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Geological Terms Beginning With "U"



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Ultrabasic Rock

Ultrabasic Rock

An igneous rock with a very low silica content and rich in minerals such as hypersthene, augite and olivine. These rocks are also known as ultramafic rocks.

Ultramafic Rock

Ultramafic Rock

See Ultrabasic Rock.

Unconformity

Unconformity

A contact between two rock units of significantly different ages. An unconformity is a gap in the time record for that location.

Unconsolidated

Unconsolidated

A term used when referring to sediment that has not been lithified into a rock. Uncemented.

Uniformitarianism

Uniformitarianism

A basic geologic principle. Processes that act upon the Earth today are the same processes that have acted upon it in the past. The present is the key to the past.

Unit Cell

Unit Cell

The smallest sample of a substance that has a complete representation of its atomic structure. A crystal structure is formed by repetition of the unit cell in three dimensions.

Uplift

Uplift

A structurally high area in Earth's crust. Formed by movements that bend the crust into a structure such as a dome or an arch.

Upwelling

Upwelling

Movement of cold water from the floor of a lake or ocean up into a shallow area.

U-shaped Valley

U-shaped Valley

A deep valley with a flat floor and very steep walls. Shaped in cross-section like the letter "U". Valleys with this geometry are frequently cut by a glacier.



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