Geologic Feature


Slate occurs when tectonic plates collide, creating heat and pressure that metamorphize the elements of which the plates are composed. Slate is the metmorphic form of shale, and occurs rather early in the metamorphic process. Slate that continues to be subjected to tectonic pressure results in phyllite, a higher, or denser and finer, grade of rock. In the U.S. Southwest, the occurrence of slate is relatively rare, as many rock formations are the result of geologic processes further along the metamorphic scale from the slightly early production of slate, resulting in a range if schist, gneiss, and ultimately granite, the primary component of much the Southwest's mountainous terrain.

Slate's lower grade makes it easy to use, because it fractures, or cleaves, easily into long, flat plates. Slate is also an attractive stone that can be found in muted colors of blue, black, green, gray and purple.

Shiprock formation, New Mexico

A volcanic rock formation located in San Juan County, New Mexico, on the Navajo Nation Reservation. The actual rock is approximately 10 miles southwest of the town that was named after it, Shiprock. This formation, known to the Navajo as tse bida’hi, meaning “winged rock,” is approximately 1,400 feet in height. The English name “Ship Rock” was coined by Captain J.F. McComb from the U.S. Geologic Survey in 1860 due to its resemblance to a 19th century clipper ship.

In Navajo mythology, this dramatic rock formation is the home of Rock Monster Eagle (Tsé nináhálééh). In some stories, the Rock Monster Eagle swooped down to carry people to the precipice of the formation in order to feed his nestlings. As the tale goes, Monster Slayer killed the Rock Monster Eagle and transformed his children into the ancestors of the golden eagle and the owl.

Tovar Mesa, Arizona

Tovar Mesa is located at the southern edge of the Hopi Indian Reservation, within the boundaries of the Navajo Nation Reservation in northeastern Arizona. It is part of an extensive chain of mesas and desert rock formations that characterize the area.

Cave of the White Cliffs

The White Cliffs are a central reference point in Zuni mythology regarding the food fight and wasteful frolic at Ha'-wi-k'uh. There was enough corn piled about to stuff all the hollow trees, caves and crannies of the White Cliffs yet none was spared for the Corn Maidens who came dressed as beggarly elderly women. The A'shiwi, or Zuni, were not just squandering their abundance but lacking in generosity of spirit as well. The tale "The Origin of the Dragonfly and of the Corn Priests, or Guardians of the Seed" is recounted by Frank Hamilton Cushing in the late 1800s and later written as the children's story The Boy Who Made Dragonfly by Tony Hillerman.

Coconino Rim, Arizona

The Coconino Rim is a common name for the rim of the southern portion of the Colorado Plateau in Arizona, within the Coconino National Forest. It is part of the Mogollon Rim Ranger District and reaches 2000 feet in height in some areas. From this viewpoint, one can see the vast scenery and landscape of Arizona.


An undercut is a rock formation that develops when a body of water erodes the base of a rock. This erosion results in an overhanging top layer of rock that protrudes past the lower layer of the rock. In the desert, these may exist in areas where there was once water, or where the water is impermanent and irregular.

water table

The water table is the line between groundwater and unsaturated ground. Beneath the water table the soil, rock, and sediment are saturated with water, whereas above it, they are not, this is called the zone of aeration. The water table fluctuates based on the seasons, rain levels, droughts, and other environmental factors as well as from man-made ones such as the over-use of well water.

Big Mountain, Arizona

The most noticeable geologic formation in Black Mesa, Arizona. This mountain, called Dził Ntsaaí in the Navajo language, translates to "Extensive Mountain" in English. Big Mountain is a sacred Navajo site that appears in many stories, prayers, ceremonies, and has long been a place for gathering natural materials used for medicine and healing. According to tradition, Navajos believe that their creator and creation story placed them specifically in their land, which is located near Big Mountain.

In more recent history, Big Mountain has become a site of dispute, as it was the dividing line between the Hopi and Navajo Joint Use Area. Many Navajos have been displaced and relocated from this land that they consider sacred.

volcanic tuff

A type of sedimentary rock that is characterized by its layered, grainy appearance. Tuff consists of a mix of fine-grained rock and condensed volcanic ash that have been meshed and pressed together after a volcanic eruption. Tuff often appears porous, and is subject to changes in formation over time as a result of exposure to wind, water, or ice.

Note that tuff is the correct spelling of this type of rock, although in the novel People of Darkness it is spelled volcanic tuft.

geological formation

In the study and mapping of the earth's surface, geologists classify a geological formation as any basic unit of rock that stands out from its surroundings. A geological formation, therefore, can be small or very large, but must be distinct in appearance as well as substantial enough to chart on a map. Geological formations are often given names based on their location and their dominant rock type. For example, the El Malpais sandstone bluffs are a unique formation of sandstone, located in the El Malpais National Monument near Grants, New Mexico.


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