Aa
A type of basaltic lava usually characterized by high viscosity resulting in a rough, broken, rubbly appearance to the resulting lava flow.

Abdomen
The hindmost of the three subdivisions of an insect's body, or the two subdivisions of a spider's body.

Abstract
When describing rock art, these are designs that may be geometric, free form, or non-representational images.

Accidental
A species that has appeared in a given area only a very few times and whose normal range is in another area.

Adit
A horizontal or nearly horizontal passage from the surface into a mine.

Advanced Trail
An advanced trail is a longer route requiring five to 10 hours round trip, with difficult terrain involving extensive route finding.

Aerie
A nest located on a cliff or high place, usually built by a raptor, a bird of prey.

Aestivation
Dormancy during summer or dry season.

A-Frame Tent
This type of tent is simple, light, and often inexpensive. They require staking. Headroom and elbowroom is limited.

Agave
A desert plant with a spike-like flower, similar to a Yucca plant.

AGRC
Automated Geographic Reference Center.

Alcove
A cave-like hollow in a canyon wall.

Alkali Flat
A level area or plain in an arid or semiarid region, usually low-lying with poor drainage, encrusted with alkali salts that became concentrated by evaporation; a salt flat. See also playa.

Alluvial Fan
A fan-shaped deposit of alluvium typically built where a stream leaves a steep mountain valley and runs out onto a level plain.

Alteration
Any physical or chemical change in a mineral or rock subsequent to original formation; usually results in the formation of new minerals or in textural changes in the rock.

Amphitheater
A very large concave hollow in a canyon wall.

Anasazi
This is a Navajo word that is said to mean "ancient ones" or "enemies of our ancestors." It is used to describe the ancient culture of the Four Corners Region. Ancestral Puebloan or Hisat'sinom are now the preferred terms for this culture.

Anasazi Style
Rock art created by the Anasazi Culture, possibly from 100 B.C.E. to C.E. 1450. Located mainly in the Four Corners Region. More recently termed Ancestral Puebloan Style.

Ancestral Puebloan
See Anasazi.

Annual
A plant that germinates, flowers, and sets seed in a single growing season.

Antenna
One of a pair of sensory appendages on each side of an insect's head.

Anterior
Located toward the head.

Anthodite
Gypsum or argonite radiating in clusters of long needle or hairlike crystals on the roof or wall of a cave.

Anthropomorphs
When discussing rock art, these are images that portray human characteristics.

Anticline
A fold in the strata of the Earth that is convex upward (shaped like an A) with the oldest rocks in the center.

Antler
Bony structure protruding from the forehead of members of the deer family.

Aquatic
An animal living in, or a plant growing in, water.

Arboreal
A tree-dwelling bird.

Archaeo-astronomy
The astronomy of ancient cultures. A field of science that studies solar calendars and other relationships between ancient cultures and the sky. A combination of archaeology and astronomy.

Archaic
(6500-1500 B.C.)
Archaic people hunted and gathered wild food, adjusting to a warmer, drier climate. They used natural shelters and temporary structures as homes, traveling seasonally to find resources. Hunters at this time used atlatls (spear throwers) and darts as weapons.

Arete
A saw-tooth ridge formed between adjacent cirques.

Arroyo
The channel of an ephemeral or intermittent stream in the semiarid Southwest, usually with a flat-floor and vertical banks of unconsolidated material two feet or more high. Sometimes called a wady.

Artifact
An object made or used by humans.

ATV
All Terrain Vehicle.