Orogeny

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Related to Alpinotype orogeny: orogenesis, orogenic

orogeny

[ȯ′räj·ə·nē]
(geology)
The process or processes of mountain formation, especially the intense deformation of rocks by folding and faulting which, in many mountainous regions, has been accompanied by metamorphism, invasion of molten rock, and volcanic eruption; in modern usage, orogeny produces the internal structure of mountains, and epeirogeny produces the mountainous topography. Also known as orogenesis; tectogenesis.

Orogeny

 

the process of the formation of mountains resulting from vertical tectonic movements, whose rate exceeds that of the exogenous process of destruction and removal (erosion) of rock or the process of buildup of sediments (accumulation), which lead to the leveling of the earth’s surface. Orogeny is characteristic of active regions of the earth.


Orogeny

 

(also orogenesis), a geological term introduced by the American geologist G. Gilbert in 1890 to designate mountain building and intense deformation by folding and faulting. Gilbert singled out orogenic movements of the earth’s crust and contrasted them to epeirogenic movements, that is, slow upward and downward movements.

The concept of orogeny was further developed by the French geologist G.-E. Haug, who in 1907 proposed that orogeny be distinguished only within geosynclinal regions. Subsequently, in 1919, the German geologist H. Stille hypothesized that the chief result of orogeny was not the formation of mountains but rather the formation of folds.

When the term “orogeny” was introduced, the crumpling of layers of rock into folds was believed to lead directly to the formation of mountains. It was later discovered that mountains are not created by folding of the earth’s crust and that mountain formation often occurs independently of folding. Soviet geologists thereupon began using the term “orogeny” to designate only the process of mountain formation. They made a distinction between epigeosynclinal (postfolding) orogeny and epiplatform orogeny, which is not preceeded by geosynclinal subsidence and folding-overthrust deformation. Outside the USSR, orogeny is still often understood in the Stille interpretation, that is, as the aggregate of fold and mountain formation.

V. E. KHAIN