Further Reading

Grabau, Amadeus W. "The Polar-Control Theory of Earth Development." Association of Chinese and American Engineering Journal 18 (1937): 202-223.

-. "Fundamental Concepts in Geology and Their

Bearing on Chinese Stratigraphy." Geological Society of China Bulletin 16 (1937): 127-176.

-. "Revised Classification of the Palaeozoic Systems in the Light of the Pulsation Theory." Geological Society of China Bulletin 15 (1936): 23-51.

granite, granite batholith A coarse-grained igneous plutonic rock with visible quartz, potassium, and plagioclase feldspar, and dark minerals such as biotite or amphibole is generally known as granite, but the International Union of Geological Scientists (IUGS) define granite more exactly as a plutonic rock with 10-50 percent quartz and the ratio of alkali to total feldspar in the range of 65-90 percent.

Granites and related rocks are abundant in the continental crust and may be generated either by melting preexisting rocks or, in lesser quantities, by differentiation via fractional crystallization of basaltic magma. Many granites are associated with convergent-margin or Andean-style magmatic arcs, and include such large plutons and batholiths as those of the Sierra Nevada batholith, Coast Range batholith, and many others along the American Cordillera. Granites are also a major component of Archean cra-tons and granite greenstone terranes.

Many building stones are granitic, since they tend to be strong, durable, and nonporous and exhibit many color and textural varieties. Granite often forms rounded hills with large round or oblong boulders scattered over the hillside. Many of these forms are related to weathering along several typically perpendicular joint sets, where water infiltrates and reacts with the rock along the joint planes. Three sets of perpendicular joints define cubes in three dimensions; large blocks get weathered out and eventually rounded as the corners weather faster than the other parts of the joint surface, since they have more surface exposed to weathering agents. Granite also commonly forms exfoliation domes, in which large sheets of rock weather off and slide down mountain sides and inselbergs, isolated steep-sided hills that

Images Weathering Along Joint

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