weathering.—

Wherever rocks are exposed on the earth’s surface, they are attacked by the agents of _weathering_. They are dissolved by rainwater, pried apart by frost and ice, and blasted by windblown sand. Some of the changes produced by weathering are purely mechanical, that is, the rock is simply reduced to smaller fragments without being broken down chemically or undergoing any change in its mineral composition. This _mechanical weathering_, or _disintegration_, takes place in a number of ways. Changes are especially noticeable in rocks that are subjected to large daily temperature variations. If a crack in these rocks becomes filled with water and the temperature drops below freezing, ice forms. When water freezes it expands by about 10 percent of its volume—this is the reason why water pipes often split open during the winter. Just as in a water pipe, the pressure of the expanding ice is commonly great enough to widen and deepen the crack in the rock. This process, called _frost wedging_, may ultimately cause the rock to split and fall apart. The cumulative effects of frost wedging have probably played a significant role in prying off large blocks of rocks from the walls and rim of the canyon.

Animals and plants may also hasten rock disintegration. Plant roots commonly grow in rock crevices and as the roots become larger they wedge the rock apart. Burrowing animals such as rabbits, gophers, and ground squirrels also promote rock disintegration. Although they do not attack the rocks directly, their digging exposes new rock surfaces to weathering processes. The holes these creatures make also permit water and air to enter the earth more easily, thereby hastening rock destruction.

Man, of course, promotes more rock disintegration than all other animals combined. Thus, as one explores the canyon’s trails and climbs its walls, he will not only see evidence of the various types of mechanical weathering, he will also be contributing to the further wearing away of the rocks.

_Decomposition_, or _chemical weathering_, works hand in hand with mechanical weathering. But unlike disintegration, decomposition produces rock materials that are basically different from the original unweathered rock. These changes are brought about as the result of chemical reactions between minerals in the rocks and water, carbon dioxide, and oxygen. Although the arid climate and severe winters of the Panhandle generally facilitate mechanical weathering, some of the red shales and gypsum deposits show the effect of oxidation, hydration, and other forms of chemical weathering (fig. 10).

Mass-wasting.—

_Mass-wasting_, the erosional process by which rock and soil move downslope in response to the force of gravity, has also been instrumental in shaping Palo Duro Canyon. This type of erosion has been especially active on the walls of the canyon, for here the slopes are steep enough to promote downward movement of earth materials. In a few places there have been landslides which have moved large quantities of rock in a short span of time. But most mass movements have been imperceptibly slow as masses of _talus_ (accumulations of rock debris) on steeper slopes have inched slowly downhill because of their own weight. Talus deposits produced in this way can be seen at the foot of most of the cliffs and erosional remnants throughout the canyon (fig. 20).

Differential erosion.—

Even the most casual observer will soon note that not all of the canyon’s rocks have been equally affected by erosion. Indeed, it is the nature of this _differential erosion_ that gives Palo Duro Canyon the rugged sculptured appearance that accounts for much of its beauty.

Visitors to Palo Duro Canyon commonly ask why the rock formations are so diversely shaped. The answer to this question lies in the rocks themselves. Because the various rock strata are of unequal hardness, they erode at different rates of speed. Hence, the harder, more resistant rocks, such as the sandstones and conglomerates of the Trujillo Formation, form the shelves, ledges, and “caps” of the rock sculptures. The Lighthouse (fig. 31) and other pedestal rocks (fig. 16) are good examples of land-forms produced by differential erosion. The “hoodoos” mentioned earlier are also the products of this type of erosion (figs. 16 and 20).

Softer rocks like shales and clay are more readily eroded and they normally form slopes rather than cliffs or ledges (fig. 12). Grooves, recesses, and caves have also developed in some of the less resistant rocks such as the shales and gypsum beds of the Quartermaster Formation. Catarina Cave (fig. 27) which has formed in the red and white shales of the Spanish Skirts (fig. 26) is a good example of this type of feature. Caves of this type afforded protection to both man and wild animals since the dawn of history, for their remains have been found in a number of similar caves.

Thus, within a relatively short time—geologically speaking—the familiar land-shaping processes described above have joined forces to provide Texas with one of its most remarkable natural attractions. But interestingly enough, the same geologic processes that created these unusual formations are busily at work destroying them. As time passes and erosion progresses, the caps of the pedestals are worn away and the underlying shales crumble and are washed into the valley below. Yet even as the old land-forms are being destroyed, wind, water, ice, and man are attacking the canyon walls to produce still more of these interesting erosional remnants.

WHAT TO DO AND SEE AT PALO DURO CANYON STATE PARK

The visitor to Palo Duro Canyon can choose from a number of recreational and educational activities. Moreover, regardless of whether one visits for a few hours to picnic along the banks of the river, or spends a week at one of the well-kept campgrounds, the visit will probably be both pleasant and rewarding. In the pages that follow there is a brief description of certain of the park landmarks and some of the more popular attractions within the canyon. The numbers in parentheses refer to numbers which designate these places on the map of Palo Duro Canyon (fig. 2, pp. 4-5). Hopefully, this information will help one to plan his visit to the canyon and thereby make his stay more enjoyable and worthwhile.

_Park Entrance_ (1).—

The first stop in the park is the gate at the ranger station (fig. 21). Here one pays a modest admission fee and receives literature and information about the park. The park is open every day of the year, but the entrance gates close at sundown.

_Coronado Lodge and Observation Point_ (2).—

The overlook at Coronado Lodge (fig. 22), located about half a mile from the Park Entrance, is a good place to start one’s visit. Situated on a ledge of Ogallala caliche (p. 26), the Lodge is an attractive, rustic structure constructed of blocks of Trujillo sandstone (p. 22). Its picture windows and outdoor overlook provide a matchless view of the canyon and make it possible to become oriented for the descent to the canyon floor. Large, coin-operated telescopes permit close-up views of distant parts of the canyon, and there are museum cases containing objects of historical and geological interest from the Palo Duro area. If possible one should visit the Coronado Observation Point more than once during the visit, preferably at different times of the day. Because of shifting clouds and changing lighting conditions, the canyon presents a continually changing panorama from sunrise to sunset. Open year-round, the Lodge offers a complete line of souvenirs, film, and camping supplies. There is also a snack bar where coffee, sandwiches, and cold drinks can be purchased.

_The Scenic Drive_ (1-16).—

After viewing the canyon from Coronado Lodge, one should take the scenic drive on Park Road 5. This paved, all-weather road descends the northwest rim of the canyon and continues on to the turnaround at Cow Camp, a distance of about 8 miles. Although the present scenic drive was completed in 1951, the path that it follows is essentially that which was laid out by Colonel Charles Goodnight when he established Palo Duro ranch in 1876. The road descends to the canyon floor in a series of well-engineered turns, but because it drops some 800 feet in little more than a mile it is wise to use second or low gear on the descent. One should also observe the posted speed limits (10 to 20 miles per hour) and keep to the right side of the road at all times.

In the 800-foot drop from rim to floor, the complete geologic section of the canyon is traversed, as one passes from the Pleistocene sands through the Ogallala, Trujillo, and Tecovas Formations, before reaching the Quartermaster Formation which is exposed in the canyon floor. Each of these geologic formations is discussed elsewhere in this publication (pp. 16-28).

_Pioneer Amphitheatre_ (3).—

Upon reaching the canyon floor, Park Road 5 flattens out and from this point it is but a short distance to the Pioneer Amphitheatre, one of the canyon’s newest and most popular attractions. Here, located at the foot of a colorful 600-foot cliff, is a remarkable 1500-seat outdoor theatre of latest design (fig. 23). Each evening during a ten-week summer season, a symphonic drama portraying the history of the Texas Panhandle is presented in the amphitheatre. Information about these productions can be obtained at the Park Entrance, Coronado Lodge, and other points within the park.

_Sad Monkey Train Ride_ (4).—

The Sad Monkey Railroad begins—and ends—at Sad Monkey, Texas, a small “community” that lies at the foot of Triassic Peak (fig. 24). Unlike most miniature railroads, the Sad Monkey Special is not a “kiddie” ride. Instead, this 2-mile journey provides an opportunity to get away from the road for a closer look at the geologic formations exposed along the track. There are especially good views of the Spanish Skirts (fig. 26), Catarina Cave (fig. 27), and Triassic Peak (fig. 25). These, and other features of geologic interest, are pointed out by an experienced lecturer who also presents a brief review of the geologic history of the area.

_Triassic Peak_ (5).—

Long used by Indians and ranchers as a Palo Duro landmark, the canyon visitor will find Triassic Peak to be equally useful as a geologic landmark. When viewed from the Sad Monkey Railroad Terminal, the south face of Triassic Peak clearly reveals three of the four major geologic formations of the canyon (fig. 25).

The lower one-third of the peak consists of deeply furrowed, red and white banded shales of the Quartermaster Formation (p. 17). Overlying the Permian red beds are the brightly colored, multi-hued Tecovas shales of Triassic age (p. 19). The composition of the Tecovas is such that the lower shales tend to weather into relatively gentle slopes with rather smooth surfaces. Triassic Peak is capped by a weather-resistant layer of Trujillo sandstone, and this durable cliff-forming sandstone has served as a protective covering to impede the erosion of the softer rocks of the Tecovas and Quartermaster Formations. Although it has withstood the ravages of time exceedingly well, the large blocks of Trujillo sandstone which litter the flanks and foot of Triassic Peak clearly indicate that weathering and mass-wasting have exacted their toll in the geologic past.

Sad Monkey, Texas derives its name from the prominent mass of Trujillo sandstone at the southern extremity of Triassic Peak. When viewed in the proper perspective—and with the proper amount of imagination—this massive block of sandstone bears a striking resemblance to an aged and saddened monkey.

_Spanish Skirts_ (6).—

Few of the canyon’s features are as well-named as the gaudy Spanish Skirts (fig. 26). The lower part of this multi-colored bluff consists of alternating layers of red and white Quartermaster shale, capped by the colorful maroon and lavender Tecovas shales. Located on the north flank of Timber Mesa, the Spanish Skirts and nearby Catarina Cave can be reached by an easy half-mile path. The trail begins on the west side of Park Road 5, just beyond the Timber Creek bridge located several hundred feet from the Sad Monkey Station.

_Catarina Cave_ (7).—

A short distance west of the Spanish Skirts lies Catarina Cave. This depression has been washed out of the relatively soluble Permian shales (fig. 27).

_Santana’s Face_ (8).—

Like Triassic Peak, Timber Mesa is capped by a thick layer of massively bedded Trujillo sandstone. On the eastern tip of the mesa the sandstone has been eroded in such a fashion that it resembles the profile of an Indian (fig. 28). This feature, called Santana’s Face, is best seen from the park road shortly after leaving Sad Monkey Station.

_The Sky Ride_ (9).—

The Sky Ride, located near the first water crossing on Park Road 5, transports visitors from the canyon floor to the top of Timber Mesa (fig. 28). The 300-foot ascent is made in ski-lift chairs that are comfortable and safe. The observation area atop the mesa offers an unusually fine view of most parts of the canyon.

_The First Water Crossing_ (10).—

As it winds through the canyon, the park road crosses the Prairie Dog Town Fork of the Red River seven times in a distance of about 4 miles. These fords, or water crossings as they are called locally, are paved and are normally safe to pass through. They should, however, be avoided during times of heavy rains and flash flooding. Because of stream erosion, especially fine exposures of the Quartermaster Formation are revealed in the stream banks near several of the crossings.

The first of these crossings (fig. 29) is about 1 mile from the Sad Monkey Station and is one of the more popular picnic areas in the park. This area was also popular with earlier residents of the park, for it is believed to have been the campgrounds of both the Kiowa and Comanche Indians.

_Colonel Charles Goodnight’s Dugout_ (11).—

As mentioned earlier (p. 6) Colonel Charles Goodnight entered the canyon in 1876 with more than 16,000 head of cattle. Although he later established more comfortable quarters, Col. Goodnight first lived in a primitive dugout similar to the one shown in figure 30. A replica of this early shelter has been constructed of mud, stone, and logs and can be seen on the west side of the park road just beyond the first water crossing (_see_ fig. 29).

_The Lighthouse_ (12).—

The unpaved road to the Lighthouse enters Park Road 5 about two-tenths of a mile beyond the first water crossing. Although considered by many to be the canyon’s best-known landmark, the Lighthouse is actually not within park boundaries. It is located in Little Sunday Canyon about 3 miles west of the road and is not easily accessible to the average visitor. Like many of the park’s natural attractions, the Lighthouse is an erosional remnant of colorful Trujillo shales and sandstones (fig. 31). A similar pedestal rock, the Devil’s Tombstone, can be reached by means of a trail which leaves the Lighthouse road and enters Sunday Canyon.

_Capitol Peak_ (13).—

Capitol Peak (figs. 20 and 32) is a rather imposing geologic feature that can be seen from a number of points along Park Road 5. There are especially good views in the vicinity of the second water crossing if one will look to the west of the road. Just beyond the crossing an unimproved road leads to the foot of Capitol Peak. The lower part of this feature is composed of Quartermaster shales of Permian age and the upper section consists largely of Triassic Tecovas shales. When viewed from the proper angle, the silhouette of Capitol Peak is thought to resemble the prostrate form of a human (fig. 32). For this reason it has also been called the Sleeping Indian.

_Fortress Cliff_ (14).—

The Ogallala Formation of Pliocene age (p. 23) forms the upper rim of the canyon and is well exposed in impressive Fortress Cliff (fig. 33). Although this precipitous cliff dominates the eastern rim of the canyon along most of the scenic drive, especially good views are afforded between the second and third water crossings.

_The Rock Garden_ (15).—

Shortly after fording the river at the fifth water crossing, there is a jumbled pile of boulders on the west side of the road (fig. 34). This accumulation of Trujillo sandstone blocks has been named the Rock Garden. Many boulders such as these have accumulated on the floor of the canyon in ages past. However, most of these have been destroyed by weathering and their fragments removed by the canyon’s streams.

_The Devil’s Slide_ (16).—

The Devil’s Slide can be reached by an unimproved road that leads southwest from the scenic drive for a distance of about half a mile. Composed of upper Quartermaster and lower Tecovas shales, the surface of this eroded spur is laced with many trails and “slides” that have been made by previous visitors (fig. 35).

_The Turnaround_ (17).—

A loop marks the end of Park Road 5 and the conclusion of the scenic drive. Located in this area are a number of fine camping areas, picnic grounds, the old stone cottages called the “Cow Cabins,” and rest rooms with shower facilities (fig. 36).

_Hiking._—

There are a number of established trails for the visitor who is interested in hiking. The more popular trails include those to the Spanish Skirts and Catarina Cave (p. 37), the Devil’s Tombstone, the Lighthouse (p. 39), and the Devil’s Slide (p. 40). Park rangers will be glad to provide more complete information about these and other trails within the canyon.

_Horseback riding._—

Saddle horses can be rented at the stables located east of the road near the Pioneer Amphitheatre. There are a number of trail rides that can be taken on well-trained horses accustomed to the rugged terrain of the canyon. Additional information may be obtained from the attendants at the stable.

_Camping and picnicking._—

An ample number of well-developed camping and picnic areas are scattered throughout the canyon. Most are located adjacent to or a short distance from Park Road 5; they are equipped with outdoor fireplaces and tables. Running water, rest rooms, and showers are provided in certain areas. Campsites are available on a first-come first-served basis, and there is a 10-day limit on overnight camping. Detailed information on camping regulations and camping areas is available from a park ranger or at the Entrance Station.

_Photography._—

Palo Duro Canyon offers many opportunities for both amateur and professional photography. The multi-colored rock formations, erosional land-forms, and plants and animals offer limitless possibilities to the creative and imaginative photographer. Color shots are especially effective, but a haze filter will be helpful when photographing distant objects. Morning and afternoon are the best times for picture taking as the mid-day sun is “flat” and lends little perspective to the canyon scene.

PANHANDLE-PLAINS HISTORICAL MUSEUM

The visitor to Palo Duro Canyon State Park would do well to start his visit at the Panhandle-Plains Historical Museum located on the campus of West Texas State University in Canyon (fig. 37). Here all phases of history—recent, archeologic, and geologic—are depicted in the various halls. In the Hall of Pre-History are the fossilized remains and reconstructions of ancient animals that were entombed in the canyon walls as long as 200 million years ago. Elsewhere there are exhibits and dioramas that portray human history in the Palo Duro area. Beginning with the oldest known evidence of human occupation about 12,000 years ago, there is a succession of displays that tell the story of man in the Palo Duro—High Plains region. These exhibits follow man from the early Indians living in stone shelters, to the horse-using nomadic plains Indians who relied heavily on the great herds of bison and who fought a desperate but losing battle to save their homeland from invasion by the white man. Here, too, is the story of the coming of the Spanish conquistadores, the _comancheros_ (_see_ p. 6), and the advent of the anglican settler. All are portrayed by means of artifacts that represent the different cultures of the region’s colorful past.

The major theme of the Museum is the history of the High Plains during the period of the cattle industry of the open range. One entire hall is devoted to the display of saddles, spurs, lariats, barbed wire, branding irons, a chuck wagon, and a life size model of a typical cowboy of the Old West. The Museum also houses one of the nation’s finest collections of guns of the Old West, the Old World, and guns of today. Other highlights include scale models depicting scenes of the Old West, exhibits of typical rooms from pioneer homes furnished with furniture of that era, a fine assortment of antique vehicles, and famous collections of Western art.

The Panhandle-Plains Historical Museum is easily reached from any of the major highways that pass through Canyon. It is open from 9:00 a.m. to 5:00 p.m. weekdays and from 2:00 p.m. to 6:00 p.m. Sundays.

SELECTED REFERENCES[2]

Brand, J. P. (1956) Triassic System, _in_ Eastern Llano Estacado and
adjoining Osage Plains: West Texas Geol. Soc. and Lubbock Geol.
Soc., Guidebook, Spring Field Trip, April 6-7, 1956, pp. 8-9.

Cummins, W. F. (1890) The Permian of Texas and its overlying beds: Texas
Geol. Survey 1st Ann. Rept. (1889), pp. 183-197.

—— (1893) Notes on the geology of northwestern Texas: Texas Geol. Survey
4th Ann. Rept. (1892), pt. 1, pp. 177-238.

Drake, N. F. (1892) Stratigraphy of the Triassic formations of northeast
Texas: Texas Geol. Survey 3rd Ann. Rept. (1891), pp. 225-247.

Evans, G. L. (1949) Upper Cenozoic of the High Plains: West Texas Geol.
Soc. and New Mexico Geol. Soc., Guidebook for Field Trip No. 2,
November 9, 1949, pp. 1-9.

*——, and Meade, G. E. (1945) Quaternary of the Texas High Plains, _in_
Contributions to Geology, 1944: Univ. Texas Pub. 4401, pp. 485-507.

*Frye, J. C., and Leonard, A. B. (1957) Studies of Cenozoic geology
along eastern margin of Texas High Plains, Armstrong to Howard
counties: Univ. Texas, Bur. Econ. Geol. Rept. Inves. No. 32, 62 pp.

*——, and —— (1959) Correlation of the Ogallala Formation (Neogene) in
western Texas with type localities in Nebraska: Univ. Texas, Bur.
Econ. Geol. Rept. Inves. No. 39, 46 pp.

*——, and —— (1964) Relation of Ogallala Formation to the southern High
Plains in Texas: Univ. Texas, Bur. Econ. Geol. Rept. Inves. No. 51,
25 pp.

*Girard, R. M. (1959) Bibliography and index of Texas geology: Univ.
Texas Pub. 5910, 238 pp.

*—— (1964) Texas rocks and minerals: Univ. Texas, Bur. Econ. Geol.
Guidebook No. 6, 109 pp.

Gould, C. N. (1902) The geology and water resources of the eastern
portion of the Panhandle of Texas: U. S. Geol. Survey Water-Supply
Paper 154, 64 pp.

—— (1907) The geology and water resources of the western portion of the
Panhandle of Texas: U. S. Geol. Survey Water-Supply Paper 191, 70
pp.

*Matthews, W. H., III (1960) Texas fossils: An amateur collector’s
handbook: Univ. Texas, Bur. Econ. Geol. Guidebook No. 2, 123 pp.

*Patton, L. T. (1923) The geology of Potter County [Texas]: Univ. Texas
Bull. 2330, 180 pp.

*Reed, L. C., and Longnecker, O. M. (1932) The geology of Hemphill
County, Texas: Univ. Texas Pub. 3231, 98 pp.

*Sellards, E. H., Adkins, W. S., and Plummer, F. B. (1933) The geology
of Texas, Vol. I, Stratigraphy: Univ. Texas Bull. 3232 (August 22,
1932), 1007 pp.

West Texas State University Geological Society (1964) Palo Duro Field
Trip Guidebook: West Texas State Univ. Geol. Soc., Canyon, 18 pp.

—— (1960) Geology of Palo Duro Canyon State Park and the Panhandle of
Texas: West Texas State Univ. Geol. Soc., Guidebook for 1966 SASGS
Annual Field Trip, April 15-17, 1966, 58 pp.

Smith, A. R. (1967) Caves of Palo Duro Canyon: The Texas Caver, Abilene,
Texas, vol. 12, pp. 145-148.

GLOSSARY

Abrasion—erosion of rock material by friction of solid particles moved
by water, ice, wind, or gravity.

Absolute time—geologic time measured in years. Compare with relative
time.

Amphibians—cold-blooded four-footed animals which have gills in youth
and lungs in maturity (e.g., frog).

Anhydrite—the mineral calcium sulfate, CaSO₄. _See_ Gypsum.

Anticline—an arch-like fold in the rocks, with the beds dipping in
opposite directions on the two sides.

Aquifer—a water-bearing layer of porous and permeable rock.

Aragonite—a form of calcium carbonate (CaCO₃).

Archeozoic—the oldest known geological era; early Precambrian.

Bedding plane—the plane of demarcation between two individual rock
layers or strata.

Calcite—a mineral composed of calcium carbonate, CaCO₃.

Caliche—an accumulation of calcium carbonate, commonly white in color,
in the soil profile.

Cenozoic—the latest era of geologic time, containing the Tertiary and
Quaternary Periods and continuing to the present time.

Chert—dense, hard rock of very fine-grained silica, usually in nodular
form. This material is also called flint.

Concretion—a concentration, usually spherical, of mineral matter in
sedimentary rocks, produced by deposits from solution; it is harder
than the surrounding rock.

Conglomerate—a sedimentary rock composed of rounded, water-worn gravel,
usually mixed with sand, and cemented together by another mineral
substance.

Coprolite—the fossilized excrement of animals.

Eolian—pertaining to the erosion and the deposits resulting from wind
action and to sedimentary rocks composed of wind-transported
material.

Epoch—a subdivision of a geologic period, such as the Pliocene Epoch of
the Tertiary Period.

Era—a major division of geologic time. All geologic time is divided into
five eras: the Archeozoic, Proterozoic, Paleozoic, Mesozoic, and
Cenozoic Eras.

Fluorescence—luminescence of a mineral during exposure to radiation
(such as from ultraviolet or X-rays).

Fluvial deposit—sediment deposited by streams.

Formation—a rock unit useful for mapping and distinguished primarily on
the basis of lithologic character.

Fossil—any remains or traces of plants or animals preserved in deposits
of a past geologic age.

Geode—a hollow stone, usually lined or filled with mineral matter.

Geologic age—the age of an object as stated in terms of geologic time
(e.g., a Pennsylvanian fern, Cretaceous dinosaur).

Geologic time—all time which has elapsed since the first known rocks
were formed and continuing until recent, or modern, times.

Geologic time scale—record of the divisions of earth history.

Gypsum—a mineral, hydrated calcium sulfate (CaSO₄·2H₂O). _See_
Anhydrite.

Hoodoo—a form produced by erosion of rock.

Ice age—the Pleistocene Epoch of the Quaternary Period, Cenozoic Era; a
time of extensive glaciation.

Igneous rock—rocks which have solidified from lava or molten rock called
magma.

Joint—a fracture in a rock along which there has been no displacement on
opposite sides of the break.

Joint System—a series of two or more sets of joints passing through a
rock mass and separating it into blocks of more or less regular
pattern.

Mass-wasting—erosion caused chiefly by gravity.

Mesozoic—the geologic era between the Paleozoic and Cenozoic Eras; the
“Age of Reptiles.”

Metamorphic rock—rock formed from igneous or sedimentary rocks that have
been subjected to great changes in temperature, pressure, or
chemical environment.

Metamorphism—the process whereby rocks are changed physically by heat,
pressure, or chemical environment into different kinds.

Mineral—a naturally occurring inorganic substance possessing definite
chemical and physical properties.

Nodule—rounded lump of rock or mineral.

Outcrop—the area where a particular rock formation comes to the surface.

Paleontology—the science which deals with the study of fossils.

Paleozoic—that era of geologic time following the Proterozoic and
preceding the Mesozoic.

Period—a basic unit of the geologic time scale into which the eras are
divided, such as the Pennsylvanian Period of the Paleozoic Era.

Permian—the seventh and last period of the Paleozoic Era.

Pleistocene—the first of the two epochs of the Quaternary Period, and
that which precedes modern time, known as the Great Ice Age.

Pliocene—last and youngest epoch of the Tertiary Period of the Cenozoic
Era.

Proterozoic—youngest era of the Precambrian; follows the Archeozoic Era
and precedes the Cambrian Period of the Paleozoic Era.

Red beds—a general term for red sandstone, shales, etc., which appear to
characterize arid periods in the past.

Ripple marks—wave-like corrugations produced in unconsolidated materials
by wind or water.

Rock—any natural aggregate of mineral matter, usually consisting of a
mixture of two or more minerals.

Sandstone—sedimentary rock composed of cemented sand grains, usually
quartz.

Sediment—material that has been deposited by settling from a
transportation agent such as water or air.

Sedimentary rock—rocks formed by the accumulation of sediments.

Shale—a sedimentary rock formed by the hardening of mud and clay and
usually tending to split into thin sheets or layers.

Silica—an oxide of silicon (SiO₂).

Siliceous—containing or pertaining to silica.

Silt—fine muddy sediment consisting of particles intermediate in size
between clay particles and sand grains.

Siltstone—a very fine-grained sedimentary rock composed of silt grains,
and intermediate between shale and sandstone.

Stratified rocks—sedimentary rocks; those formed in beds, layers, or
strata.

Stratum—an individual layer of rock formation. (Plural, _strata_.)

Superposition, law of—in an undisturbed sequence of rocks younger beds
overlie older beds.

Syncline—a trough-like fold in the rocks, with the beds dipping inward
on either side. _See_ Anticline.

Talus—a mass of rock debris commonly on slopes or at the base of a steep
mountain or cliff.

Topography—the configuration of a land surface.

Unconformity—a break in the sequence of rock formations which separates
younger strata from older ones; caused primarily by removal of older
rocks by erosion before those of a later sequence were laid down.

Weathering—any natural process, mechanical or chemical, whereby rocks
are disintegrated or decomposed into smaller particles and
ultimately into clay and soil.

Index

A
abrasion: 30
Adair, John: 6
“Age of Mammals”: 27
alabaster: 17
ancient man in Palo Duro Canyon: 3
anhydrite: 18
anticlines: 18
Apaches: 1, 3
aquifer: 26
Arapahos: 3
Archeozoic rocks: 13

B
“blow sand”: 28
bottom load: 29
Brazos River: 8
_Buettneria_: 22, 23, 24