rock summary

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Below is the article summary. For the full article, see rock.

Slate, a metamorphic rock, showing typical splintery fracture and thin layering (slightly larger than life-size).

rock, In geology, a naturally occurring and coherent aggregate of minerals. The three major classes of rock—igneous, sedimentary, and metamorphic—are based on the processes that formed them. These three classes are further subdivided on the basis of various factors, especially chemical, mineralogical, and textural attributes (see e.g., acid and basic rocks; crystalline rock; extrusive rock). See also felsic rock; intrusive rock; mafic rock.

Figure 1: Interrelationships of salt structures (see text)

salt dome Summary

Salt dome, largely subsurface geologic structure that consists of a vertical cylinder of salt (including halite and other evaporites) 1 km (0.6 mile) or more in diameter, embedded in horizontal or inclined strata. In the broadest sense, the term includes both the core of salt and the strata that

loess Summary

Loess, an unstratified, geologically recent deposit of silty or loamy material that is usually buff or yellowish brown in colour and is chiefly deposited by the wind. Loess is a sedimentary deposit composed largely of silt-size grains that are loosely cemented by calcium carbonate. It is usually

coal Summary

Coal, one of the most important primary fossil fuels, a solid carbon-rich material that is usually brown or black and most often occurs in stratified sedimentary deposits. Coal is defined as having more than 50 percent by weight (or 70 percent by volume) carbonaceous matter produced by the

fold Summary

Fold, in geology, undulation or waves in the stratified rocks of Earth’s crust. Stratified rocks were originally formed from sediments that were deposited in flat horizontal sheets, but in a number of places the strata are no longer horizontal but have been warped. Sometimes the warping is so