Glossary Database

Select a Letter to view the associated terms.
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

 Glossary Term: 

Definition:

 Ultimate phalange  The last digit.
 Ultramafic rock  An igneous rock composed entirely of ferromagnesian minerals.
 Ultraviolet radiation  That part of the electromagnetic spectrum ranging in wavelength from 0.2 to 0.4m m. Just past the visible violet spectrum.
 Unconfined aquifer  An aquifer with no confining geologic structure on the aquifer (aquifer pressure about the same as atmospheric pressure).
 Unconformity  A discontinuity in the succession of rocks, containing a gap in the geologic record. A buried erosion surface. See also nonconformity.
 Unconsolidated  Loose earth material such as gravel, sand, or lava that hasn't solidified yet.
 Ungulate  a term that refers to hoofed animals. This includes Family Cervidae (deer) and Bovidae (sheep and goats) as well as the pronghorn. They typically have antlers or horns and are herbivores.
 Uniformitarianism  The theory that geologic events in the past were caused by natural processes which are operating at the present time.
 Unsaturated zone  The zone below the surface and above the water table, in which pore spaces are usually filled with air. Synonymous with phreatic zone.
 Uplift  A structurally high area in the crust, produced by movements that raise the rocks, as in a broad dome or arch.
 Upwarp  An arched or uplifted segment of the crust. Synonymous with uplift.
 Urostyle  A rod-like bone composed of fused tail vertebrae, present in frogs and toads (Halliday 1987).
 U-shaped valley  A valley with a U-shaped cross-section caused by glacial erosion. Contrast with the V-shape of a typical stream valley.
 Uterus  the hollow muscular organ in female mammals in which the fertilized ovum usually becomes embedded, and in which the developing embryo and fetus are nourished (Morris 1992).